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Diffstat (limited to 'src/core/ext/filters/client_channel/lb_policy/xds/xds.cc')
| -rw-r--r-- | src/core/ext/filters/client_channel/lb_policy/xds/xds.cc | 1894 |
1 files changed, 1894 insertions, 0 deletions
diff --git a/src/core/ext/filters/client_channel/lb_policy/xds/xds.cc b/src/core/ext/filters/client_channel/lb_policy/xds/xds.cc new file mode 100644 index 0000000000..e6c94167f6 --- /dev/null +++ b/src/core/ext/filters/client_channel/lb_policy/xds/xds.cc @@ -0,0 +1,1894 @@ +/* + * + * Copyright 2018 gRPC authors. + * + * Licensed under the Apache License, Version 2.0 (the "License"); + * you may not use this file except in compliance with the License. + * You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + * + */ + +/// Implementation of the gRPC LB policy. +/// +/// This policy takes as input a list of resolved addresses, which must +/// include at least one balancer address. +/// +/// An internal channel (\a lb_channel_) is created for the addresses +/// from that are balancers. This channel behaves just like a regular +/// channel that uses pick_first to select from the list of balancer +/// addresses. +/// +/// The first time the policy gets a request for a pick, a ping, or to exit +/// the idle state, \a StartPickingLocked() is called. This method is +/// responsible for instantiating the internal *streaming* call to the LB +/// server (whichever address pick_first chose). The call will be complete +/// when either the balancer sends status or when we cancel the call (e.g., +/// because we are shutting down). In needed, we retry the call. If we +/// received at least one valid message from the server, a new call attempt +/// will be made immediately; otherwise, we apply back-off delays between +/// attempts. +/// +/// We maintain an internal round_robin policy instance for distributing +/// requests across backends. Whenever we receive a new serverlist from +/// the balancer, we update the round_robin policy with the new list of +/// addresses. If we cannot communicate with the balancer on startup, +/// however, we may enter fallback mode, in which case we will populate +/// the RR policy's addresses from the backend addresses returned by the +/// resolver. +/// +/// Once an RR policy instance is in place (and getting updated as described), +/// calls for a pick, a ping, or a cancellation will be serviced right +/// away by forwarding them to the RR instance. Any time there's no RR +/// policy available (i.e., right after the creation of the gRPCLB policy), +/// pick and ping requests are added to a list of pending picks and pings +/// to be flushed and serviced when the RR policy instance becomes available. +/// +/// \see https://github.com/grpc/grpc/blob/master/doc/load-balancing.md for the +/// high level design and details. + +// With the addition of a libuv endpoint, sockaddr.h now includes uv.h when +// using that endpoint. Because of various transitive includes in uv.h, +// including windows.h on Windows, uv.h must be included before other system +// headers. Therefore, sockaddr.h must always be included first. +#include <grpc/support/port_platform.h> + +#include "src/core/lib/iomgr/sockaddr.h" +#include "src/core/lib/iomgr/socket_utils.h" + +#include <inttypes.h> +#include <limits.h> +#include <string.h> + +#include <grpc/byte_buffer_reader.h> +#include <grpc/grpc.h> +#include <grpc/support/alloc.h> +#include <grpc/support/string_util.h> +#include <grpc/support/time.h> + +#include "src/core/ext/filters/client_channel/client_channel.h" +#include "src/core/ext/filters/client_channel/client_channel_factory.h" +#include "src/core/ext/filters/client_channel/lb_policy/xds/client_load_reporting_filter.h" +#include "src/core/ext/filters/client_channel/lb_policy/xds/load_balancer_api.h" +#include "src/core/ext/filters/client_channel/lb_policy/xds/xds.h" +#include "src/core/ext/filters/client_channel/lb_policy/xds/xds_channel.h" +#include "src/core/ext/filters/client_channel/lb_policy/xds/xds_client_stats.h" +#include "src/core/ext/filters/client_channel/lb_policy_factory.h" +#include "src/core/ext/filters/client_channel/lb_policy_registry.h" +#include "src/core/ext/filters/client_channel/parse_address.h" +#include "src/core/ext/filters/client_channel/resolver/fake/fake_resolver.h" +#include "src/core/ext/filters/client_channel/subchannel_index.h" +#include "src/core/lib/backoff/backoff.h" +#include "src/core/lib/channel/channel_args.h" +#include "src/core/lib/channel/channel_stack.h" +#include "src/core/lib/gpr/host_port.h" +#include "src/core/lib/gpr/string.h" +#include "src/core/lib/gprpp/manual_constructor.h" +#include "src/core/lib/gprpp/memory.h" +#include "src/core/lib/gprpp/mutex_lock.h" +#include "src/core/lib/gprpp/orphanable.h" +#include "src/core/lib/gprpp/ref_counted_ptr.h" +#include "src/core/lib/iomgr/combiner.h" +#include "src/core/lib/iomgr/sockaddr.h" +#include "src/core/lib/iomgr/sockaddr_utils.h" +#include "src/core/lib/iomgr/timer.h" +#include "src/core/lib/slice/slice_hash_table.h" +#include "src/core/lib/slice/slice_internal.h" +#include "src/core/lib/slice/slice_string_helpers.h" +#include "src/core/lib/surface/call.h" +#include "src/core/lib/surface/channel.h" +#include "src/core/lib/surface/channel_init.h" +#include "src/core/lib/transport/static_metadata.h" + +#define GRPC_XDS_INITIAL_CONNECT_BACKOFF_SECONDS 1 +#define GRPC_XDS_RECONNECT_BACKOFF_MULTIPLIER 1.6 +#define GRPC_XDS_RECONNECT_MAX_BACKOFF_SECONDS 120 +#define GRPC_XDS_RECONNECT_JITTER 0.2 +#define GRPC_XDS_DEFAULT_FALLBACK_TIMEOUT_MS 10000 + +namespace grpc_core { + +TraceFlag grpc_lb_xds_trace(false, "xds"); + +namespace { + +class XdsLb : public LoadBalancingPolicy { + public: + XdsLb(const grpc_lb_addresses* addresses, const Args& args); + + void UpdateLocked(const grpc_channel_args& args) override; + bool PickLocked(PickState* pick, grpc_error** error) override; + void CancelPickLocked(PickState* pick, grpc_error* error) override; + void CancelMatchingPicksLocked(uint32_t initial_metadata_flags_mask, + uint32_t initial_metadata_flags_eq, + grpc_error* error) override; + void NotifyOnStateChangeLocked(grpc_connectivity_state* state, + grpc_closure* closure) override; + grpc_connectivity_state CheckConnectivityLocked( + grpc_error** connectivity_error) override; + void HandOffPendingPicksLocked(LoadBalancingPolicy* new_policy) override; + void ExitIdleLocked() override; + void ResetBackoffLocked() override; + void FillChildRefsForChannelz( + channelz::ChildRefsList* child_subchannels, + channelz::ChildRefsList* child_channels) override; + + private: + /// Linked list of pending pick requests. It stores all information needed to + /// eventually call (Round Robin's) pick() on them. They mainly stay pending + /// waiting for the RR policy to be created. + /// + /// Note that when a pick is sent to the RR policy, we inject our own + /// on_complete callback, so that we can intercept the result before + /// invoking the original on_complete callback. This allows us to set the + /// LB token metadata and add client_stats to the call context. + /// See \a pending_pick_complete() for details. + struct PendingPick { + // The xds lb instance that created the wrapping. This instance is not + // owned; reference counts are untouched. It's used only for logging + // purposes. + XdsLb* xdslb_policy; + // The original pick. + PickState* pick; + // Our on_complete closure and the original one. + grpc_closure on_complete; + grpc_closure* original_on_complete; + // The LB token associated with the pick. This is set via user_data in + // the pick. + grpc_mdelem lb_token; + // Stats for client-side load reporting. + RefCountedPtr<XdsLbClientStats> client_stats; + // Next pending pick. + PendingPick* next = nullptr; + }; + + /// Contains a call to the LB server and all the data related to the call. + class BalancerCallState + : public InternallyRefCountedWithTracing<BalancerCallState> { + public: + explicit BalancerCallState( + RefCountedPtr<LoadBalancingPolicy> parent_xdslb_policy); + + // It's the caller's responsibility to ensure that Orphan() is called from + // inside the combiner. + void Orphan() override; + + void StartQuery(); + + XdsLbClientStats* client_stats() const { return client_stats_.get(); } + + bool seen_initial_response() const { return seen_initial_response_; } + + private: + // So Delete() can access our private dtor. + template <typename T> + friend void grpc_core::Delete(T*); + + ~BalancerCallState(); + + XdsLb* xdslb_policy() const { + return static_cast<XdsLb*>(xdslb_policy_.get()); + } + + void ScheduleNextClientLoadReportLocked(); + void SendClientLoadReportLocked(); + + static bool LoadReportCountersAreZero(xds_grpclb_request* request); + + static void MaybeSendClientLoadReportLocked(void* arg, grpc_error* error); + static void ClientLoadReportDoneLocked(void* arg, grpc_error* error); + static void OnInitialRequestSentLocked(void* arg, grpc_error* error); + static void OnBalancerMessageReceivedLocked(void* arg, grpc_error* error); + static void OnBalancerStatusReceivedLocked(void* arg, grpc_error* error); + + // The owning LB policy. + RefCountedPtr<LoadBalancingPolicy> xdslb_policy_; + + // The streaming call to the LB server. Always non-NULL. + grpc_call* lb_call_ = nullptr; + + // recv_initial_metadata + grpc_metadata_array lb_initial_metadata_recv_; + + // send_message + grpc_byte_buffer* send_message_payload_ = nullptr; + grpc_closure lb_on_initial_request_sent_; + + // recv_message + grpc_byte_buffer* recv_message_payload_ = nullptr; + grpc_closure lb_on_balancer_message_received_; + bool seen_initial_response_ = false; + + // recv_trailing_metadata + grpc_closure lb_on_balancer_status_received_; + grpc_metadata_array lb_trailing_metadata_recv_; + grpc_status_code lb_call_status_; + grpc_slice lb_call_status_details_; + + // The stats for client-side load reporting associated with this LB call. + // Created after the first serverlist is received. + RefCountedPtr<XdsLbClientStats> client_stats_; + grpc_millis client_stats_report_interval_ = 0; + grpc_timer client_load_report_timer_; + bool client_load_report_timer_callback_pending_ = false; + bool last_client_load_report_counters_were_zero_ = false; + bool client_load_report_is_due_ = false; + // The closure used for either the load report timer or the callback for + // completion of sending the load report. + grpc_closure client_load_report_closure_; + }; + + ~XdsLb(); + + void ShutdownLocked() override; + + // Helper function used in ctor and UpdateLocked(). + void ProcessChannelArgsLocked(const grpc_channel_args& args); + + // Methods for dealing with the balancer channel and call. + void StartPickingLocked(); + void StartBalancerCallLocked(); + static void OnFallbackTimerLocked(void* arg, grpc_error* error); + void StartBalancerCallRetryTimerLocked(); + static void OnBalancerCallRetryTimerLocked(void* arg, grpc_error* error); + static void OnBalancerChannelConnectivityChangedLocked(void* arg, + grpc_error* error); + + // Pending pick methods. + static void PendingPickSetMetadataAndContext(PendingPick* pp); + PendingPick* PendingPickCreate(PickState* pick); + void AddPendingPick(PendingPick* pp); + static void OnPendingPickComplete(void* arg, grpc_error* error); + + // Methods for dealing with the RR policy. + void CreateOrUpdateRoundRobinPolicyLocked(); + grpc_channel_args* CreateRoundRobinPolicyArgsLocked(); + void CreateRoundRobinPolicyLocked(const Args& args); + bool PickFromRoundRobinPolicyLocked(bool force_async, PendingPick* pp, + grpc_error** error); + void UpdateConnectivityStateFromRoundRobinPolicyLocked( + grpc_error* rr_state_error); + static void OnRoundRobinConnectivityChangedLocked(void* arg, + grpc_error* error); + static void OnRoundRobinRequestReresolutionLocked(void* arg, + grpc_error* error); + + // Who the client is trying to communicate with. + const char* server_name_ = nullptr; + + // Current channel args from the resolver. + grpc_channel_args* args_ = nullptr; + + // Internal state. + bool started_picking_ = false; + bool shutting_down_ = false; + grpc_connectivity_state_tracker state_tracker_; + + // The channel for communicating with the LB server. + grpc_channel* lb_channel_ = nullptr; + // Mutex to protect the channel to the LB server. This is used when + // processing a channelz request. + gpr_mu lb_channel_mu_; + grpc_connectivity_state lb_channel_connectivity_; + grpc_closure lb_channel_on_connectivity_changed_; + // Are we already watching the LB channel's connectivity? + bool watching_lb_channel_ = false; + // Response generator to inject address updates into lb_channel_. + RefCountedPtr<FakeResolverResponseGenerator> response_generator_; + + // The data associated with the current LB call. It holds a ref to this LB + // policy. It's initialized every time we query for backends. It's reset to + // NULL whenever the current LB call is no longer needed (e.g., the LB policy + // is shutting down, or the LB call has ended). A non-NULL lb_calld_ always + // contains a non-NULL lb_call_. + OrphanablePtr<BalancerCallState> lb_calld_; + // Timeout in milliseconds for the LB call. 0 means no deadline. + int lb_call_timeout_ms_ = 0; + // Balancer call retry state. + BackOff lb_call_backoff_; + bool retry_timer_callback_pending_ = false; + grpc_timer lb_call_retry_timer_; + grpc_closure lb_on_call_retry_; + + // The deserialized response from the balancer. May be nullptr until one + // such response has arrived. + xds_grpclb_serverlist* serverlist_ = nullptr; + // Index into serverlist for next pick. + // If the server at this index is a drop, we return a drop. + // Otherwise, we delegate to the RR policy. + size_t serverlist_index_ = 0; + + // Timeout in milliseconds for before using fallback backend addresses. + // 0 means not using fallback. + int lb_fallback_timeout_ms_ = 0; + // The backend addresses from the resolver. + grpc_lb_addresses* fallback_backend_addresses_ = nullptr; + // Fallback timer. + bool fallback_timer_callback_pending_ = false; + grpc_timer lb_fallback_timer_; + grpc_closure lb_on_fallback_; + + // Pending picks that are waiting on the RR policy's connectivity. + PendingPick* pending_picks_ = nullptr; + + // The RR policy to use for the backends. + OrphanablePtr<LoadBalancingPolicy> rr_policy_; + grpc_connectivity_state rr_connectivity_state_; + grpc_closure on_rr_connectivity_changed_; + grpc_closure on_rr_request_reresolution_; +}; + +// +// serverlist parsing code +// + +// vtable for LB tokens in grpc_lb_addresses +void* lb_token_copy(void* token) { + return token == nullptr + ? nullptr + : (void*)GRPC_MDELEM_REF(grpc_mdelem{(uintptr_t)token}).payload; +} +void lb_token_destroy(void* token) { + if (token != nullptr) { + GRPC_MDELEM_UNREF(grpc_mdelem{(uintptr_t)token}); + } +} +int lb_token_cmp(void* token1, void* token2) { + if (token1 > token2) return 1; + if (token1 < token2) return -1; + return 0; +} +const grpc_lb_user_data_vtable lb_token_vtable = { + lb_token_copy, lb_token_destroy, lb_token_cmp}; + +// Returns the backend addresses extracted from the given addresses. +grpc_lb_addresses* ExtractBackendAddresses(const grpc_lb_addresses* addresses) { + // First pass: count the number of backend addresses. + size_t num_backends = 0; + for (size_t i = 0; i < addresses->num_addresses; ++i) { + if (!addresses->addresses[i].is_balancer) { + ++num_backends; + } + } + // Second pass: actually populate the addresses and (empty) LB tokens. + grpc_lb_addresses* backend_addresses = + grpc_lb_addresses_create(num_backends, &lb_token_vtable); + size_t num_copied = 0; + for (size_t i = 0; i < addresses->num_addresses; ++i) { + if (addresses->addresses[i].is_balancer) continue; + const grpc_resolved_address* addr = &addresses->addresses[i].address; + grpc_lb_addresses_set_address(backend_addresses, num_copied, &addr->addr, + addr->len, false /* is_balancer */, + nullptr /* balancer_name */, + (void*)GRPC_MDELEM_LB_TOKEN_EMPTY.payload); + ++num_copied; + } + return backend_addresses; +} + +bool IsServerValid(const xds_grpclb_server* server, size_t idx, bool log) { + if (server->drop) return false; + const xds_grpclb_ip_address* ip = &server->ip_address; + if (GPR_UNLIKELY(server->port >> 16 != 0)) { + if (log) { + gpr_log(GPR_ERROR, + "Invalid port '%d' at index %lu of serverlist. Ignoring.", + server->port, (unsigned long)idx); + } + return false; + } + if (GPR_UNLIKELY(ip->size != 4 && ip->size != 16)) { + if (log) { + gpr_log(GPR_ERROR, + "Expected IP to be 4 or 16 bytes, got %d at index %lu of " + "serverlist. Ignoring", + ip->size, (unsigned long)idx); + } + return false; + } + return true; +} + +void ParseServer(const xds_grpclb_server* server, grpc_resolved_address* addr) { + memset(addr, 0, sizeof(*addr)); + if (server->drop) return; + const uint16_t netorder_port = grpc_htons((uint16_t)server->port); + /* the addresses are given in binary format (a in(6)_addr struct) in + * server->ip_address.bytes. */ + const xds_grpclb_ip_address* ip = &server->ip_address; + if (ip->size == 4) { + addr->len = static_cast<socklen_t>(sizeof(grpc_sockaddr_in)); + grpc_sockaddr_in* addr4 = reinterpret_cast<grpc_sockaddr_in*>(&addr->addr); + addr4->sin_family = GRPC_AF_INET; + memcpy(&addr4->sin_addr, ip->bytes, ip->size); + addr4->sin_port = netorder_port; + } else if (ip->size == 16) { + addr->len = static_cast<socklen_t>(sizeof(grpc_sockaddr_in6)); + grpc_sockaddr_in6* addr6 = (grpc_sockaddr_in6*)&addr->addr; + addr6->sin6_family = GRPC_AF_INET6; + memcpy(&addr6->sin6_addr, ip->bytes, ip->size); + addr6->sin6_port = netorder_port; + } +} + +// Returns addresses extracted from \a serverlist. +grpc_lb_addresses* ProcessServerlist(const xds_grpclb_serverlist* serverlist) { + size_t num_valid = 0; + /* first pass: count how many are valid in order to allocate the necessary + * memory in a single block */ + for (size_t i = 0; i < serverlist->num_servers; ++i) { + if (IsServerValid(serverlist->servers[i], i, true)) ++num_valid; + } + grpc_lb_addresses* lb_addresses = + grpc_lb_addresses_create(num_valid, &lb_token_vtable); + /* second pass: actually populate the addresses and LB tokens (aka user data + * to the outside world) to be read by the RR policy during its creation. + * Given that the validity tests are very cheap, they are performed again + * instead of marking the valid ones during the first pass, as this would + * incurr in an allocation due to the arbitrary number of server */ + size_t addr_idx = 0; + for (size_t sl_idx = 0; sl_idx < serverlist->num_servers; ++sl_idx) { + const xds_grpclb_server* server = serverlist->servers[sl_idx]; + if (!IsServerValid(serverlist->servers[sl_idx], sl_idx, false)) continue; + GPR_ASSERT(addr_idx < num_valid); + /* address processing */ + grpc_resolved_address addr; + ParseServer(server, &addr); + /* lb token processing */ + void* user_data; + if (server->has_load_balance_token) { + const size_t lb_token_max_length = + GPR_ARRAY_SIZE(server->load_balance_token); + const size_t lb_token_length = + strnlen(server->load_balance_token, lb_token_max_length); + grpc_slice lb_token_mdstr = grpc_slice_from_copied_buffer( + server->load_balance_token, lb_token_length); + user_data = + (void*)grpc_mdelem_from_slices(GRPC_MDSTR_LB_TOKEN, lb_token_mdstr) + .payload; + } else { + char* uri = grpc_sockaddr_to_uri(&addr); + gpr_log(GPR_INFO, + "Missing LB token for backend address '%s'. The empty token will " + "be used instead", + uri); + gpr_free(uri); + user_data = (void*)GRPC_MDELEM_LB_TOKEN_EMPTY.payload; + } + grpc_lb_addresses_set_address(lb_addresses, addr_idx, &addr.addr, addr.len, + false /* is_balancer */, + nullptr /* balancer_name */, user_data); + ++addr_idx; + } + GPR_ASSERT(addr_idx == num_valid); + return lb_addresses; +} + +// +// XdsLb::BalancerCallState +// + +XdsLb::BalancerCallState::BalancerCallState( + RefCountedPtr<LoadBalancingPolicy> parent_xdslb_policy) + : InternallyRefCountedWithTracing<BalancerCallState>(&grpc_lb_xds_trace), + xdslb_policy_(std::move(parent_xdslb_policy)) { + GPR_ASSERT(xdslb_policy_ != nullptr); + GPR_ASSERT(!xdslb_policy()->shutting_down_); + // Init the LB call. Note that the LB call will progress every time there's + // activity in xdslb_policy_->interested_parties(), which is comprised of + // the polling entities from client_channel. + GPR_ASSERT(xdslb_policy()->server_name_ != nullptr); + GPR_ASSERT(xdslb_policy()->server_name_[0] != '\0'); + const grpc_millis deadline = + xdslb_policy()->lb_call_timeout_ms_ == 0 + ? GRPC_MILLIS_INF_FUTURE + : ExecCtx::Get()->Now() + xdslb_policy()->lb_call_timeout_ms_; + lb_call_ = grpc_channel_create_pollset_set_call( + xdslb_policy()->lb_channel_, nullptr, GRPC_PROPAGATE_DEFAULTS, + xdslb_policy_->interested_parties(), + GRPC_MDSTR_SLASH_GRPC_DOT_LB_DOT_V1_DOT_LOADBALANCER_SLASH_BALANCELOAD, + nullptr, deadline, nullptr); + // Init the LB call request payload. + xds_grpclb_request* request = + xds_grpclb_request_create(xdslb_policy()->server_name_); + grpc_slice request_payload_slice = xds_grpclb_request_encode(request); + send_message_payload_ = + grpc_raw_byte_buffer_create(&request_payload_slice, 1); + grpc_slice_unref_internal(request_payload_slice); + xds_grpclb_request_destroy(request); + // Init other data associated with the LB call. + grpc_metadata_array_init(&lb_initial_metadata_recv_); + grpc_metadata_array_init(&lb_trailing_metadata_recv_); + GRPC_CLOSURE_INIT(&lb_on_initial_request_sent_, OnInitialRequestSentLocked, + this, grpc_combiner_scheduler(xdslb_policy()->combiner())); + GRPC_CLOSURE_INIT(&lb_on_balancer_message_received_, + OnBalancerMessageReceivedLocked, this, + grpc_combiner_scheduler(xdslb_policy()->combiner())); + GRPC_CLOSURE_INIT(&lb_on_balancer_status_received_, + OnBalancerStatusReceivedLocked, this, + grpc_combiner_scheduler(xdslb_policy()->combiner())); +} + +XdsLb::BalancerCallState::~BalancerCallState() { + GPR_ASSERT(lb_call_ != nullptr); + grpc_call_unref(lb_call_); + grpc_metadata_array_destroy(&lb_initial_metadata_recv_); + grpc_metadata_array_destroy(&lb_trailing_metadata_recv_); + grpc_byte_buffer_destroy(send_message_payload_); + grpc_byte_buffer_destroy(recv_message_payload_); + grpc_slice_unref_internal(lb_call_status_details_); +} + +void XdsLb::BalancerCallState::Orphan() { + GPR_ASSERT(lb_call_ != nullptr); + // If we are here because xdslb_policy wants to cancel the call, + // lb_on_balancer_status_received_ will complete the cancellation and clean + // up. Otherwise, we are here because xdslb_policy has to orphan a failed + // call, then the following cancellation will be a no-op. + grpc_call_cancel(lb_call_, nullptr); + if (client_load_report_timer_callback_pending_) { + grpc_timer_cancel(&client_load_report_timer_); + } + // Note that the initial ref is hold by lb_on_balancer_status_received_ + // instead of the caller of this function. So the corresponding unref happens + // in lb_on_balancer_status_received_ instead of here. +} + +void XdsLb::BalancerCallState::StartQuery() { + GPR_ASSERT(lb_call_ != nullptr); + if (grpc_lb_xds_trace.enabled()) { + gpr_log(GPR_INFO, "[xdslb %p] Starting LB call (lb_calld: %p, lb_call: %p)", + xdslb_policy_.get(), this, lb_call_); + } + // Create the ops. + grpc_call_error call_error; + grpc_op ops[3]; + memset(ops, 0, sizeof(ops)); + // Op: send initial metadata. + grpc_op* op = ops; + op->op = GRPC_OP_SEND_INITIAL_METADATA; + op->data.send_initial_metadata.count = 0; + op->flags = 0; + op->reserved = nullptr; + op++; + // Op: send request message. + GPR_ASSERT(send_message_payload_ != nullptr); + op->op = GRPC_OP_SEND_MESSAGE; + op->data.send_message.send_message = send_message_payload_; + op->flags = 0; + op->reserved = nullptr; + op++; + // TODO(roth): We currently track this ref manually. Once the + // ClosureRef API is ready, we should pass the RefCountedPtr<> along + // with the callback. + auto self = Ref(DEBUG_LOCATION, "on_initial_request_sent"); + self.release(); + call_error = grpc_call_start_batch_and_execute( + lb_call_, ops, (size_t)(op - ops), &lb_on_initial_request_sent_); + GPR_ASSERT(GRPC_CALL_OK == call_error); + // Op: recv initial metadata. + op = ops; + op->op = GRPC_OP_RECV_INITIAL_METADATA; + op->data.recv_initial_metadata.recv_initial_metadata = + &lb_initial_metadata_recv_; + op->flags = 0; + op->reserved = nullptr; + op++; + // Op: recv response. + op->op = GRPC_OP_RECV_MESSAGE; + op->data.recv_message.recv_message = &recv_message_payload_; + op->flags = 0; + op->reserved = nullptr; + op++; + // TODO(roth): We currently track this ref manually. Once the + // ClosureRef API is ready, we should pass the RefCountedPtr<> along + // with the callback. + self = Ref(DEBUG_LOCATION, "on_message_received"); + self.release(); + call_error = grpc_call_start_batch_and_execute( + lb_call_, ops, (size_t)(op - ops), &lb_on_balancer_message_received_); + GPR_ASSERT(GRPC_CALL_OK == call_error); + // Op: recv server status. + op = ops; + op->op = GRPC_OP_RECV_STATUS_ON_CLIENT; + op->data.recv_status_on_client.trailing_metadata = + &lb_trailing_metadata_recv_; + op->data.recv_status_on_client.status = &lb_call_status_; + op->data.recv_status_on_client.status_details = &lb_call_status_details_; + op->flags = 0; + op->reserved = nullptr; + op++; + // This callback signals the end of the LB call, so it relies on the initial + // ref instead of a new ref. When it's invoked, it's the initial ref that is + // unreffed. + call_error = grpc_call_start_batch_and_execute( + lb_call_, ops, (size_t)(op - ops), &lb_on_balancer_status_received_); + GPR_ASSERT(GRPC_CALL_OK == call_error); +} + +void XdsLb::BalancerCallState::ScheduleNextClientLoadReportLocked() { + const grpc_millis next_client_load_report_time = + ExecCtx::Get()->Now() + client_stats_report_interval_; + GRPC_CLOSURE_INIT(&client_load_report_closure_, + MaybeSendClientLoadReportLocked, this, + grpc_combiner_scheduler(xdslb_policy()->combiner())); + grpc_timer_init(&client_load_report_timer_, next_client_load_report_time, + &client_load_report_closure_); + client_load_report_timer_callback_pending_ = true; +} + +void XdsLb::BalancerCallState::MaybeSendClientLoadReportLocked( + void* arg, grpc_error* error) { + BalancerCallState* lb_calld = static_cast<BalancerCallState*>(arg); + XdsLb* xdslb_policy = lb_calld->xdslb_policy(); + lb_calld->client_load_report_timer_callback_pending_ = false; + if (error != GRPC_ERROR_NONE || lb_calld != xdslb_policy->lb_calld_.get()) { + lb_calld->Unref(DEBUG_LOCATION, "client_load_report"); + return; + } + // If we've already sent the initial request, then we can go ahead and send + // the load report. Otherwise, we need to wait until the initial request has + // been sent to send this (see OnInitialRequestSentLocked()). + if (lb_calld->send_message_payload_ == nullptr) { + lb_calld->SendClientLoadReportLocked(); + } else { + lb_calld->client_load_report_is_due_ = true; + } +} + +bool XdsLb::BalancerCallState::LoadReportCountersAreZero( + xds_grpclb_request* request) { + XdsLbClientStats::DroppedCallCounts* drop_entries = + static_cast<XdsLbClientStats::DroppedCallCounts*>( + request->client_stats.calls_finished_with_drop.arg); + return request->client_stats.num_calls_started == 0 && + request->client_stats.num_calls_finished == 0 && + request->client_stats.num_calls_finished_with_client_failed_to_send == + 0 && + request->client_stats.num_calls_finished_known_received == 0 && + (drop_entries == nullptr || drop_entries->size() == 0); +} + +void XdsLb::BalancerCallState::SendClientLoadReportLocked() { + // Construct message payload. + GPR_ASSERT(send_message_payload_ == nullptr); + xds_grpclb_request* request = + xds_grpclb_load_report_request_create_locked(client_stats_.get()); + // Skip client load report if the counters were all zero in the last + // report and they are still zero in this one. + if (LoadReportCountersAreZero(request)) { + if (last_client_load_report_counters_were_zero_) { + xds_grpclb_request_destroy(request); + ScheduleNextClientLoadReportLocked(); + return; + } + last_client_load_report_counters_were_zero_ = true; + } else { + last_client_load_report_counters_were_zero_ = false; + } + grpc_slice request_payload_slice = xds_grpclb_request_encode(request); + send_message_payload_ = + grpc_raw_byte_buffer_create(&request_payload_slice, 1); + grpc_slice_unref_internal(request_payload_slice); + xds_grpclb_request_destroy(request); + // Send the report. + grpc_op op; + memset(&op, 0, sizeof(op)); + op.op = GRPC_OP_SEND_MESSAGE; + op.data.send_message.send_message = send_message_payload_; + GRPC_CLOSURE_INIT(&client_load_report_closure_, ClientLoadReportDoneLocked, + this, grpc_combiner_scheduler(xdslb_policy()->combiner())); + grpc_call_error call_error = grpc_call_start_batch_and_execute( + lb_call_, &op, 1, &client_load_report_closure_); + if (GPR_UNLIKELY(call_error != GRPC_CALL_OK)) { + gpr_log(GPR_ERROR, "[xdslb %p] call_error=%d", xdslb_policy_.get(), + call_error); + GPR_ASSERT(GRPC_CALL_OK == call_error); + } +} + +void XdsLb::BalancerCallState::ClientLoadReportDoneLocked(void* arg, + grpc_error* error) { + BalancerCallState* lb_calld = static_cast<BalancerCallState*>(arg); + XdsLb* xdslb_policy = lb_calld->xdslb_policy(); + grpc_byte_buffer_destroy(lb_calld->send_message_payload_); + lb_calld->send_message_payload_ = nullptr; + if (error != GRPC_ERROR_NONE || lb_calld != xdslb_policy->lb_calld_.get()) { + lb_calld->Unref(DEBUG_LOCATION, "client_load_report"); + return; + } + lb_calld->ScheduleNextClientLoadReportLocked(); +} + +void XdsLb::BalancerCallState::OnInitialRequestSentLocked(void* arg, + grpc_error* error) { + BalancerCallState* lb_calld = static_cast<BalancerCallState*>(arg); + grpc_byte_buffer_destroy(lb_calld->send_message_payload_); + lb_calld->send_message_payload_ = nullptr; + // If we attempted to send a client load report before the initial request was + // sent (and this lb_calld is still in use), send the load report now. + if (lb_calld->client_load_report_is_due_ && + lb_calld == lb_calld->xdslb_policy()->lb_calld_.get()) { + lb_calld->SendClientLoadReportLocked(); + lb_calld->client_load_report_is_due_ = false; + } + lb_calld->Unref(DEBUG_LOCATION, "on_initial_request_sent"); +} + +void XdsLb::BalancerCallState::OnBalancerMessageReceivedLocked( + void* arg, grpc_error* error) { + BalancerCallState* lb_calld = static_cast<BalancerCallState*>(arg); + XdsLb* xdslb_policy = lb_calld->xdslb_policy(); + // Empty payload means the LB call was cancelled. + if (lb_calld != xdslb_policy->lb_calld_.get() || + lb_calld->recv_message_payload_ == nullptr) { + lb_calld->Unref(DEBUG_LOCATION, "on_message_received"); + return; + } + grpc_byte_buffer_reader bbr; + grpc_byte_buffer_reader_init(&bbr, lb_calld->recv_message_payload_); + grpc_slice response_slice = grpc_byte_buffer_reader_readall(&bbr); + grpc_byte_buffer_reader_destroy(&bbr); + grpc_byte_buffer_destroy(lb_calld->recv_message_payload_); + lb_calld->recv_message_payload_ = nullptr; + xds_grpclb_initial_response* initial_response; + xds_grpclb_serverlist* serverlist; + if (!lb_calld->seen_initial_response_ && + (initial_response = xds_grpclb_initial_response_parse(response_slice)) != + nullptr) { + // Have NOT seen initial response, look for initial response. + if (initial_response->has_client_stats_report_interval) { + lb_calld->client_stats_report_interval_ = GPR_MAX( + GPR_MS_PER_SEC, xds_grpclb_duration_to_millis( + &initial_response->client_stats_report_interval)); + if (grpc_lb_xds_trace.enabled()) { + gpr_log(GPR_INFO, + "[xdslb %p] Received initial LB response message; " + "client load reporting interval = %" PRId64 " milliseconds", + xdslb_policy, lb_calld->client_stats_report_interval_); + } + } else if (grpc_lb_xds_trace.enabled()) { + gpr_log(GPR_INFO, + "[xdslb %p] Received initial LB response message; client load " + "reporting NOT enabled", + xdslb_policy); + } + xds_grpclb_initial_response_destroy(initial_response); + lb_calld->seen_initial_response_ = true; + } else if ((serverlist = xds_grpclb_response_parse_serverlist( + response_slice)) != nullptr) { + // Have seen initial response, look for serverlist. + GPR_ASSERT(lb_calld->lb_call_ != nullptr); + if (grpc_lb_xds_trace.enabled()) { + gpr_log(GPR_INFO, + "[xdslb %p] Serverlist with %" PRIuPTR " servers received", + xdslb_policy, serverlist->num_servers); + for (size_t i = 0; i < serverlist->num_servers; ++i) { + grpc_resolved_address addr; + ParseServer(serverlist->servers[i], &addr); + char* ipport; + grpc_sockaddr_to_string(&ipport, &addr, false); + gpr_log(GPR_INFO, "[xdslb %p] Serverlist[%" PRIuPTR "]: %s", + xdslb_policy, i, ipport); + gpr_free(ipport); + } + } + /* update serverlist */ + if (serverlist->num_servers > 0) { + // Start sending client load report only after we start using the + // serverlist returned from the current LB call. + if (lb_calld->client_stats_report_interval_ > 0 && + lb_calld->client_stats_ == nullptr) { + lb_calld->client_stats_.reset(New<XdsLbClientStats>()); + // TODO(roth): We currently track this ref manually. Once the + // ClosureRef API is ready, we should pass the RefCountedPtr<> along + // with the callback. + auto self = lb_calld->Ref(DEBUG_LOCATION, "client_load_report"); + self.release(); + lb_calld->ScheduleNextClientLoadReportLocked(); + } + if (xds_grpclb_serverlist_equals(xdslb_policy->serverlist_, serverlist)) { + if (grpc_lb_xds_trace.enabled()) { + gpr_log(GPR_INFO, + "[xdslb %p] Incoming server list identical to current, " + "ignoring.", + xdslb_policy); + } + xds_grpclb_destroy_serverlist(serverlist); + } else { /* new serverlist */ + if (xdslb_policy->serverlist_ != nullptr) { + /* dispose of the old serverlist */ + xds_grpclb_destroy_serverlist(xdslb_policy->serverlist_); + } else { + /* or dispose of the fallback */ + grpc_lb_addresses_destroy(xdslb_policy->fallback_backend_addresses_); + xdslb_policy->fallback_backend_addresses_ = nullptr; + if (xdslb_policy->fallback_timer_callback_pending_) { + grpc_timer_cancel(&xdslb_policy->lb_fallback_timer_); + } + } + // and update the copy in the XdsLb instance. This + // serverlist instance will be destroyed either upon the next + // update or when the XdsLb instance is destroyed. + xdslb_policy->serverlist_ = serverlist; + xdslb_policy->serverlist_index_ = 0; + xdslb_policy->CreateOrUpdateRoundRobinPolicyLocked(); + } + } else { + if (grpc_lb_xds_trace.enabled()) { + gpr_log(GPR_INFO, "[xdslb %p] Received empty server list, ignoring.", + xdslb_policy); + } + xds_grpclb_destroy_serverlist(serverlist); + } + } else { + // No valid initial response or serverlist found. + char* response_slice_str = + grpc_dump_slice(response_slice, GPR_DUMP_ASCII | GPR_DUMP_HEX); + gpr_log(GPR_ERROR, + "[xdslb %p] Invalid LB response received: '%s'. Ignoring.", + xdslb_policy, response_slice_str); + gpr_free(response_slice_str); + } + grpc_slice_unref_internal(response_slice); + if (!xdslb_policy->shutting_down_) { + // Keep listening for serverlist updates. + grpc_op op; + memset(&op, 0, sizeof(op)); + op.op = GRPC_OP_RECV_MESSAGE; + op.data.recv_message.recv_message = &lb_calld->recv_message_payload_; + op.flags = 0; + op.reserved = nullptr; + // Reuse the "OnBalancerMessageReceivedLocked" ref taken in StartQuery(). + const grpc_call_error call_error = grpc_call_start_batch_and_execute( + lb_calld->lb_call_, &op, 1, + &lb_calld->lb_on_balancer_message_received_); + GPR_ASSERT(GRPC_CALL_OK == call_error); + } else { + lb_calld->Unref(DEBUG_LOCATION, "on_message_received+grpclb_shutdown"); + } +} + +void XdsLb::BalancerCallState::OnBalancerStatusReceivedLocked( + void* arg, grpc_error* error) { + BalancerCallState* lb_calld = static_cast<BalancerCallState*>(arg); + XdsLb* xdslb_policy = lb_calld->xdslb_policy(); + GPR_ASSERT(lb_calld->lb_call_ != nullptr); + if (grpc_lb_xds_trace.enabled()) { + char* status_details = + grpc_slice_to_c_string(lb_calld->lb_call_status_details_); + gpr_log(GPR_INFO, + "[xdslb %p] Status from LB server received. Status = %d, details " + "= '%s', (lb_calld: %p, lb_call: %p), error '%s'", + xdslb_policy, lb_calld->lb_call_status_, status_details, lb_calld, + lb_calld->lb_call_, grpc_error_string(error)); + gpr_free(status_details); + } + xdslb_policy->TryReresolutionLocked(&grpc_lb_xds_trace, GRPC_ERROR_NONE); + // If this lb_calld is still in use, this call ended because of a failure so + // we want to retry connecting. Otherwise, we have deliberately ended this + // call and no further action is required. + if (lb_calld == xdslb_policy->lb_calld_.get()) { + xdslb_policy->lb_calld_.reset(); + GPR_ASSERT(!xdslb_policy->shutting_down_); + if (lb_calld->seen_initial_response_) { + // If we lose connection to the LB server, reset the backoff and restart + // the LB call immediately. + xdslb_policy->lb_call_backoff_.Reset(); + xdslb_policy->StartBalancerCallLocked(); + } else { + // If this LB call fails establishing any connection to the LB server, + // retry later. + xdslb_policy->StartBalancerCallRetryTimerLocked(); + } + } + lb_calld->Unref(DEBUG_LOCATION, "lb_call_ended"); +} + +// +// helper code for creating balancer channel +// + +grpc_lb_addresses* ExtractBalancerAddresses( + const grpc_lb_addresses* addresses) { + size_t num_grpclb_addrs = 0; + for (size_t i = 0; i < addresses->num_addresses; ++i) { + if (addresses->addresses[i].is_balancer) ++num_grpclb_addrs; + } + // There must be at least one balancer address, or else the + // client_channel would not have chosen this LB policy. + GPR_ASSERT(num_grpclb_addrs > 0); + grpc_lb_addresses* lb_addresses = + grpc_lb_addresses_create(num_grpclb_addrs, nullptr); + size_t lb_addresses_idx = 0; + for (size_t i = 0; i < addresses->num_addresses; ++i) { + if (!addresses->addresses[i].is_balancer) continue; + if (GPR_UNLIKELY(addresses->addresses[i].user_data != nullptr)) { + gpr_log(GPR_ERROR, + "This LB policy doesn't support user data. It will be ignored"); + } + grpc_lb_addresses_set_address( + lb_addresses, lb_addresses_idx++, addresses->addresses[i].address.addr, + addresses->addresses[i].address.len, false /* is balancer */, + addresses->addresses[i].balancer_name, nullptr /* user data */); + } + GPR_ASSERT(num_grpclb_addrs == lb_addresses_idx); + return lb_addresses; +} + +/* Returns the channel args for the LB channel, used to create a bidirectional + * stream for the reception of load balancing updates. + * + * Inputs: + * - \a addresses: corresponding to the balancers. + * - \a response_generator: in order to propagate updates from the resolver + * above the grpclb policy. + * - \a args: other args inherited from the grpclb policy. */ +grpc_channel_args* BuildBalancerChannelArgs( + const grpc_lb_addresses* addresses, + FakeResolverResponseGenerator* response_generator, + const grpc_channel_args* args) { + grpc_lb_addresses* lb_addresses = ExtractBalancerAddresses(addresses); + // Channel args to remove. + static const char* args_to_remove[] = { + // LB policy name, since we want to use the default (pick_first) in + // the LB channel. + GRPC_ARG_LB_POLICY_NAME, + // The channel arg for the server URI, since that will be different for + // the LB channel than for the parent channel. The client channel + // factory will re-add this arg with the right value. + GRPC_ARG_SERVER_URI, + // The resolved addresses, which will be generated by the name resolver + // used in the LB channel. Note that the LB channel will use the fake + // resolver, so this won't actually generate a query to DNS (or some + // other name service). However, the addresses returned by the fake + // resolver will have is_balancer=false, whereas our own addresses have + // is_balancer=true. We need the LB channel to return addresses with + // is_balancer=false so that it does not wind up recursively using the + // grpclb LB policy, as per the special case logic in client_channel.c. + GRPC_ARG_LB_ADDRESSES, + // The fake resolver response generator, because we are replacing it + // with the one from the grpclb policy, used to propagate updates to + // the LB channel. + GRPC_ARG_FAKE_RESOLVER_RESPONSE_GENERATOR, + // The LB channel should use the authority indicated by the target + // authority table (see \a grpc_lb_policy_xds_modify_lb_channel_args), + // as opposed to the authority from the parent channel. + GRPC_ARG_DEFAULT_AUTHORITY, + // Just as for \a GRPC_ARG_DEFAULT_AUTHORITY, the LB channel should be + // treated as a stand-alone channel and not inherit this argument from the + // args of the parent channel. + GRPC_SSL_TARGET_NAME_OVERRIDE_ARG, + }; + // Channel args to add. + const grpc_arg args_to_add[] = { + // New LB addresses. + // Note that we pass these in both when creating the LB channel + // and via the fake resolver. The latter is what actually gets used. + grpc_lb_addresses_create_channel_arg(lb_addresses), + // The fake resolver response generator, which we use to inject + // address updates into the LB channel. + grpc_core::FakeResolverResponseGenerator::MakeChannelArg( + response_generator), + // A channel arg indicating the target is a grpclb load balancer. + grpc_channel_arg_integer_create( + const_cast<char*>(GRPC_ARG_ADDRESS_IS_XDS_LOAD_BALANCER), 1), + // A channel arg indicating this is an internal channels, aka it is + // owned by components in Core, not by the user application. + grpc_channel_arg_integer_create( + const_cast<char*>(GRPC_ARG_CHANNELZ_CHANNEL_IS_INTERNAL_CHANNEL), 1), + }; + // Construct channel args. + grpc_channel_args* new_args = grpc_channel_args_copy_and_add_and_remove( + args, args_to_remove, GPR_ARRAY_SIZE(args_to_remove), args_to_add, + GPR_ARRAY_SIZE(args_to_add)); + // Make any necessary modifications for security. + new_args = grpc_lb_policy_xds_modify_lb_channel_args(new_args); + // Clean up. + grpc_lb_addresses_destroy(lb_addresses); + return new_args; +} + +// +// ctor and dtor +// + +XdsLb::XdsLb(const grpc_lb_addresses* addresses, + const LoadBalancingPolicy::Args& args) + : LoadBalancingPolicy(args), + response_generator_(MakeRefCounted<FakeResolverResponseGenerator>()), + lb_call_backoff_( + BackOff::Options() + .set_initial_backoff(GRPC_XDS_INITIAL_CONNECT_BACKOFF_SECONDS * + 1000) + .set_multiplier(GRPC_XDS_RECONNECT_BACKOFF_MULTIPLIER) + .set_jitter(GRPC_XDS_RECONNECT_JITTER) + .set_max_backoff(GRPC_XDS_RECONNECT_MAX_BACKOFF_SECONDS * 1000)) { + // Initialization. + gpr_mu_init(&lb_channel_mu_); + grpc_subchannel_index_ref(); + GRPC_CLOSURE_INIT(&lb_channel_on_connectivity_changed_, + &XdsLb::OnBalancerChannelConnectivityChangedLocked, this, + grpc_combiner_scheduler(args.combiner)); + GRPC_CLOSURE_INIT(&on_rr_connectivity_changed_, + &XdsLb::OnRoundRobinConnectivityChangedLocked, this, + grpc_combiner_scheduler(args.combiner)); + GRPC_CLOSURE_INIT(&on_rr_request_reresolution_, + &XdsLb::OnRoundRobinRequestReresolutionLocked, this, + grpc_combiner_scheduler(args.combiner)); + grpc_connectivity_state_init(&state_tracker_, GRPC_CHANNEL_IDLE, "xds"); + // Record server name. + const grpc_arg* arg = grpc_channel_args_find(args.args, GRPC_ARG_SERVER_URI); + const char* server_uri = grpc_channel_arg_get_string(arg); + GPR_ASSERT(server_uri != nullptr); + grpc_uri* uri = grpc_uri_parse(server_uri, true); + GPR_ASSERT(uri->path[0] != '\0'); + server_name_ = gpr_strdup(uri->path[0] == '/' ? uri->path + 1 : uri->path); + if (grpc_lb_xds_trace.enabled()) { + gpr_log(GPR_INFO, + "[xdslb %p] Will use '%s' as the server name for LB request.", this, + server_name_); + } + grpc_uri_destroy(uri); + // Record LB call timeout. + arg = grpc_channel_args_find(args.args, GRPC_ARG_GRPCLB_CALL_TIMEOUT_MS); + lb_call_timeout_ms_ = grpc_channel_arg_get_integer(arg, {0, 0, INT_MAX}); + // Record fallback timeout. + arg = grpc_channel_args_find(args.args, GRPC_ARG_GRPCLB_FALLBACK_TIMEOUT_MS); + lb_fallback_timeout_ms_ = grpc_channel_arg_get_integer( + arg, {GRPC_XDS_DEFAULT_FALLBACK_TIMEOUT_MS, 0, INT_MAX}); + // Process channel args. + ProcessChannelArgsLocked(*args.args); +} + +XdsLb::~XdsLb() { + GPR_ASSERT(pending_picks_ == nullptr); + gpr_mu_destroy(&lb_channel_mu_); + gpr_free((void*)server_name_); + grpc_channel_args_destroy(args_); + grpc_connectivity_state_destroy(&state_tracker_); + if (serverlist_ != nullptr) { + xds_grpclb_destroy_serverlist(serverlist_); + } + if (fallback_backend_addresses_ != nullptr) { + grpc_lb_addresses_destroy(fallback_backend_addresses_); + } + grpc_subchannel_index_unref(); +} + +void XdsLb::ShutdownLocked() { + grpc_error* error = GRPC_ERROR_CREATE_FROM_STATIC_STRING("Channel shutdown"); + shutting_down_ = true; + lb_calld_.reset(); + if (retry_timer_callback_pending_) { + grpc_timer_cancel(&lb_call_retry_timer_); + } + if (fallback_timer_callback_pending_) { + grpc_timer_cancel(&lb_fallback_timer_); + } + rr_policy_.reset(); + TryReresolutionLocked(&grpc_lb_xds_trace, GRPC_ERROR_CANCELLED); + // We destroy the LB channel here instead of in our destructor because + // destroying the channel triggers a last callback to + // OnBalancerChannelConnectivityChangedLocked(), and we need to be + // alive when that callback is invoked. + if (lb_channel_ != nullptr) { + gpr_mu_lock(&lb_channel_mu_); + grpc_channel_destroy(lb_channel_); + lb_channel_ = nullptr; + gpr_mu_unlock(&lb_channel_mu_); + } + grpc_connectivity_state_set(&state_tracker_, GRPC_CHANNEL_SHUTDOWN, + GRPC_ERROR_REF(error), "grpclb_shutdown"); + // Clear pending picks. + PendingPick* pp; + while ((pp = pending_picks_) != nullptr) { + pending_picks_ = pp->next; + pp->pick->connected_subchannel.reset(); + // Note: pp is deleted in this callback. + GRPC_CLOSURE_SCHED(&pp->on_complete, GRPC_ERROR_REF(error)); + } + GRPC_ERROR_UNREF(error); +} + +// +// public methods +// + +void XdsLb::HandOffPendingPicksLocked(LoadBalancingPolicy* new_policy) { + PendingPick* pp; + while ((pp = pending_picks_) != nullptr) { + pending_picks_ = pp->next; + pp->pick->on_complete = pp->original_on_complete; + pp->pick->user_data = nullptr; + grpc_error* error = GRPC_ERROR_NONE; + if (new_policy->PickLocked(pp->pick, &error)) { + // Synchronous return; schedule closure. + GRPC_CLOSURE_SCHED(pp->pick->on_complete, error); + } + Delete(pp); + } +} + +// Cancel a specific pending pick. +// +// A grpclb pick progresses as follows: +// - If there's a Round Robin policy (rr_policy_) available, it'll be +// handed over to the RR policy (in CreateRoundRobinPolicyLocked()). From +// that point onwards, it'll be RR's responsibility. For cancellations, that +// implies the pick needs also be cancelled by the RR instance. +// - Otherwise, without an RR instance, picks stay pending at this policy's +// level (grpclb), inside the pending_picks_ list. To cancel these, +// we invoke the completion closure and set the pick's connected +// subchannel to nullptr right here. +void XdsLb::CancelPickLocked(PickState* pick, grpc_error* error) { + PendingPick* pp = pending_picks_; + pending_picks_ = nullptr; + while (pp != nullptr) { + PendingPick* next = pp->next; + if (pp->pick == pick) { + pick->connected_subchannel.reset(); + // Note: pp is deleted in this callback. + GRPC_CLOSURE_SCHED(&pp->on_complete, + GRPC_ERROR_CREATE_REFERENCING_FROM_STATIC_STRING( + "Pick Cancelled", &error, 1)); + } else { + pp->next = pending_picks_; + pending_picks_ = pp; + } + pp = next; + } + if (rr_policy_ != nullptr) { + rr_policy_->CancelPickLocked(pick, GRPC_ERROR_REF(error)); + } + GRPC_ERROR_UNREF(error); +} + +// Cancel all pending picks. +// +// A grpclb pick progresses as follows: +// - If there's a Round Robin policy (rr_policy_) available, it'll be +// handed over to the RR policy (in CreateRoundRobinPolicyLocked()). From +// that point onwards, it'll be RR's responsibility. For cancellations, that +// implies the pick needs also be cancelled by the RR instance. +// - Otherwise, without an RR instance, picks stay pending at this policy's +// level (grpclb), inside the pending_picks_ list. To cancel these, +// we invoke the completion closure and set the pick's connected +// subchannel to nullptr right here. +void XdsLb::CancelMatchingPicksLocked(uint32_t initial_metadata_flags_mask, + uint32_t initial_metadata_flags_eq, + grpc_error* error) { + PendingPick* pp = pending_picks_; + pending_picks_ = nullptr; + while (pp != nullptr) { + PendingPick* next = pp->next; + if ((pp->pick->initial_metadata_flags & initial_metadata_flags_mask) == + initial_metadata_flags_eq) { + // Note: pp is deleted in this callback. + GRPC_CLOSURE_SCHED(&pp->on_complete, + GRPC_ERROR_CREATE_REFERENCING_FROM_STATIC_STRING( + "Pick Cancelled", &error, 1)); + } else { + pp->next = pending_picks_; + pending_picks_ = pp; + } + pp = next; + } + if (rr_policy_ != nullptr) { + rr_policy_->CancelMatchingPicksLocked(initial_metadata_flags_mask, + initial_metadata_flags_eq, + GRPC_ERROR_REF(error)); + } + GRPC_ERROR_UNREF(error); +} + +void XdsLb::ExitIdleLocked() { + if (!started_picking_) { + StartPickingLocked(); + } +} + +void XdsLb::ResetBackoffLocked() { + if (lb_channel_ != nullptr) { + grpc_channel_reset_connect_backoff(lb_channel_); + } + if (rr_policy_ != nullptr) { + rr_policy_->ResetBackoffLocked(); + } +} + +bool XdsLb::PickLocked(PickState* pick, grpc_error** error) { + PendingPick* pp = PendingPickCreate(pick); + bool pick_done = false; + if (rr_policy_ != nullptr) { + if (grpc_lb_xds_trace.enabled()) { + gpr_log(GPR_INFO, "[xdslb %p] about to PICK from RR %p", this, + rr_policy_.get()); + } + pick_done = + PickFromRoundRobinPolicyLocked(false /* force_async */, pp, error); + } else { // rr_policy_ == NULL + if (pick->on_complete == nullptr) { + *error = GRPC_ERROR_CREATE_FROM_STATIC_STRING( + "No pick result available but synchronous result required."); + pick_done = true; + } else { + if (grpc_lb_xds_trace.enabled()) { + gpr_log(GPR_INFO, + "[xdslb %p] No RR policy. Adding to grpclb's pending picks", + this); + } + AddPendingPick(pp); + if (!started_picking_) { + StartPickingLocked(); + } + pick_done = false; + } + } + return pick_done; +} + +void XdsLb::FillChildRefsForChannelz(channelz::ChildRefsList* child_subchannels, + channelz::ChildRefsList* child_channels) { + // delegate to the RoundRobin to fill the children subchannels. + rr_policy_->FillChildRefsForChannelz(child_subchannels, child_channels); + MutexLock lock(&lb_channel_mu_); + if (lb_channel_ != nullptr) { + grpc_core::channelz::ChannelNode* channel_node = + grpc_channel_get_channelz_node(lb_channel_); + if (channel_node != nullptr) { + child_channels->push_back(channel_node->uuid()); + } + } +} + +grpc_connectivity_state XdsLb::CheckConnectivityLocked( + grpc_error** connectivity_error) { + return grpc_connectivity_state_get(&state_tracker_, connectivity_error); +} + +void XdsLb::NotifyOnStateChangeLocked(grpc_connectivity_state* current, + grpc_closure* notify) { + grpc_connectivity_state_notify_on_state_change(&state_tracker_, current, + notify); +} + +void XdsLb::ProcessChannelArgsLocked(const grpc_channel_args& args) { + const grpc_arg* arg = grpc_channel_args_find(&args, GRPC_ARG_LB_ADDRESSES); + if (GPR_UNLIKELY(arg == nullptr || arg->type != GRPC_ARG_POINTER)) { + // Ignore this update. + gpr_log(GPR_ERROR, + "[xdslb %p] No valid LB addresses channel arg in update, ignoring.", + this); + return; + } + const grpc_lb_addresses* addresses = + static_cast<const grpc_lb_addresses*>(arg->value.pointer.p); + // Update fallback address list. + if (fallback_backend_addresses_ != nullptr) { + grpc_lb_addresses_destroy(fallback_backend_addresses_); + } + fallback_backend_addresses_ = ExtractBackendAddresses(addresses); + // Make sure that GRPC_ARG_LB_POLICY_NAME is set in channel args, + // since we use this to trigger the client_load_reporting filter. + static const char* args_to_remove[] = {GRPC_ARG_LB_POLICY_NAME}; + grpc_arg new_arg = grpc_channel_arg_string_create( + (char*)GRPC_ARG_LB_POLICY_NAME, (char*)"xds"); + grpc_channel_args_destroy(args_); + args_ = grpc_channel_args_copy_and_add_and_remove( + &args, args_to_remove, GPR_ARRAY_SIZE(args_to_remove), &new_arg, 1); + // Construct args for balancer channel. + grpc_channel_args* lb_channel_args = + BuildBalancerChannelArgs(addresses, response_generator_.get(), &args); + // Create balancer channel if needed. + if (lb_channel_ == nullptr) { + char* uri_str; + gpr_asprintf(&uri_str, "fake:///%s", server_name_); + gpr_mu_lock(&lb_channel_mu_); + lb_channel_ = grpc_client_channel_factory_create_channel( + client_channel_factory(), uri_str, + GRPC_CLIENT_CHANNEL_TYPE_LOAD_BALANCING, lb_channel_args); + gpr_mu_unlock(&lb_channel_mu_); + GPR_ASSERT(lb_channel_ != nullptr); + gpr_free(uri_str); + } + // Propagate updates to the LB channel (pick_first) through the fake + // resolver. + response_generator_->SetResponse(lb_channel_args); + grpc_channel_args_destroy(lb_channel_args); +} + +void XdsLb::UpdateLocked(const grpc_channel_args& args) { + ProcessChannelArgsLocked(args); + // If fallback is configured and the RR policy already exists, update + // it with the new fallback addresses. + if (lb_fallback_timeout_ms_ > 0 && rr_policy_ != nullptr) { + CreateOrUpdateRoundRobinPolicyLocked(); + } + // Start watching the LB channel connectivity for connection, if not + // already doing so. + if (!watching_lb_channel_) { + lb_channel_connectivity_ = grpc_channel_check_connectivity_state( + lb_channel_, true /* try to connect */); + grpc_channel_element* client_channel_elem = grpc_channel_stack_last_element( + grpc_channel_get_channel_stack(lb_channel_)); + GPR_ASSERT(client_channel_elem->filter == &grpc_client_channel_filter); + watching_lb_channel_ = true; + // TODO(roth): We currently track this ref manually. Once the + // ClosureRef API is ready, we should pass the RefCountedPtr<> along + // with the callback. + auto self = Ref(DEBUG_LOCATION, "watch_lb_channel_connectivity"); + self.release(); + grpc_client_channel_watch_connectivity_state( + client_channel_elem, + grpc_polling_entity_create_from_pollset_set(interested_parties()), + &lb_channel_connectivity_, &lb_channel_on_connectivity_changed_, + nullptr); + } +} + +// +// code for balancer channel and call +// + +void XdsLb::StartPickingLocked() { + // Start a timer to fall back. + if (lb_fallback_timeout_ms_ > 0 && serverlist_ == nullptr && + !fallback_timer_callback_pending_) { + grpc_millis deadline = ExecCtx::Get()->Now() + lb_fallback_timeout_ms_; + // TODO(roth): We currently track this ref manually. Once the + // ClosureRef API is ready, we should pass the RefCountedPtr<> along + // with the callback. + auto self = Ref(DEBUG_LOCATION, "on_fallback_timer"); + self.release(); + GRPC_CLOSURE_INIT(&lb_on_fallback_, &XdsLb::OnFallbackTimerLocked, this, + grpc_combiner_scheduler(combiner())); + fallback_timer_callback_pending_ = true; + grpc_timer_init(&lb_fallback_timer_, deadline, &lb_on_fallback_); + } + started_picking_ = true; + StartBalancerCallLocked(); +} + +void XdsLb::StartBalancerCallLocked() { + GPR_ASSERT(lb_channel_ != nullptr); + if (shutting_down_) return; + // Init the LB call data. + GPR_ASSERT(lb_calld_ == nullptr); + lb_calld_ = MakeOrphanable<BalancerCallState>(Ref()); + if (grpc_lb_xds_trace.enabled()) { + gpr_log(GPR_INFO, + "[xdslb %p] Query for backends (lb_channel: %p, lb_calld: %p)", + this, lb_channel_, lb_calld_.get()); + } + lb_calld_->StartQuery(); +} + +void XdsLb::OnFallbackTimerLocked(void* arg, grpc_error* error) { + XdsLb* xdslb_policy = static_cast<XdsLb*>(arg); + xdslb_policy->fallback_timer_callback_pending_ = false; + // If we receive a serverlist after the timer fires but before this callback + // actually runs, don't fall back. + if (xdslb_policy->serverlist_ == nullptr && !xdslb_policy->shutting_down_ && + error == GRPC_ERROR_NONE) { + if (grpc_lb_xds_trace.enabled()) { + gpr_log(GPR_INFO, "[xdslb %p] Falling back to use backends from resolver", + xdslb_policy); + } + GPR_ASSERT(xdslb_policy->fallback_backend_addresses_ != nullptr); + xdslb_policy->CreateOrUpdateRoundRobinPolicyLocked(); + } + xdslb_policy->Unref(DEBUG_LOCATION, "on_fallback_timer"); +} + +void XdsLb::StartBalancerCallRetryTimerLocked() { + grpc_millis next_try = lb_call_backoff_.NextAttemptTime(); + if (grpc_lb_xds_trace.enabled()) { + gpr_log(GPR_INFO, "[xdslb %p] Connection to LB server lost...", this); + grpc_millis timeout = next_try - ExecCtx::Get()->Now(); + if (timeout > 0) { + gpr_log(GPR_INFO, "[xdslb %p] ... retry_timer_active in %" PRId64 "ms.", + this, timeout); + } else { + gpr_log(GPR_INFO, "[xdslb %p] ... retry_timer_active immediately.", this); + } + } + // TODO(roth): We currently track this ref manually. Once the + // ClosureRef API is ready, we should pass the RefCountedPtr<> along + // with the callback. + auto self = Ref(DEBUG_LOCATION, "on_balancer_call_retry_timer"); + self.release(); + GRPC_CLOSURE_INIT(&lb_on_call_retry_, &XdsLb::OnBalancerCallRetryTimerLocked, + this, grpc_combiner_scheduler(combiner())); + retry_timer_callback_pending_ = true; + grpc_timer_init(&lb_call_retry_timer_, next_try, &lb_on_call_retry_); +} + +void XdsLb::OnBalancerCallRetryTimerLocked(void* arg, grpc_error* error) { + XdsLb* xdslb_policy = static_cast<XdsLb*>(arg); + xdslb_policy->retry_timer_callback_pending_ = false; + if (!xdslb_policy->shutting_down_ && error == GRPC_ERROR_NONE && + xdslb_policy->lb_calld_ == nullptr) { + if (grpc_lb_xds_trace.enabled()) { + gpr_log(GPR_INFO, "[xdslb %p] Restarting call to LB server", + xdslb_policy); + } + xdslb_policy->StartBalancerCallLocked(); + } + xdslb_policy->Unref(DEBUG_LOCATION, "on_balancer_call_retry_timer"); +} + +// Invoked as part of the update process. It continues watching the LB channel +// until it shuts down or becomes READY. It's invoked even if the LB channel +// stayed READY throughout the update (for example if the update is identical). +void XdsLb::OnBalancerChannelConnectivityChangedLocked(void* arg, + grpc_error* error) { + XdsLb* xdslb_policy = static_cast<XdsLb*>(arg); + if (xdslb_policy->shutting_down_) goto done; + // Re-initialize the lb_call. This should also take care of updating the + // embedded RR policy. Note that the current RR policy, if any, will stay in + // effect until an update from the new lb_call is received. + switch (xdslb_policy->lb_channel_connectivity_) { + case GRPC_CHANNEL_CONNECTING: + case GRPC_CHANNEL_TRANSIENT_FAILURE: { + // Keep watching the LB channel. + grpc_channel_element* client_channel_elem = + grpc_channel_stack_last_element( + grpc_channel_get_channel_stack(xdslb_policy->lb_channel_)); + GPR_ASSERT(client_channel_elem->filter == &grpc_client_channel_filter); + grpc_client_channel_watch_connectivity_state( + client_channel_elem, + grpc_polling_entity_create_from_pollset_set( + xdslb_policy->interested_parties()), + &xdslb_policy->lb_channel_connectivity_, + &xdslb_policy->lb_channel_on_connectivity_changed_, nullptr); + break; + } + // The LB channel may be IDLE because it's shut down before the update. + // Restart the LB call to kick the LB channel into gear. + case GRPC_CHANNEL_IDLE: + case GRPC_CHANNEL_READY: + xdslb_policy->lb_calld_.reset(); + if (xdslb_policy->started_picking_) { + if (xdslb_policy->retry_timer_callback_pending_) { + grpc_timer_cancel(&xdslb_policy->lb_call_retry_timer_); + } + xdslb_policy->lb_call_backoff_.Reset(); + xdslb_policy->StartBalancerCallLocked(); + } + [[fallthrough]]; + // Fall through. + case GRPC_CHANNEL_SHUTDOWN: + done: + xdslb_policy->watching_lb_channel_ = false; + xdslb_policy->Unref(DEBUG_LOCATION, + "watch_lb_channel_connectivity_cb_shutdown"); + } +} + +// +// PendingPick +// + +// Adds lb_token of selected subchannel (address) to the call's initial +// metadata. +grpc_error* AddLbTokenToInitialMetadata( + grpc_mdelem lb_token, grpc_linked_mdelem* lb_token_mdelem_storage, + grpc_metadata_batch* initial_metadata) { + GPR_ASSERT(lb_token_mdelem_storage != nullptr); + GPR_ASSERT(!GRPC_MDISNULL(lb_token)); + return grpc_metadata_batch_add_tail(initial_metadata, lb_token_mdelem_storage, + lb_token); +} + +// Destroy function used when embedding client stats in call context. +void DestroyClientStats(void* arg) { + static_cast<XdsLbClientStats*>(arg)->Unref(); +} + +void XdsLb::PendingPickSetMetadataAndContext(PendingPick* pp) { + /* if connected_subchannel is nullptr, no pick has been made by the RR + * policy (e.g., all addresses failed to connect). There won't be any + * user_data/token available */ + if (pp->pick->connected_subchannel != nullptr) { + if (GPR_LIKELY(!GRPC_MDISNULL(pp->lb_token))) { + AddLbTokenToInitialMetadata(GRPC_MDELEM_REF(pp->lb_token), + &pp->pick->lb_token_mdelem_storage, + pp->pick->initial_metadata); + } else { + gpr_log(GPR_ERROR, + "[xdslb %p] No LB token for connected subchannel pick %p", + pp->xdslb_policy, pp->pick); + abort(); + } + // Pass on client stats via context. Passes ownership of the reference. + if (pp->client_stats != nullptr) { + pp->pick->subchannel_call_context[GRPC_GRPCLB_CLIENT_STATS].value = + pp->client_stats.release(); + pp->pick->subchannel_call_context[GRPC_GRPCLB_CLIENT_STATS].destroy = + DestroyClientStats; + } + } else { + pp->client_stats.reset(); + } +} + +/* The \a on_complete closure passed as part of the pick requires keeping a + * reference to its associated round robin instance. We wrap this closure in + * order to unref the round robin instance upon its invocation */ +void XdsLb::OnPendingPickComplete(void* arg, grpc_error* error) { + PendingPick* pp = static_cast<PendingPick*>(arg); + PendingPickSetMetadataAndContext(pp); + GRPC_CLOSURE_SCHED(pp->original_on_complete, GRPC_ERROR_REF(error)); + Delete(pp); +} + +XdsLb::PendingPick* XdsLb::PendingPickCreate(PickState* pick) { + PendingPick* pp = New<PendingPick>(); + pp->xdslb_policy = this; + pp->pick = pick; + GRPC_CLOSURE_INIT(&pp->on_complete, &XdsLb::OnPendingPickComplete, pp, + grpc_schedule_on_exec_ctx); + pp->original_on_complete = pick->on_complete; + pick->on_complete = &pp->on_complete; + return pp; +} + +void XdsLb::AddPendingPick(PendingPick* pp) { + pp->next = pending_picks_; + pending_picks_ = pp; +} + +// +// code for interacting with the RR policy +// + +// Performs a pick over \a rr_policy_. Given that a pick can return +// immediately (ignoring its completion callback), we need to perform the +// cleanups this callback would otherwise be responsible for. +// If \a force_async is true, then we will manually schedule the +// completion callback even if the pick is available immediately. +bool XdsLb::PickFromRoundRobinPolicyLocked(bool force_async, PendingPick* pp, + grpc_error** error) { + // Check for drops if we are not using fallback backend addresses. + if (serverlist_ != nullptr) { + // Look at the index into the serverlist to see if we should drop this call. + xds_grpclb_server* server = serverlist_->servers[serverlist_index_++]; + if (serverlist_index_ == serverlist_->num_servers) { + serverlist_index_ = 0; // Wrap-around. + } + if (server->drop) { + // Update client load reporting stats to indicate the number of + // dropped calls. Note that we have to do this here instead of in + // the client_load_reporting filter, because we do not create a + // subchannel call (and therefore no client_load_reporting filter) + // for dropped calls. + if (lb_calld_ != nullptr && lb_calld_->client_stats() != nullptr) { + lb_calld_->client_stats()->AddCallDroppedLocked( + server->load_balance_token); + } + if (force_async) { + GRPC_CLOSURE_SCHED(pp->original_on_complete, GRPC_ERROR_NONE); + Delete(pp); + return false; + } + Delete(pp); + return true; + } + } + // Set client_stats and user_data. + if (lb_calld_ != nullptr && lb_calld_->client_stats() != nullptr) { + pp->client_stats = lb_calld_->client_stats()->Ref(); + } + GPR_ASSERT(pp->pick->user_data == nullptr); + pp->pick->user_data = (void**)&pp->lb_token; + // Pick via the RR policy. + bool pick_done = rr_policy_->PickLocked(pp->pick, error); + if (pick_done) { + PendingPickSetMetadataAndContext(pp); + if (force_async) { + GRPC_CLOSURE_SCHED(pp->original_on_complete, *error); + *error = GRPC_ERROR_NONE; + pick_done = false; + } + Delete(pp); + } + // else, the pending pick will be registered and taken care of by the + // pending pick list inside the RR policy. Eventually, + // OnPendingPickComplete() will be called, which will (among other + // things) add the LB token to the call's initial metadata. + return pick_done; +} + +void XdsLb::CreateRoundRobinPolicyLocked(const Args& args) { + GPR_ASSERT(rr_policy_ == nullptr); + rr_policy_ = LoadBalancingPolicyRegistry::CreateLoadBalancingPolicy( + "round_robin", args); + if (GPR_UNLIKELY(rr_policy_ == nullptr)) { + gpr_log(GPR_ERROR, "[xdslb %p] Failure creating a RoundRobin policy", this); + return; + } + // TODO(roth): We currently track this ref manually. Once the new + // ClosureRef API is done, pass the RefCountedPtr<> along with the closure. + auto self = Ref(DEBUG_LOCATION, "on_rr_reresolution_requested"); + self.release(); + rr_policy_->SetReresolutionClosureLocked(&on_rr_request_reresolution_); + grpc_error* rr_state_error = nullptr; + rr_connectivity_state_ = rr_policy_->CheckConnectivityLocked(&rr_state_error); + // Connectivity state is a function of the RR policy updated/created. + UpdateConnectivityStateFromRoundRobinPolicyLocked(rr_state_error); + // Add the gRPC LB's interested_parties pollset_set to that of the newly + // created RR policy. This will make the RR policy progress upon activity on + // gRPC LB, which in turn is tied to the application's call. + grpc_pollset_set_add_pollset_set(rr_policy_->interested_parties(), + interested_parties()); + // Subscribe to changes to the connectivity of the new RR. + // TODO(roth): We currently track this ref manually. Once the new + // ClosureRef API is done, pass the RefCountedPtr<> along with the closure. + self = Ref(DEBUG_LOCATION, "on_rr_connectivity_changed"); + self.release(); + rr_policy_->NotifyOnStateChangeLocked(&rr_connectivity_state_, + &on_rr_connectivity_changed_); + rr_policy_->ExitIdleLocked(); + // Send pending picks to RR policy. + PendingPick* pp; + while ((pp = pending_picks_)) { + pending_picks_ = pp->next; + if (grpc_lb_xds_trace.enabled()) { + gpr_log(GPR_INFO, + "[xdslb %p] Pending pick about to (async) PICK from RR %p", this, + rr_policy_.get()); + } + grpc_error* error = GRPC_ERROR_NONE; + PickFromRoundRobinPolicyLocked(true /* force_async */, pp, &error); + } +} + +grpc_channel_args* XdsLb::CreateRoundRobinPolicyArgsLocked() { + grpc_lb_addresses* addresses; + bool is_backend_from_grpclb_load_balancer = false; + if (serverlist_ != nullptr) { + GPR_ASSERT(serverlist_->num_servers > 0); + addresses = ProcessServerlist(serverlist_); + is_backend_from_grpclb_load_balancer = true; + } else { + // If CreateOrUpdateRoundRobinPolicyLocked() is invoked when we haven't + // received any serverlist from the balancer, we use the fallback backends + // returned by the resolver. Note that the fallback backend list may be + // empty, in which case the new round_robin policy will keep the requested + // picks pending. + GPR_ASSERT(fallback_backend_addresses_ != nullptr); + addresses = grpc_lb_addresses_copy(fallback_backend_addresses_); + } + GPR_ASSERT(addresses != nullptr); + // Replace the LB addresses in the channel args that we pass down to + // the subchannel. + static const char* keys_to_remove[] = {GRPC_ARG_LB_ADDRESSES}; + const grpc_arg args_to_add[] = { + grpc_lb_addresses_create_channel_arg(addresses), + // A channel arg indicating if the target is a backend inferred from a + // grpclb load balancer. + grpc_channel_arg_integer_create( + const_cast<char*>(GRPC_ARG_ADDRESS_IS_BACKEND_FROM_XDS_LOAD_BALANCER), + is_backend_from_grpclb_load_balancer), + }; + grpc_channel_args* args = grpc_channel_args_copy_and_add_and_remove( + args_, keys_to_remove, GPR_ARRAY_SIZE(keys_to_remove), args_to_add, + GPR_ARRAY_SIZE(args_to_add)); + grpc_lb_addresses_destroy(addresses); + return args; +} + +void XdsLb::CreateOrUpdateRoundRobinPolicyLocked() { + if (shutting_down_) return; + grpc_channel_args* args = CreateRoundRobinPolicyArgsLocked(); + GPR_ASSERT(args != nullptr); + if (rr_policy_ != nullptr) { + if (grpc_lb_xds_trace.enabled()) { + gpr_log(GPR_INFO, "[xdslb %p] Updating RR policy %p", this, + rr_policy_.get()); + } + rr_policy_->UpdateLocked(*args); + } else { + LoadBalancingPolicy::Args lb_policy_args; + lb_policy_args.combiner = combiner(); + lb_policy_args.client_channel_factory = client_channel_factory(); + lb_policy_args.args = args; + CreateRoundRobinPolicyLocked(lb_policy_args); + if (grpc_lb_xds_trace.enabled()) { + gpr_log(GPR_INFO, "[xdslb %p] Created new RR policy %p", this, + rr_policy_.get()); + } + } + grpc_channel_args_destroy(args); +} + +void XdsLb::OnRoundRobinRequestReresolutionLocked(void* arg, + grpc_error* error) { + XdsLb* xdslb_policy = static_cast<XdsLb*>(arg); + if (xdslb_policy->shutting_down_ || error != GRPC_ERROR_NONE) { + xdslb_policy->Unref(DEBUG_LOCATION, "on_rr_reresolution_requested"); + return; + } + if (grpc_lb_xds_trace.enabled()) { + gpr_log( + GPR_INFO, + "[xdslb %p] Re-resolution requested from the internal RR policy (%p).", + xdslb_policy, xdslb_policy->rr_policy_.get()); + } + // If we are talking to a balancer, we expect to get updated addresses form + // the balancer, so we can ignore the re-resolution request from the RR + // policy. Otherwise, handle the re-resolution request using the + // grpclb policy's original re-resolution closure. + if (xdslb_policy->lb_calld_ == nullptr || + !xdslb_policy->lb_calld_->seen_initial_response()) { + xdslb_policy->TryReresolutionLocked(&grpc_lb_xds_trace, GRPC_ERROR_NONE); + } + // Give back the wrapper closure to the RR policy. + xdslb_policy->rr_policy_->SetReresolutionClosureLocked( + &xdslb_policy->on_rr_request_reresolution_); +} + +void XdsLb::UpdateConnectivityStateFromRoundRobinPolicyLocked( + grpc_error* rr_state_error) { + const grpc_connectivity_state curr_glb_state = + grpc_connectivity_state_check(&state_tracker_); + /* The new connectivity status is a function of the previous one and the new + * input coming from the status of the RR policy. + * + * current state (grpclb's) + * | + * v || I | C | R | TF | SD | <- new state (RR's) + * ===++====+=====+=====+======+======+ + * I || I | C | R | [I] | [I] | + * ---++----+-----+-----+------+------+ + * C || I | C | R | [C] | [C] | + * ---++----+-----+-----+------+------+ + * R || I | C | R | [R] | [R] | + * ---++----+-----+-----+------+------+ + * TF || I | C | R | [TF] | [TF] | + * ---++----+-----+-----+------+------+ + * SD || NA | NA | NA | NA | NA | (*) + * ---++----+-----+-----+------+------+ + * + * A [STATE] indicates that the old RR policy is kept. In those cases, STATE + * is the current state of grpclb, which is left untouched. + * + * In summary, if the new state is TRANSIENT_FAILURE or SHUTDOWN, stick to + * the previous RR instance. + * + * Note that the status is never updated to SHUTDOWN as a result of calling + * this function. Only glb_shutdown() has the power to set that state. + * + * (*) This function mustn't be called during shutting down. */ + GPR_ASSERT(curr_glb_state != GRPC_CHANNEL_SHUTDOWN); + switch (rr_connectivity_state_) { + case GRPC_CHANNEL_TRANSIENT_FAILURE: + case GRPC_CHANNEL_SHUTDOWN: + GPR_ASSERT(rr_state_error != GRPC_ERROR_NONE); + break; + case GRPC_CHANNEL_IDLE: + case GRPC_CHANNEL_CONNECTING: + case GRPC_CHANNEL_READY: + GPR_ASSERT(rr_state_error == GRPC_ERROR_NONE); + } + if (grpc_lb_xds_trace.enabled()) { + gpr_log( + GPR_INFO, + "[xdslb %p] Setting grpclb's state to %s from new RR policy %p state.", + this, grpc_connectivity_state_name(rr_connectivity_state_), + rr_policy_.get()); + } + grpc_connectivity_state_set(&state_tracker_, rr_connectivity_state_, + rr_state_error, + "update_lb_connectivity_status_locked"); +} + +void XdsLb::OnRoundRobinConnectivityChangedLocked(void* arg, + grpc_error* error) { + XdsLb* xdslb_policy = static_cast<XdsLb*>(arg); + if (xdslb_policy->shutting_down_) { + xdslb_policy->Unref(DEBUG_LOCATION, "on_rr_connectivity_changed"); + return; + } + xdslb_policy->UpdateConnectivityStateFromRoundRobinPolicyLocked( + GRPC_ERROR_REF(error)); + // Resubscribe. Reuse the "on_rr_connectivity_changed" ref. + xdslb_policy->rr_policy_->NotifyOnStateChangeLocked( + &xdslb_policy->rr_connectivity_state_, + &xdslb_policy->on_rr_connectivity_changed_); +} + +// +// factory +// + +class XdsFactory : public LoadBalancingPolicyFactory { + public: + OrphanablePtr<LoadBalancingPolicy> CreateLoadBalancingPolicy( + const LoadBalancingPolicy::Args& args) const override { + /* Count the number of gRPC-LB addresses. There must be at least one. */ + const grpc_arg* arg = + grpc_channel_args_find(args.args, GRPC_ARG_LB_ADDRESSES); + if (arg == nullptr || arg->type != GRPC_ARG_POINTER) { + return nullptr; + } + grpc_lb_addresses* addresses = + static_cast<grpc_lb_addresses*>(arg->value.pointer.p); + size_t num_grpclb_addrs = 0; + for (size_t i = 0; i < addresses->num_addresses; ++i) { + if (addresses->addresses[i].is_balancer) ++num_grpclb_addrs; + } + if (num_grpclb_addrs == 0) return nullptr; + return OrphanablePtr<LoadBalancingPolicy>(New<XdsLb>(addresses, args)); + } + + const char* name() const override { return "xds"; } +}; + +} // namespace + +} // namespace grpc_core + +// +// Plugin registration +// + +namespace { + +// Only add client_load_reporting filter if the grpclb LB policy is used. +bool maybe_add_client_load_reporting_filter(grpc_channel_stack_builder* builder, + void* arg) { + const grpc_channel_args* args = + grpc_channel_stack_builder_get_channel_arguments(builder); + const grpc_arg* channel_arg = + grpc_channel_args_find(args, GRPC_ARG_LB_POLICY_NAME); + if (channel_arg != nullptr && channel_arg->type == GRPC_ARG_STRING && + strcmp(channel_arg->value.string, "grpclb") == 0) { + return grpc_channel_stack_builder_append_filter( + builder, (const grpc_channel_filter*)arg, nullptr, nullptr); + } + return true; +} + +} // namespace + +void grpc_lb_policy_xds_init() { + grpc_core::LoadBalancingPolicyRegistry::Builder:: + RegisterLoadBalancingPolicyFactory( + grpc_core::UniquePtr<grpc_core::LoadBalancingPolicyFactory>( + grpc_core::New<grpc_core::XdsFactory>())); + grpc_channel_init_register_stage(GRPC_CLIENT_SUBCHANNEL, + GRPC_CHANNEL_INIT_BUILTIN_PRIORITY, + maybe_add_client_load_reporting_filter, + (void*)&xds_client_load_reporting_filter); +} + +void grpc_lb_policy_xds_shutdown() {} |