diff options
Diffstat (limited to 'src/core/ext/filters/client_channel/resolver/dns/c_ares/dns_resolver_ares.cc')
-rw-r--r-- | src/core/ext/filters/client_channel/resolver/dns/c_ares/dns_resolver_ares.cc | 456 |
1 files changed, 456 insertions, 0 deletions
diff --git a/src/core/ext/filters/client_channel/resolver/dns/c_ares/dns_resolver_ares.cc b/src/core/ext/filters/client_channel/resolver/dns/c_ares/dns_resolver_ares.cc new file mode 100644 index 0000000000..5f7ab987cb --- /dev/null +++ b/src/core/ext/filters/client_channel/resolver/dns/c_ares/dns_resolver_ares.cc @@ -0,0 +1,456 @@ +/* + * + * Copyright 2015 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. + * + */ + +#include <grpc/support/port_platform.h> +#if GRPC_ARES == 1 && !defined(GRPC_UV) + +#include <limits.h> +#include <stdio.h> +#include <string.h> +#include <unistd.h> + +#include <grpc/support/alloc.h> +#include <grpc/support/host_port.h> +#include <grpc/support/string_util.h> + +#include "src/core/ext/filters/client_channel/http_connect_handshaker.h" +#include "src/core/ext/filters/client_channel/lb_policy_registry.h" +#include "src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper.h" +#include "src/core/ext/filters/client_channel/resolver_registry.h" +#include "src/core/lib/backoff/backoff.h" +#include "src/core/lib/channel/channel_args.h" +#include "src/core/lib/iomgr/combiner.h" +#include "src/core/lib/iomgr/gethostname.h" +#include "src/core/lib/iomgr/resolve_address.h" +#include "src/core/lib/iomgr/timer.h" +#include "src/core/lib/json/json.h" +#include "src/core/lib/support/env.h" +#include "src/core/lib/support/string.h" +#include "src/core/lib/transport/service_config.h" + +#define GRPC_DNS_MIN_CONNECT_TIMEOUT_SECONDS 1 +#define GRPC_DNS_INITIAL_CONNECT_BACKOFF_SECONDS 1 +#define GRPC_DNS_RECONNECT_BACKOFF_MULTIPLIER 1.6 +#define GRPC_DNS_RECONNECT_MAX_BACKOFF_SECONDS 120 +#define GRPC_DNS_RECONNECT_JITTER 0.2 + +typedef struct { + /** base class: must be first */ + grpc_resolver base; + /** DNS server to use (if not system default) */ + char *dns_server; + /** name to resolve (usually the same as target_name) */ + char *name_to_resolve; + /** default port to use */ + char *default_port; + /** channel args. */ + grpc_channel_args *channel_args; + /** whether to request the service config */ + bool request_service_config; + /** pollset_set to drive the name resolution process */ + grpc_pollset_set *interested_parties; + + /** Closures used by the combiner */ + grpc_closure dns_ares_on_retry_timer_locked; + grpc_closure dns_ares_on_resolved_locked; + + /** Combiner guarding the rest of the state */ + grpc_combiner *combiner; + /** are we currently resolving? */ + bool resolving; + /** the pending resolving request */ + grpc_ares_request *pending_request; + /** which version of the result have we published? */ + int published_version; + /** which version of the result is current? */ + int resolved_version; + /** pending next completion, or NULL */ + grpc_closure *next_completion; + /** target result address for next completion */ + grpc_channel_args **target_result; + /** current (fully resolved) result */ + grpc_channel_args *resolved_result; + /** retry timer */ + bool have_retry_timer; + grpc_timer retry_timer; + /** retry backoff state */ + grpc_backoff backoff_state; + + /** currently resolving addresses */ + grpc_lb_addresses *lb_addresses; + /** currently resolving service config */ + char *service_config_json; +} ares_dns_resolver; + +static void dns_ares_destroy(grpc_exec_ctx *exec_ctx, grpc_resolver *r); + +static void dns_ares_start_resolving_locked(grpc_exec_ctx *exec_ctx, + ares_dns_resolver *r); +static void dns_ares_maybe_finish_next_locked(grpc_exec_ctx *exec_ctx, + ares_dns_resolver *r); + +static void dns_ares_shutdown_locked(grpc_exec_ctx *exec_ctx, grpc_resolver *r); +static void dns_ares_channel_saw_error_locked(grpc_exec_ctx *exec_ctx, + grpc_resolver *r); +static void dns_ares_next_locked(grpc_exec_ctx *exec_ctx, grpc_resolver *r, + grpc_channel_args **target_result, + grpc_closure *on_complete); + +static const grpc_resolver_vtable dns_ares_resolver_vtable = { + dns_ares_destroy, dns_ares_shutdown_locked, + dns_ares_channel_saw_error_locked, dns_ares_next_locked}; + +static void dns_ares_shutdown_locked(grpc_exec_ctx *exec_ctx, + grpc_resolver *resolver) { + ares_dns_resolver *r = (ares_dns_resolver *)resolver; + if (r->have_retry_timer) { + grpc_timer_cancel(exec_ctx, &r->retry_timer); + } + if (r->pending_request != NULL) { + grpc_cancel_ares_request(exec_ctx, r->pending_request); + } + if (r->next_completion != NULL) { + *r->target_result = NULL; + GRPC_CLOSURE_SCHED( + exec_ctx, r->next_completion, + GRPC_ERROR_CREATE_FROM_STATIC_STRING("Resolver Shutdown")); + r->next_completion = NULL; + } +} + +static void dns_ares_channel_saw_error_locked(grpc_exec_ctx *exec_ctx, + grpc_resolver *resolver) { + ares_dns_resolver *r = (ares_dns_resolver *)resolver; + if (!r->resolving) { + grpc_backoff_reset(&r->backoff_state); + dns_ares_start_resolving_locked(exec_ctx, r); + } +} + +static void dns_ares_on_retry_timer_locked(grpc_exec_ctx *exec_ctx, void *arg, + grpc_error *error) { + ares_dns_resolver *r = (ares_dns_resolver *)arg; + r->have_retry_timer = false; + if (error == GRPC_ERROR_NONE) { + if (!r->resolving) { + dns_ares_start_resolving_locked(exec_ctx, r); + } + } + GRPC_RESOLVER_UNREF(exec_ctx, &r->base, "retry-timer"); +} + +static bool value_in_json_array(grpc_json *array, const char *value) { + for (grpc_json *entry = array->child; entry != NULL; entry = entry->next) { + if (entry->type == GRPC_JSON_STRING && strcmp(entry->value, value) == 0) { + return true; + } + } + return false; +} + +static char *choose_service_config(char *service_config_choice_json) { + grpc_json *choices_json = grpc_json_parse_string(service_config_choice_json); + if (choices_json == NULL || choices_json->type != GRPC_JSON_ARRAY) { + gpr_log(GPR_ERROR, "cannot parse service config JSON string"); + return NULL; + } + char *service_config = NULL; + for (grpc_json *choice = choices_json->child; choice != NULL; + choice = choice->next) { + if (choice->type != GRPC_JSON_OBJECT) { + gpr_log(GPR_ERROR, "cannot parse service config JSON string"); + break; + } + grpc_json *service_config_json = NULL; + for (grpc_json *field = choice->child; field != NULL; field = field->next) { + // Check client language, if specified. + if (strcmp(field->key, "clientLanguage") == 0) { + if (field->type != GRPC_JSON_ARRAY || + !value_in_json_array(field, "c++")) { + service_config_json = NULL; + break; + } + } + // Check client hostname, if specified. + if (strcmp(field->key, "clientHostname") == 0) { + char *hostname = grpc_gethostname(); + if (hostname == NULL || field->type != GRPC_JSON_ARRAY || + !value_in_json_array(field, hostname)) { + service_config_json = NULL; + break; + } + } + // Check percentage, if specified. + if (strcmp(field->key, "percentage") == 0) { + if (field->type != GRPC_JSON_NUMBER) { + service_config_json = NULL; + break; + } + int random_pct = rand() % 100; + int percentage; + if (sscanf(field->value, "%d", &percentage) != 1 || + random_pct > percentage || percentage == 0) { + service_config_json = NULL; + break; + } + } + // Save service config. + if (strcmp(field->key, "serviceConfig") == 0) { + if (field->type == GRPC_JSON_OBJECT) { + service_config_json = field; + } + } + } + if (service_config_json != NULL) { + service_config = grpc_json_dump_to_string(service_config_json, 0); + break; + } + } + grpc_json_destroy(choices_json); + return service_config; +} + +static void dns_ares_on_resolved_locked(grpc_exec_ctx *exec_ctx, void *arg, + grpc_error *error) { + ares_dns_resolver *r = (ares_dns_resolver *)arg; + grpc_channel_args *result = NULL; + GPR_ASSERT(r->resolving); + r->resolving = false; + r->pending_request = NULL; + if (r->lb_addresses != NULL) { + static const char *args_to_remove[2]; + size_t num_args_to_remove = 0; + grpc_arg new_args[3]; + size_t num_args_to_add = 0; + new_args[num_args_to_add++] = + grpc_lb_addresses_create_channel_arg(r->lb_addresses); + grpc_service_config *service_config = NULL; + char *service_config_string = NULL; + if (r->service_config_json != NULL) { + service_config_string = choose_service_config(r->service_config_json); + gpr_free(r->service_config_json); + if (service_config_string != NULL) { + gpr_log(GPR_INFO, "selected service config choice: %s", + service_config_string); + args_to_remove[num_args_to_remove++] = GRPC_ARG_SERVICE_CONFIG; + new_args[num_args_to_add++] = grpc_channel_arg_string_create( + (char *)GRPC_ARG_SERVICE_CONFIG, service_config_string); + service_config = grpc_service_config_create(service_config_string); + if (service_config != NULL) { + const char *lb_policy_name = + grpc_service_config_get_lb_policy_name(service_config); + if (lb_policy_name != NULL) { + args_to_remove[num_args_to_remove++] = GRPC_ARG_LB_POLICY_NAME; + new_args[num_args_to_add++] = grpc_channel_arg_string_create( + (char *)GRPC_ARG_LB_POLICY_NAME, (char *)lb_policy_name); + } + } + } + } + result = grpc_channel_args_copy_and_add_and_remove( + r->channel_args, args_to_remove, num_args_to_remove, new_args, + num_args_to_add); + if (service_config != NULL) grpc_service_config_destroy(service_config); + gpr_free(service_config_string); + grpc_lb_addresses_destroy(exec_ctx, r->lb_addresses); + } else { + const char *msg = grpc_error_string(error); + gpr_log(GPR_DEBUG, "dns resolution failed: %s", msg); + grpc_millis next_try = grpc_backoff_step(exec_ctx, &r->backoff_state); + grpc_millis timeout = next_try - grpc_exec_ctx_now(exec_ctx); + gpr_log(GPR_INFO, "dns resolution failed (will retry): %s", + grpc_error_string(error)); + GPR_ASSERT(!r->have_retry_timer); + r->have_retry_timer = true; + GRPC_RESOLVER_REF(&r->base, "retry-timer"); + if (timeout > 0) { + gpr_log(GPR_DEBUG, "retrying in %" PRIdPTR " milliseconds", timeout); + } else { + gpr_log(GPR_DEBUG, "retrying immediately"); + } + grpc_timer_init(exec_ctx, &r->retry_timer, next_try, + &r->dns_ares_on_retry_timer_locked); + } + if (r->resolved_result != NULL) { + grpc_channel_args_destroy(exec_ctx, r->resolved_result); + } + r->resolved_result = result; + r->resolved_version++; + dns_ares_maybe_finish_next_locked(exec_ctx, r); + GRPC_RESOLVER_UNREF(exec_ctx, &r->base, "dns-resolving"); +} + +static void dns_ares_next_locked(grpc_exec_ctx *exec_ctx, + grpc_resolver *resolver, + grpc_channel_args **target_result, + grpc_closure *on_complete) { + gpr_log(GPR_DEBUG, "dns_ares_next is called."); + ares_dns_resolver *r = (ares_dns_resolver *)resolver; + GPR_ASSERT(!r->next_completion); + r->next_completion = on_complete; + r->target_result = target_result; + if (r->resolved_version == 0 && !r->resolving) { + grpc_backoff_reset(&r->backoff_state); + dns_ares_start_resolving_locked(exec_ctx, r); + } else { + dns_ares_maybe_finish_next_locked(exec_ctx, r); + } +} + +static void dns_ares_start_resolving_locked(grpc_exec_ctx *exec_ctx, + ares_dns_resolver *r) { + GRPC_RESOLVER_REF(&r->base, "dns-resolving"); + GPR_ASSERT(!r->resolving); + r->resolving = true; + r->lb_addresses = NULL; + r->service_config_json = NULL; + r->pending_request = grpc_dns_lookup_ares( + exec_ctx, r->dns_server, r->name_to_resolve, r->default_port, + r->interested_parties, &r->dns_ares_on_resolved_locked, &r->lb_addresses, + true /* check_grpclb */, + r->request_service_config ? &r->service_config_json : NULL); +} + +static void dns_ares_maybe_finish_next_locked(grpc_exec_ctx *exec_ctx, + ares_dns_resolver *r) { + if (r->next_completion != NULL && + r->resolved_version != r->published_version) { + *r->target_result = r->resolved_result == NULL + ? NULL + : grpc_channel_args_copy(r->resolved_result); + gpr_log(GPR_DEBUG, "dns_ares_maybe_finish_next_locked"); + GRPC_CLOSURE_SCHED(exec_ctx, r->next_completion, GRPC_ERROR_NONE); + r->next_completion = NULL; + r->published_version = r->resolved_version; + } +} + +static void dns_ares_destroy(grpc_exec_ctx *exec_ctx, grpc_resolver *gr) { + gpr_log(GPR_DEBUG, "dns_ares_destroy"); + ares_dns_resolver *r = (ares_dns_resolver *)gr; + if (r->resolved_result != NULL) { + grpc_channel_args_destroy(exec_ctx, r->resolved_result); + } + grpc_pollset_set_destroy(exec_ctx, r->interested_parties); + gpr_free(r->dns_server); + gpr_free(r->name_to_resolve); + gpr_free(r->default_port); + grpc_channel_args_destroy(exec_ctx, r->channel_args); + gpr_free(r); +} + +static grpc_resolver *dns_ares_create(grpc_exec_ctx *exec_ctx, + grpc_resolver_args *args, + const char *default_port) { + /* Get name from args. */ + const char *path = args->uri->path; + if (path[0] == '/') ++path; + /* Create resolver. */ + ares_dns_resolver *r = + (ares_dns_resolver *)gpr_zalloc(sizeof(ares_dns_resolver)); + grpc_resolver_init(&r->base, &dns_ares_resolver_vtable, args->combiner); + if (0 != strcmp(args->uri->authority, "")) { + r->dns_server = gpr_strdup(args->uri->authority); + } + r->name_to_resolve = gpr_strdup(path); + r->default_port = gpr_strdup(default_port); + r->channel_args = grpc_channel_args_copy(args->args); + const grpc_arg *arg = grpc_channel_args_find( + r->channel_args, GRPC_ARG_SERVICE_CONFIG_DISABLE_RESOLUTION); + r->request_service_config = !grpc_channel_arg_get_integer( + arg, (grpc_integer_options){false, false, true}); + r->interested_parties = grpc_pollset_set_create(); + if (args->pollset_set != NULL) { + grpc_pollset_set_add_pollset_set(exec_ctx, r->interested_parties, + args->pollset_set); + } + grpc_backoff_init(&r->backoff_state, GRPC_DNS_INITIAL_CONNECT_BACKOFF_SECONDS, + GRPC_DNS_RECONNECT_BACKOFF_MULTIPLIER, + GRPC_DNS_RECONNECT_JITTER, + GRPC_DNS_MIN_CONNECT_TIMEOUT_SECONDS * 1000, + GRPC_DNS_RECONNECT_MAX_BACKOFF_SECONDS * 1000); + GRPC_CLOSURE_INIT(&r->dns_ares_on_retry_timer_locked, + dns_ares_on_retry_timer_locked, r, + grpc_combiner_scheduler(r->base.combiner)); + GRPC_CLOSURE_INIT(&r->dns_ares_on_resolved_locked, + dns_ares_on_resolved_locked, r, + grpc_combiner_scheduler(r->base.combiner)); + return &r->base; +} + +/* + * FACTORY + */ + +static void dns_ares_factory_ref(grpc_resolver_factory *factory) {} + +static void dns_ares_factory_unref(grpc_resolver_factory *factory) {} + +static grpc_resolver *dns_factory_create_resolver( + grpc_exec_ctx *exec_ctx, grpc_resolver_factory *factory, + grpc_resolver_args *args) { + return dns_ares_create(exec_ctx, args, "https"); +} + +static char *dns_ares_factory_get_default_host_name( + grpc_resolver_factory *factory, grpc_uri *uri) { + const char *path = uri->path; + if (path[0] == '/') ++path; + return gpr_strdup(path); +} + +static const grpc_resolver_factory_vtable dns_ares_factory_vtable = { + dns_ares_factory_ref, dns_ares_factory_unref, dns_factory_create_resolver, + dns_ares_factory_get_default_host_name, "dns"}; +static grpc_resolver_factory dns_resolver_factory = {&dns_ares_factory_vtable}; + +static grpc_resolver_factory *dns_ares_resolver_factory_create() { + return &dns_resolver_factory; +} + +extern "C" void grpc_resolver_dns_ares_init(void) { + char *resolver = gpr_getenv("GRPC_DNS_RESOLVER"); + /* TODO(zyc): Turn on c-ares based resolver by default after the address + sorter and the CNAME support are added. */ + if (resolver != NULL && gpr_stricmp(resolver, "ares") == 0) { + grpc_error *error = grpc_ares_init(); + if (error != GRPC_ERROR_NONE) { + GRPC_LOG_IF_ERROR("ares_library_init() failed", error); + return; + } + grpc_resolve_address = grpc_resolve_address_ares; + grpc_register_resolver_type(dns_ares_resolver_factory_create()); + } + gpr_free(resolver); +} + +extern "C" void grpc_resolver_dns_ares_shutdown(void) { + char *resolver = gpr_getenv("GRPC_DNS_RESOLVER"); + if (resolver != NULL && gpr_stricmp(resolver, "ares") == 0) { + grpc_ares_cleanup(); + } + gpr_free(resolver); +} + +#else /* GRPC_ARES == 1 && !defined(GRPC_UV) */ + +extern "C" void grpc_resolver_dns_ares_init(void) {} + +extern "C" void grpc_resolver_dns_ares_shutdown(void) {} + +#endif /* GRPC_ARES == 1 && !defined(GRPC_UV) */ |