Merge pull request #8618 from markdroth/channel_info_api

Add API for getting arbitrary state back from a channel

20 files changed, 100 insertions, 13 deletions

diff --git a/src/core/ext/census/grpc_filter.c b/src/core/ext/census/grpc_filter.c
index 5a283de468..397dbc40a8 100644
--- a/src/core/ext/census/grpc_filter.c
+++ b/src/core/ext/census/grpc_filter.c
@@ -191,6 +191,7 @@ const grpc_channel_filter grpc_client_census_filter = {
     init_channel_elem,
     destroy_channel_elem,
     grpc_call_next_get_peer,
+    grpc_channel_next_get_info,
     "census-client"};
 
 const grpc_channel_filter grpc_server_census_filter = {
@@ -204,4 +205,5 @@ const grpc_channel_filter grpc_server_census_filter = {
     init_channel_elem,
     destroy_channel_elem,
     grpc_call_next_get_peer,
+    grpc_channel_next_get_info,
     "census-server"};
diff --git a/src/core/ext/client_channel/client_channel.c b/src/core/ext/client_channel/client_channel.c
index ff773ac334..1cce3bc329 100644
--- a/src/core/ext/client_channel/client_channel.c
+++ b/src/core/ext/client_channel/client_channel.c
@@ -39,6 +39,7 @@
 
 #include <grpc/support/alloc.h>
 #include <grpc/support/log.h>
+#include <grpc/support/string_util.h>
 #include <grpc/support/sync.h>
 #include <grpc/support/useful.h>
 
@@ -123,6 +124,7 @@ typedef struct client_channel_channel_data {
   /** mutex protecting all variables below in this data structure */
   gpr_mu mu;
   /** currently active load balancer */
+  char *lb_policy_name;
   grpc_lb_policy *lb_policy;
   /** maps method names to method_parameters structs */
   grpc_mdstr_hash_table *method_params_table;
@@ -223,6 +225,7 @@ static void watch_lb_policy(grpc_exec_ctx *exec_ctx, channel_data *chand,
 static void on_resolver_result_changed(grpc_exec_ctx *exec_ctx, void *arg,
                                        grpc_error *error) {
   channel_data *chand = arg;
+  char *lb_policy_name = NULL;
   grpc_lb_policy *lb_policy = NULL;
   grpc_lb_policy *old_lb_policy;
   grpc_mdstr_hash_table *method_params_table = NULL;
@@ -236,7 +239,6 @@ static void on_resolver_result_changed(grpc_exec_ctx *exec_ctx, void *arg,
     lb_policy_args.client_channel_factory = chand->client_channel_factory;
 
     // Find LB policy name.
-    const char *lb_policy_name = NULL;
     const grpc_arg *channel_arg =
         grpc_channel_args_find(lb_policy_args.args, GRPC_ARG_LB_POLICY_NAME);
     if (channel_arg != NULL) {
@@ -289,6 +291,10 @@ static void on_resolver_result_changed(grpc_exec_ctx *exec_ctx, void *arg,
           (grpc_method_config_table *)channel_arg->value.pointer.p,
           method_config_convert_value, &method_parameters_vtable);
     }
+    // Before we clean up, save a copy of lb_policy_name, since it might
+    // be pointing to data inside chand->resolver_result.
+    // The copy will be saved in chand->lb_policy_name below.
+    lb_policy_name = gpr_strdup(lb_policy_name);
     grpc_channel_args_destroy(chand->resolver_result);
     chand->resolver_result = NULL;
   }
@@ -299,6 +305,10 @@ static void on_resolver_result_changed(grpc_exec_ctx *exec_ctx, void *arg,
   }
 
   gpr_mu_lock(&chand->mu);
+  if (lb_policy_name != NULL) {
+    gpr_free(chand->lb_policy_name);
+    chand->lb_policy_name = lb_policy_name;
+  }
   old_lb_policy = chand->lb_policy;
   chand->lb_policy = lb_policy;
   if (chand->method_params_table != NULL) {
@@ -426,6 +436,19 @@ static void cc_start_transport_op(grpc_exec_ctx *exec_ctx,
   gpr_mu_unlock(&chand->mu);
 }
 
+static void cc_get_channel_info(grpc_exec_ctx *exec_ctx,
+                                grpc_channel_element *elem,
+                                const grpc_channel_info *info) {
+  channel_data *chand = elem->channel_data;
+  gpr_mu_lock(&chand->mu);
+  if (info->lb_policy_name != NULL) {
+    *info->lb_policy_name = chand->lb_policy_name == NULL
+                                ? NULL
+                                : gpr_strdup(chand->lb_policy_name);
+  }
+  gpr_mu_unlock(&chand->mu);
+}
+
 /* Constructor for channel_data */
 static void cc_init_channel_elem(grpc_exec_ctx *exec_ctx,
                                  grpc_channel_element *elem,
@@ -465,6 +488,7 @@ static void cc_destroy_channel_elem(grpc_exec_ctx *exec_ctx,
                                      chand->interested_parties);
     GRPC_LB_POLICY_UNREF(exec_ctx, chand->lb_policy, "channel");
   }
+  gpr_free(chand->lb_policy_name);
   if (chand->method_params_table != NULL) {
     grpc_mdstr_hash_table_unref(chand->method_params_table);
   }
@@ -1052,6 +1076,7 @@ const grpc_channel_filter grpc_client_channel_filter = {
     cc_init_channel_elem,
     cc_destroy_channel_elem,
     cc_get_peer,
+    cc_get_channel_info,
     "client-channel",
 };
 
diff --git a/src/core/ext/load_reporting/load_reporting_filter.c b/src/core/ext/load_reporting/load_reporting_filter.c
index eeae2400fb..b810e20bb9 100644
--- a/src/core/ext/load_reporting/load_reporting_filter.c
+++ b/src/core/ext/load_reporting/load_reporting_filter.c
@@ -232,4 +232,5 @@ const grpc_channel_filter grpc_load_reporting_filter = {
     init_channel_elem,
     destroy_channel_elem,
     grpc_call_next_get_peer,
+    grpc_channel_next_get_info,
     "load_reporting"};
diff --git a/src/core/lib/channel/channel_stack.c b/src/core/lib/channel/channel_stack.c
index 9da81959e7..98ee03417f 100644
--- a/src/core/lib/channel/channel_stack.c
+++ b/src/core/lib/channel/channel_stack.c
@@ -255,6 +255,13 @@ char *grpc_call_next_get_peer(grpc_exec_ctx *exec_ctx,
   return next_elem->filter->get_peer(exec_ctx, next_elem);
 }
 
+void grpc_channel_next_get_info(grpc_exec_ctx *exec_ctx,
+                                grpc_channel_element *elem,
+                                const grpc_channel_info *channel_info) {
+  grpc_channel_element *next_elem = elem + 1;
+  next_elem->filter->get_channel_info(exec_ctx, next_elem, channel_info);
+}
+
 void grpc_channel_next_op(grpc_exec_ctx *exec_ctx, grpc_channel_element *elem,
                           grpc_transport_op *op) {
   grpc_channel_element *next_elem = elem + 1;
diff --git a/src/core/lib/channel/channel_stack.h b/src/core/lib/channel/channel_stack.h
index 0d58994726..c3b662c969 100644
--- a/src/core/lib/channel/channel_stack.h
+++ b/src/core/lib/channel/channel_stack.h
@@ -156,6 +156,10 @@ typedef struct {
   /* Implement grpc_call_get_peer() */
   char *(*get_peer)(grpc_exec_ctx *exec_ctx, grpc_call_element *elem);
 
+  /* Implement grpc_channel_get_info() */
+  void (*get_channel_info)(grpc_exec_ctx *exec_ctx, grpc_channel_element *elem,
+                           const grpc_channel_info *channel_info);
+
   /* The name of this filter */
   const char *name;
 } grpc_channel_filter;
@@ -273,6 +277,10 @@ void grpc_channel_next_op(grpc_exec_ctx *exec_ctx, grpc_channel_element *elem,
                           grpc_transport_op *op);
 /* Pass through a request to get_peer to the next child element */
 char *grpc_call_next_get_peer(grpc_exec_ctx *exec_ctx, grpc_call_element *elem);
+/* Pass through a request to get_channel_info() to the next child element */
+void grpc_channel_next_get_info(grpc_exec_ctx *exec_ctx,
+                                grpc_channel_element *elem,
+                                const grpc_channel_info *channel_info);
 
 /* Given the top element of a channel stack, get the channel stack itself */
 grpc_channel_stack *grpc_channel_stack_from_top_element(
diff --git a/src/core/lib/channel/compress_filter.c b/src/core/lib/channel/compress_filter.c
index 294aa2fa18..2874d63fc7 100644
--- a/src/core/lib/channel/compress_filter.c
+++ b/src/core/lib/channel/compress_filter.c
@@ -332,4 +332,5 @@ const grpc_channel_filter grpc_compress_filter = {
     init_channel_elem,
     destroy_channel_elem,
     grpc_call_next_get_peer,
+    grpc_channel_next_get_info,
     "compress"};
diff --git a/src/core/lib/channel/connected_channel.c b/src/core/lib/channel/connected_channel.c
index 0e62d58475..038e819f72 100644
--- a/src/core/lib/channel/connected_channel.c
+++ b/src/core/lib/channel/connected_channel.c
@@ -134,6 +134,11 @@ static char *con_get_peer(grpc_exec_ctx *exec_ctx, grpc_call_element *elem) {
   return grpc_transport_get_peer(exec_ctx, chand->transport);
 }
 
+/* No-op. */
+static void con_get_channel_info(grpc_exec_ctx *exec_ctx,
+                                 grpc_channel_element *elem,
+                                 const grpc_channel_info *channel_info) {}
+
 static const grpc_channel_filter connected_channel_filter = {
     con_start_transport_stream_op,
     con_start_transport_op,
@@ -145,6 +150,7 @@ static const grpc_channel_filter connected_channel_filter = {
     init_channel_elem,
     destroy_channel_elem,
     con_get_peer,
+    con_get_channel_info,
     "connected",
 };
 
diff --git a/src/core/lib/channel/deadline_filter.c b/src/core/lib/channel/deadline_filter.c
index 449eb7b8d6..0e703d8d27 100644
--- a/src/core/lib/channel/deadline_filter.c
+++ b/src/core/lib/channel/deadline_filter.c
@@ -316,6 +316,7 @@ const grpc_channel_filter grpc_client_deadline_filter = {
     init_channel_elem,
     destroy_channel_elem,
     grpc_call_next_get_peer,
+    grpc_channel_next_get_info,
     "deadline",
 };
 
@@ -330,5 +331,6 @@ const grpc_channel_filter grpc_server_deadline_filter = {
     init_channel_elem,
     destroy_channel_elem,
     grpc_call_next_get_peer,
+    grpc_channel_next_get_info,
     "deadline",
 };
diff --git a/src/core/lib/channel/http_client_filter.c b/src/core/lib/channel/http_client_filter.c
index 0714f31bdd..f57d7c2453 100644
--- a/src/core/lib/channel/http_client_filter.c
+++ b/src/core/lib/channel/http_client_filter.c
@@ -448,4 +448,5 @@ const grpc_channel_filter grpc_http_client_filter = {
     init_channel_elem,
     destroy_channel_elem,
     grpc_call_next_get_peer,
+    grpc_channel_next_get_info,
     "http-client"};
diff --git a/src/core/lib/channel/http_server_filter.c b/src/core/lib/channel/http_server_filter.c
index 6f1a9f6349..6a33689fec 100644
--- a/src/core/lib/channel/http_server_filter.c
+++ b/src/core/lib/channel/http_server_filter.c
@@ -347,4 +347,5 @@ const grpc_channel_filter grpc_http_server_filter = {
     init_channel_elem,
     destroy_channel_elem,
     grpc_call_next_get_peer,
+    grpc_channel_next_get_info,
     "http-server"};
diff --git a/src/core/lib/channel/message_size_filter.c b/src/core/lib/channel/message_size_filter.c
index 85c307702f..1331fe1c65 100644
--- a/src/core/lib/channel/message_size_filter.c
+++ b/src/core/lib/channel/message_size_filter.c
@@ -248,4 +248,5 @@ const grpc_channel_filter grpc_message_size_filter = {
     init_channel_elem,
     destroy_channel_elem,
     grpc_call_next_get_peer,
+    grpc_channel_next_get_info,
     "message_size"};
diff --git a/src/core/lib/security/transport/client_auth_filter.c b/src/core/lib/security/transport/client_auth_filter.c
index cd4769ea10..053bf5972c 100644
--- a/src/core/lib/security/transport/client_auth_filter.c
+++ b/src/core/lib/security/transport/client_auth_filter.c
@@ -341,14 +341,8 @@ static void destroy_channel_elem(grpc_exec_ctx *exec_ctx,
   GRPC_AUTH_CONTEXT_UNREF(chand->auth_context, "client_auth_filter");
 }
 
-const grpc_channel_filter grpc_client_auth_filter = {auth_start_transport_op,
-                                                     grpc_channel_next_op,
-                                                     sizeof(call_data),
-                                                     init_call_elem,
-                                                     set_pollset_or_pollset_set,
-                                                     destroy_call_elem,
-                                                     sizeof(channel_data),
-                                                     init_channel_elem,
-                                                     destroy_channel_elem,
-                                                     grpc_call_next_get_peer,
-                                                     "client-auth"};
+const grpc_channel_filter grpc_client_auth_filter = {
+    auth_start_transport_op, grpc_channel_next_op,       sizeof(call_data),
+    init_call_elem,          set_pollset_or_pollset_set, destroy_call_elem,
+    sizeof(channel_data),    init_channel_elem,          destroy_channel_elem,
+    grpc_call_next_get_peer, grpc_channel_next_get_info, "client-auth"};
diff --git a/src/core/lib/security/transport/server_auth_filter.c b/src/core/lib/security/transport/server_auth_filter.c
index dd465be6f5..eaa1d0720b 100644
--- a/src/core/lib/security/transport/server_auth_filter.c
+++ b/src/core/lib/security/transport/server_auth_filter.c
@@ -278,4 +278,5 @@ const grpc_channel_filter grpc_server_auth_filter = {
     init_channel_elem,
     destroy_channel_elem,
     grpc_call_next_get_peer,
+    grpc_channel_next_get_info,
     "server-auth"};
diff --git a/src/core/lib/surface/channel.c b/src/core/lib/surface/channel.c
index 92d783b78d..1389df6886 100644
--- a/src/core/lib/surface/channel.c
+++ b/src/core/lib/surface/channel.c
@@ -175,6 +175,15 @@ char *grpc_channel_get_target(grpc_channel *channel) {
   return gpr_strdup(channel->target);
 }
 
+void grpc_channel_get_info(grpc_channel *channel,
+                           const grpc_channel_info *channel_info) {
+  grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
+  grpc_channel_element *elem =
+      grpc_channel_stack_element(CHANNEL_STACK_FROM_CHANNEL(channel), 0);
+  elem->filter->get_channel_info(&exec_ctx, elem, channel_info);
+  grpc_exec_ctx_finish(&exec_ctx);
+}
+
 static grpc_call *grpc_channel_create_call_internal(
     grpc_channel *channel, grpc_call *parent_call, uint32_t propagation_mask,
     grpc_completion_queue *cq, grpc_pollset_set *pollset_set_alternative,
diff --git a/src/core/lib/surface/lame_client.c b/src/core/lib/surface/lame_client.c
index d32c884e8e..d0df8e7e17 100644
--- a/src/core/lib/surface/lame_client.c
+++ b/src/core/lib/surface/lame_client.c
@@ -88,6 +88,10 @@ static char *lame_get_peer(grpc_exec_ctx *exec_ctx, grpc_call_element *elem) {
   return NULL;
 }
 
+static void lame_get_channel_info(grpc_exec_ctx *exec_ctx,
+                                  grpc_channel_element *elem,
+                                  const grpc_channel_info *channel_info) {}
+
 static void lame_start_transport_op(grpc_exec_ctx *exec_ctx,
                                     grpc_channel_element *elem,
                                     grpc_transport_op *op) {
@@ -140,6 +144,7 @@ const grpc_channel_filter grpc_lame_filter = {
     init_channel_elem,
     destroy_channel_elem,
     lame_get_peer,
+    lame_get_channel_info,
     "lame-client",
 };
 
diff --git a/src/core/lib/surface/server.c b/src/core/lib/surface/server.c
index 798f582cad..89dd825460 100644
--- a/src/core/lib/surface/server.c
+++ b/src/core/lib/surface/server.c
@@ -965,6 +965,7 @@ const grpc_channel_filter grpc_server_top_filter = {
     init_channel_elem,
     destroy_channel_elem,
     grpc_call_next_get_peer,
+    grpc_channel_next_get_info,
     "server",
 };
 
diff --git a/src/cpp/common/channel_filter.cc b/src/cpp/common/channel_filter.cc
index 25cd49cb7c..ad2c0f2295 100644
--- a/src/cpp/common/channel_filter.cc
+++ b/src/cpp/common/channel_filter.cc
@@ -57,6 +57,11 @@ void ChannelData::StartTransportOp(grpc_exec_ctx *exec_ctx,
   grpc_channel_next_op(exec_ctx, elem, op->op());
 }
 
+void ChannelData::GetInfo(grpc_exec_ctx *exec_ctx, grpc_channel_element *elem,
+                          const grpc_channel_info *channel_info) {
+  grpc_channel_next_get_info(exec_ctx, elem, channel_info);
+}
+
 // CallData
 
 void CallData::StartTransportStreamOp(grpc_exec_ctx *exec_ctx,
diff --git a/src/cpp/common/channel_filter.h b/src/cpp/common/channel_filter.h
index fc0deff3b3..e420efc71c 100644
--- a/src/cpp/common/channel_filter.h
+++ b/src/cpp/common/channel_filter.h
@@ -224,9 +224,13 @@ class ChannelData {
   const char *peer() const { return peer_; }
 
   // TODO(roth): Find a way to avoid passing elem into these methods.
+
   virtual void StartTransportOp(grpc_exec_ctx *exec_ctx,
                                 grpc_channel_element *elem, TransportOp *op);
 
+  virtual void GetInfo(grpc_exec_ctx *exec_ctx, grpc_channel_element *elem,
+                       const grpc_channel_info *channel_info);
+
  protected:
   /// Takes ownership of \a peer.
   ChannelData(const grpc_channel_args &args, const char *peer) : peer_(peer) {}
@@ -296,6 +300,13 @@ class ChannelFilter final {
     channel_data->StartTransportOp(exec_ctx, elem, &op_wrapper);
   }
 
+  static void GetChannelInfo(grpc_exec_ctx *exec_ctx,
+                             grpc_channel_element *elem,
+                             const grpc_channel_info *channel_info) {
+    ChannelDataType *channel_data = (ChannelDataType *)elem->channel_data;
+    channel_data->GetInfo(exec_ctx, elem, channel_info);
+  }
+
   static const size_t call_data_size = sizeof(CallDataType);
 
   static grpc_error *InitCallElement(grpc_exec_ctx *exec_ctx,
@@ -376,7 +387,8 @@ void RegisterChannelFilter(
        FilterType::call_data_size, FilterType::InitCallElement,
        FilterType::SetPollsetOrPollsetSet, FilterType::DestroyCallElement,
        FilterType::channel_data_size, FilterType::InitChannelElement,
-       FilterType::DestroyChannelElement, FilterType::GetPeer, name}};
+       FilterType::DestroyChannelElement, FilterType::GetPeer,
+       FilterType::GetChannelInfo, name}};
   internal::channel_filters->push_back(filter_record);
 }
 
diff --git a/src/ruby/ext/grpc/rb_grpc_imports.generated.c b/src/ruby/ext/grpc/rb_grpc_imports.generated.c
index f4546bf21f..e214216ece 100644
--- a/src/ruby/ext/grpc/rb_grpc_imports.generated.c
+++ b/src/ruby/ext/grpc/rb_grpc_imports.generated.c
@@ -110,6 +110,7 @@ grpc_call_get_peer_type grpc_call_get_peer_import;
 grpc_census_call_set_context_type grpc_census_call_set_context_import;
 grpc_census_call_get_context_type grpc_census_call_get_context_import;
 grpc_channel_get_target_type grpc_channel_get_target_import;
+grpc_channel_get_info_type grpc_channel_get_info_import;
 grpc_insecure_channel_create_type grpc_insecure_channel_create_import;
 grpc_lame_client_channel_create_type grpc_lame_client_channel_create_import;
 grpc_channel_destroy_type grpc_channel_destroy_import;
@@ -384,6 +385,7 @@ void grpc_rb_load_imports(HMODULE library) {
   grpc_census_call_set_context_import = (grpc_census_call_set_context_type) GetProcAddress(library, "grpc_census_call_set_context");
   grpc_census_call_get_context_import = (grpc_census_call_get_context_type) GetProcAddress(library, "grpc_census_call_get_context");
   grpc_channel_get_target_import = (grpc_channel_get_target_type) GetProcAddress(library, "grpc_channel_get_target");
+  grpc_channel_get_info_import = (grpc_channel_get_info_type) GetProcAddress(library, "grpc_channel_get_info");
   grpc_insecure_channel_create_import = (grpc_insecure_channel_create_type) GetProcAddress(library, "grpc_insecure_channel_create");
   grpc_lame_client_channel_create_import = (grpc_lame_client_channel_create_type) GetProcAddress(library, "grpc_lame_client_channel_create");
   grpc_channel_destroy_import = (grpc_channel_destroy_type) GetProcAddress(library, "grpc_channel_destroy");
diff --git a/src/ruby/ext/grpc/rb_grpc_imports.generated.h b/src/ruby/ext/grpc/rb_grpc_imports.generated.h
index f8467c4e7c..7a64c1431d 100644
--- a/src/ruby/ext/grpc/rb_grpc_imports.generated.h
+++ b/src/ruby/ext/grpc/rb_grpc_imports.generated.h
@@ -281,6 +281,9 @@ extern grpc_census_call_get_context_type grpc_census_call_get_context_import;
 typedef char *(*grpc_channel_get_target_type)(grpc_channel *channel);
 extern grpc_channel_get_target_type grpc_channel_get_target_import;
 #define grpc_channel_get_target grpc_channel_get_target_import
+typedef void(*grpc_channel_get_info_type)(grpc_channel *channel, const grpc_channel_info *channel_info);
+extern grpc_channel_get_info_type grpc_channel_get_info_import;
+#define grpc_channel_get_info grpc_channel_get_info_import
 typedef grpc_channel *(*grpc_insecure_channel_create_type)(const char *target, const grpc_channel_args *args, void *reserved);
 extern grpc_insecure_channel_create_type grpc_insecure_channel_create_import;
 #define grpc_insecure_channel_create grpc_insecure_channel_create_import