Intercept trailing in subchannel, not client_channel

1 files changed, 70 insertions, 0 deletions

diff --git a/src/core/ext/filters/client_channel/subchannel.cc b/src/core/ext/filters/client_channel/subchannel.cc
index 4a668b0fa7..38d7a5a6e3 100644
--- a/src/core/ext/filters/client_channel/subchannel.cc
+++ b/src/core/ext/filters/client_channel/subchannel.cc
@@ -49,6 +49,8 @@
 #include "src/core/lib/surface/channel.h"
 #include "src/core/lib/surface/channel_init.h"
 #include "src/core/lib/transport/connectivity_state.h"
+#include "src/core/lib/transport/error_utils.h"
+#include "src/core/lib/transport/status_metadata.h"
 
 #define INTERNAL_REF_BITS 16
 #define STRONG_REF_MASK (~(gpr_atm)((1 << INTERNAL_REF_BITS) - 1))
@@ -144,6 +146,11 @@ struct grpc_subchannel {
 struct grpc_subchannel_call {
   grpc_core::ConnectedSubchannel* connection;
   grpc_closure* schedule_closure_after_destroy;
+  // state needed to support channelz interception of recv trailing metadata.
+  grpc_closure recv_trailing_metadata_ready_channelz;
+  grpc_closure* original_recv_trailing_metadata;
+  grpc_metadata_batch* recv_trailing_metadata;
+  grpc_millis deadline;
 };
 
 #define SUBCHANNEL_CALL_TO_CALL_STACK(call)                          \
@@ -745,12 +752,74 @@ void grpc_subchannel_call_unref(
   GRPC_CALL_STACK_UNREF(SUBCHANNEL_CALL_TO_CALL_STACK(c), REF_REASON);
 }
 
+// Sets *status and *server_pushback_md based on md_batch and error.
+// Only sets *server_pushback_md if server_pushback_md != nullptr.
+static void get_call_status(grpc_subchannel_call* call,
+                            grpc_metadata_batch* md_batch, grpc_error* error,
+                            grpc_status_code* status) {
+  if (error != GRPC_ERROR_NONE) {
+    grpc_error_get_status(error, call->deadline, status, nullptr, nullptr,
+                          nullptr);
+  } else {
+    GPR_ASSERT(md_batch->idx.named.grpc_status != nullptr);
+    *status =
+        grpc_get_status_code_from_metadata(md_batch->idx.named.grpc_status->md);
+  }
+  GRPC_ERROR_UNREF(error);
+}
+
+static void recv_trailing_metadata_ready_channelz(void* arg,
+                                                  grpc_error* error) {
+  grpc_subchannel_call* call = static_cast<grpc_subchannel_call*>(arg);
+  GPR_ASSERT(call->recv_trailing_metadata != nullptr);
+  grpc_status_code status = GRPC_STATUS_OK;
+  grpc_metadata_batch* md_batch = call->recv_trailing_metadata;
+  get_call_status(call, md_batch, GRPC_ERROR_REF(error), &status);
+  grpc_core::channelz::SubchannelNode* channelz_subchannel =
+      call->connection->channelz_subchannel();
+  GPR_ASSERT(channelz_subchannel != nullptr);
+  if (status == GRPC_STATUS_OK) {
+    channelz_subchannel->RecordCallSucceeded();
+  } else {
+    channelz_subchannel->RecordCallFailed();
+  }
+  call->recv_trailing_metadata = nullptr;
+  GRPC_CLOSURE_RUN(call->original_recv_trailing_metadata,
+                   GRPC_ERROR_REF(error));
+}
+
+// If channelz is enabled, intercept recv_trailing so that we may check the
+// status and associate it to a subchannel.
+static void maybe_intercept_recv_trailing_metadata_for_channelz(
+    grpc_subchannel_call* call, grpc_transport_stream_op_batch* batch) {
+  // only intercept payloads with recv trailing.
+  if (!batch->recv_trailing_metadata) {
+    return;
+  }
+  // only add interceptor is channelz is enabled.
+  if (call->connection->channelz_subchannel() == nullptr) {
+    return;
+  }
+  GRPC_CLOSURE_INIT(&call->recv_trailing_metadata_ready_channelz,
+                    recv_trailing_metadata_ready_channelz, call,
+                    grpc_schedule_on_exec_ctx);
+  // save some state needed for the interception callback.
+  GPR_ASSERT(call->recv_trailing_metadata == nullptr);
+  call->recv_trailing_metadata =
+      batch->payload->recv_trailing_metadata.recv_trailing_metadata;
+  call->original_recv_trailing_metadata =
+      batch->payload->recv_trailing_metadata.recv_trailing_metadata_ready;
+  batch->payload->recv_trailing_metadata.recv_trailing_metadata_ready =
+      &call->recv_trailing_metadata_ready_channelz;
+}
+
 void grpc_subchannel_call_process_op(grpc_subchannel_call* call,
                                      grpc_transport_stream_op_batch* batch) {
   GPR_TIMER_SCOPE("grpc_subchannel_call_process_op", 0);
   grpc_call_stack* call_stack = SUBCHANNEL_CALL_TO_CALL_STACK(call);
   grpc_call_element* top_elem = grpc_call_stack_element(call_stack, 0);
   GRPC_CALL_LOG_OP(GPR_INFO, top_elem, batch);
+  maybe_intercept_recv_trailing_metadata_for_channelz(call, batch);
   top_elem->filter->start_transport_stream_op_batch(top_elem, batch);
 }
 
@@ -872,6 +941,7 @@ grpc_error* ConnectedSubchannel::CreateCall(const CallArgs& args,
       Ref(DEBUG_LOCATION, "subchannel_call");
   connection.release();  // Ref is passed to the grpc_subchannel_call object.
   (*call)->connection = this;
+  (*call)->deadline = args.deadline;
   const grpc_call_element_args call_args = {
       callstk,           /* call_stack */
       nullptr,           /* server_transport_data */