Fix bug with proxy end2end test

src/core/ext/filters/client_channel/client_channel.cc

@@ -934,8 +934,10 @@ typedef struct client_channel_call_data {
   grpc_closure pick_closure;
   grpc_closure pick_cancel_closure;
 
+  // state needed to support channelz interception of recv trailing metadata.
   grpc_closure recv_trailing_metadata_ready_channelz;
   grpc_closure* original_recv_trailing_metadata;
+  grpc_transport_stream_op_batch* recv_trailing_metadata_batch;
 
   grpc_polling_entity* pollent;
   bool pollent_added_to_interested_parties;
@@ -1291,17 +1293,11 @@ static void recv_trailing_metadata_ready_channelz(void* arg,
             "error=%s",
             chand, calld, grpc_error_string(error));
   }
-  // find the right pending batch.
-  pending_batch* pending = pending_batch_find(
-      elem, "invoking recv_trailing_metadata_channelz for",
-      [](grpc_transport_stream_op_batch* batch) {
-        return batch->recv_trailing_metadata &&
-               batch->payload->recv_trailing_metadata
-                       .recv_trailing_metadata_ready != nullptr;
-      });
+  GPR_ASSERT(calld->recv_trailing_metadata_batch != nullptr);
   grpc_status_code status = GRPC_STATUS_OK;
   grpc_metadata_batch* md_batch =
-      pending->batch->payload->recv_trailing_metadata.recv_trailing_metadata;
+      calld->recv_trailing_metadata_batch->payload->recv_trailing_metadata
+          .recv_trailing_metadata;
   get_call_status(elem, md_batch, GRPC_ERROR_REF(error), &status, nullptr);
   grpc_core::channelz::SubchannelNode* channelz_subchannel =
       calld->pick.connected_subchannel->channelz_subchannel();
@@ -1311,29 +1307,39 @@ static void recv_trailing_metadata_ready_channelz(void* arg,
   } else {
     channelz_subchannel->RecordCallFailed();
   }
-  pending->batch = nullptr;
+  calld->recv_trailing_metadata_batch = nullptr;
   GRPC_CLOSURE_RUN(calld->original_recv_trailing_metadata, error);
 }
 
 // If channelz is enabled, intercept recv_trailing so that we may check the
 // status and associate it to a subchannel.
 // Returns true if callback was intercepted, false otherwise.
-static bool maybe_intercept_recv_trailing_for_channelz(
+static void maybe_intercept_recv_trailing_for_channelz(
     grpc_call_element* elem, grpc_transport_stream_op_batch* batch) {
   call_data* calld = static_cast<call_data*>(elem->call_data);
+  // only intercept payloads with recv trailing.
+  if (!batch->recv_trailing_metadata) {
+    return;
+  }
   // only add interceptor is channelz is enabled.
-  if (calld->pick.connected_subchannel->channelz_subchannel() != nullptr) {
-    GRPC_CLOSURE_INIT(&calld->recv_trailing_metadata_ready_channelz,
-                      recv_trailing_metadata_ready_channelz, elem,
-                      grpc_schedule_on_exec_ctx);
-    calld->original_recv_trailing_metadata =
-        batch->payload->recv_trailing_metadata.recv_trailing_metadata_ready;
-    batch->payload->recv_trailing_metadata.recv_trailing_metadata_ready =
-        &calld->recv_trailing_metadata_ready_channelz;
-    return true;
-  } else {
-    return false;
+  if (calld->pick.connected_subchannel->channelz_subchannel() == nullptr) {
+    return;
+  }
+  if (grpc_client_channel_trace.enabled()) {
+    gpr_log(GPR_INFO,
+            "calld=%p batch=%p: intercepting recv trailing for channelz", calld,
+            batch);
   }
+  GRPC_CLOSURE_INIT(&calld->recv_trailing_metadata_ready_channelz,
+                    recv_trailing_metadata_ready_channelz, elem,
+                    grpc_schedule_on_exec_ctx);
+  // save some state needed for the interception callback.
+  GPR_ASSERT(calld->recv_trailing_metadata_batch == nullptr);
+  calld->recv_trailing_metadata_batch = batch;
+  calld->original_recv_trailing_metadata =
+      batch->payload->recv_trailing_metadata.recv_trailing_metadata_ready;
+  batch->payload->recv_trailing_metadata.recv_trailing_metadata_ready =
+      &calld->recv_trailing_metadata_ready_channelz;
 }
 
 // This is called via the call combiner, so access to calld is synchronized.
@@ -1360,18 +1366,14 @@ static void pending_batches_resume(grpc_call_element* elem) {
     pending_batch* pending = &calld->pending_batches[i];
     grpc_transport_stream_op_batch* batch = pending->batch;
     if (batch != nullptr) {
-      bool intercepted =
-          maybe_intercept_recv_trailing_for_channelz(elem, batch);
+      maybe_intercept_recv_trailing_for_channelz(elem, batch);
       batch->handler_private.extra_arg = calld->subchannel_call;
       GRPC_CLOSURE_INIT(&batch->handler_private.closure,
                         resume_pending_batch_in_call_combiner, batch,
                         grpc_schedule_on_exec_ctx);
       closures.Add(&batch->handler_private.closure, GRPC_ERROR_NONE,
                    "pending_batches_resume");
-      // Only clear if we haven't intercepted anything.
-      if (!intercepted) {
-        pending_batch_clear(calld, pending);
-      }
+      pending_batch_clear(calld, pending);
     }
   }
   // Note: This will release the call combiner.