Restore checking initial request sent

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

@@ -377,6 +377,9 @@ typedef struct glb_lb_policy {
   /************************************************************/
   /*  client data associated with the LB server communication */
   /************************************************************/
+  /* Finished sending initial request. */
+  grpc_closure lb_on_sent_initial_request;
+
   /* Status from the LB server has been received. This signals the end of the LB
    * call. */
   grpc_closure lb_on_server_status_received;
@@ -416,6 +419,7 @@ typedef struct glb_lb_policy {
   /** LB fallback timer */
   grpc_timer lb_fallback_timer;
 
+  bool initial_request_sent;
   bool seen_initial_response;
 
   /* Stats for client-side load reporting. Should be unreffed and
@@ -1358,6 +1362,22 @@ static void client_load_report_done_locked(void* arg, grpc_error* error) {
   schedule_next_client_load_report(glb_policy);
 }
 
+static void do_send_client_load_report_locked(glb_lb_policy* glb_policy) {
+  grpc_op op;
+  memset(&op, 0, sizeof(op));
+  op.op = GRPC_OP_SEND_MESSAGE;
+  op.data.send_message.send_message = glb_policy->client_load_report_payload;
+  GRPC_CLOSURE_INIT(&glb_policy->client_load_report_closure,
+                    client_load_report_done_locked, glb_policy,
+                    grpc_combiner_scheduler(glb_policy->base.combiner));
+  grpc_call_error call_error = grpc_call_start_batch_and_execute(
+      glb_policy->lb_call, &op, 1, &glb_policy->client_load_report_closure);
+  if (call_error != GRPC_CALL_OK) {
+    gpr_log(GPR_ERROR, "[grpclb %p] call_error=%d", glb_policy, call_error);
+    GPR_ASSERT(GRPC_CALL_OK == call_error);
+  }
+}
+
 static bool load_report_counters_are_zero(grpc_grpclb_request* request) {
   grpc_grpclb_dropped_call_counts* drop_entries =
       (grpc_grpclb_dropped_call_counts*)
@@ -1401,22 +1421,15 @@ static void send_client_load_report_locked(void* arg, grpc_error* error) {
       grpc_raw_byte_buffer_create(&request_payload_slice, 1);
   grpc_slice_unref_internal(request_payload_slice);
   grpc_grpclb_request_destroy(request);
-  // Send load report message.
-  grpc_op op;
-  memset(&op, 0, sizeof(op));
-  op.op = GRPC_OP_SEND_MESSAGE;
-  op.data.send_message.send_message = glb_policy->client_load_report_payload;
-  GRPC_CLOSURE_INIT(&glb_policy->client_load_report_closure,
-                    client_load_report_done_locked, glb_policy,
-                    grpc_combiner_scheduler(glb_policy->base.combiner));
-  grpc_call_error call_error = grpc_call_start_batch_and_execute(
-      glb_policy->lb_call, &op, 1, &glb_policy->client_load_report_closure);
-  if (call_error != GRPC_CALL_OK) {
-    gpr_log(GPR_ERROR, "[grpclb %p] call_error=%d", glb_policy, call_error);
-    GPR_ASSERT(GRPC_CALL_OK == call_error);
+  // 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 lb_on_sent_initial_request_locked() below).
+  if (glb_policy->initial_request_sent) {
+    do_send_client_load_report_locked(glb_policy);
   }
 }
 
+static void lb_on_sent_initial_request_locked(void* arg, grpc_error* error);
 static void lb_on_server_status_received_locked(void* arg, grpc_error* error);
 static void lb_on_response_received_locked(void* arg, grpc_error* error);
 static void lb_call_init_locked(glb_lb_policy* glb_policy) {
@@ -1456,6 +1469,9 @@ static void lb_call_init_locked(glb_lb_policy* glb_policy) {
   grpc_slice_unref_internal(request_payload_slice);
   grpc_grpclb_request_destroy(request);
 
+  GRPC_CLOSURE_INIT(&glb_policy->lb_on_sent_initial_request,
+                    lb_on_sent_initial_request_locked, glb_policy,
+                    grpc_combiner_scheduler(glb_policy->base.combiner));
   GRPC_CLOSURE_INIT(&glb_policy->lb_on_server_status_received,
                     lb_on_server_status_received_locked, glb_policy,
                     grpc_combiner_scheduler(glb_policy->base.combiner));
@@ -1470,6 +1486,7 @@ static void lb_call_init_locked(glb_lb_policy* glb_policy) {
                     GRPC_GRPCLB_MIN_CONNECT_TIMEOUT_SECONDS * 1000,
                     GRPC_GRPCLB_RECONNECT_MAX_BACKOFF_SECONDS * 1000);
 
+  glb_policy->initial_request_sent = false;
   glb_policy->seen_initial_response = false;
   glb_policy->last_client_load_report_counters_were_zero = false;
 }
@@ -1528,8 +1545,13 @@ static void query_for_backends_locked(glb_lb_policy* glb_policy) {
   op->flags = 0;
   op->reserved = nullptr;
   op++;
-  call_error = grpc_call_start_batch_and_execute(glb_policy->lb_call, ops,
-                                                 (size_t)(op - ops), nullptr);
+  /* take a weak ref (won't prevent calling of \a glb_shutdown if the strong ref
+   * count goes to zero) to be unref'd in lb_on_sent_initial_request_locked() */
+  GRPC_LB_POLICY_WEAK_REF(&glb_policy->base,
+                          "lb_on_sent_initial_request_locked");
+  call_error = grpc_call_start_batch_and_execute(
+      glb_policy->lb_call, ops, (size_t)(op - ops),
+      &glb_policy->lb_on_sent_initial_request);
   GPR_ASSERT(GRPC_CALL_OK == call_error);
 
   op = ops;
@@ -1566,6 +1588,18 @@ static void query_for_backends_locked(glb_lb_policy* glb_policy) {
   GPR_ASSERT(GRPC_CALL_OK == call_error);
 }
 
+static void lb_on_sent_initial_request_locked(void* arg, grpc_error* error) {
+  glb_lb_policy* glb_policy = (glb_lb_policy*)arg;
+  glb_policy->initial_request_sent = true;
+  // If we attempted to send a client load report before the initial request was
+  // sent, send the load report now.
+  if (glb_policy->client_load_report_payload != nullptr) {
+    do_send_client_load_report_locked(glb_policy);
+  }
+  GRPC_LB_POLICY_WEAK_UNREF(&glb_policy->base,
+                            "lb_on_sent_initial_request_locked");
+}
+
 static void lb_on_response_received_locked(void* arg, grpc_error* error) {
   glb_lb_policy* glb_policy = (glb_lb_policy*)arg;
   grpc_op ops[2];