Add on_initiate callback for the send_ping tranport op

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

@@ -643,16 +643,22 @@ static void start_transport_op_locked(grpc_exec_ctx* exec_ctx, void* arg,
     op->connectivity_state = nullptr;
   }
 
-  if (op->send_ping != nullptr) {
+  if (op->send_ping.on_initiate != nullptr || op->send_ping.on_ack != nullptr) {
     if (chand->lb_policy == nullptr) {
       GRPC_CLOSURE_SCHED(
-          exec_ctx, op->send_ping,
+          exec_ctx, op->send_ping.on_initiate,
+          GRPC_ERROR_CREATE_FROM_STATIC_STRING("Ping with no load balancing"));
+      GRPC_CLOSURE_SCHED(
+          exec_ctx, op->send_ping.on_ack,
           GRPC_ERROR_CREATE_FROM_STATIC_STRING("Ping with no load balancing"));
     } else {
-      grpc_lb_policy_ping_one_locked(exec_ctx, chand->lb_policy, op->send_ping);
+      grpc_lb_policy_ping_one_locked(exec_ctx, chand->lb_policy,
+                                     op->send_ping.on_initiate,
+                                     op->send_ping.on_ack);
       op->bind_pollset = nullptr;
     }
-    op->send_ping = nullptr;
+    op->send_ping.on_initiate = nullptr;
+    op->send_ping.on_ack = nullptr;
   }
 
   if (op->disconnect_with_error != GRPC_ERROR_NONE) {

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

@@ -138,8 +138,9 @@ void grpc_lb_policy_exit_idle_locked(grpc_exec_ctx* exec_ctx,
 
 void grpc_lb_policy_ping_one_locked(grpc_exec_ctx* exec_ctx,
                                     grpc_lb_policy* policy,
-                                    grpc_closure* closure) {
+                                    grpc_closure* on_initiate,
-  policy->vtable->ping_one_locked(exec_ctx, policy, closure);
+                                    grpc_closure* on_ack) {
+  policy->vtable->ping_one_locked(exec_ctx, policy, on_initiate, on_ack);
 }
 
 void grpc_lb_policy_notify_on_state_change_locked(

src/core/ext/filters/client_channel/lb_policy.h

@@ -78,7 +78,7 @@ struct grpc_lb_policy_vtable {
 
   /** \see grpc_lb_policy_ping_one */
   void (*ping_one_locked)(grpc_exec_ctx* exec_ctx, grpc_lb_policy* policy,
-                          grpc_closure* closure);
+                          grpc_closure* on_initiate, grpc_closure* on_ack);
 
   /** Try to enter a READY connectivity state */
   void (*exit_idle_locked)(grpc_exec_ctx* exec_ctx, grpc_lb_policy* policy);
@@ -171,7 +171,8 @@ int grpc_lb_policy_pick_locked(grpc_exec_ctx* exec_ctx, grpc_lb_policy* policy,
     against one of the connected subchannels managed by \a policy. */
 void grpc_lb_policy_ping_one_locked(grpc_exec_ctx* exec_ctx,
                                     grpc_lb_policy* policy,
-                                    grpc_closure* closure);
+                                    grpc_closure* on_initiate,
+                                    grpc_closure* on_ack);
 
 /** Cancel picks for \a target.
     The \a on_complete callback of the pending picks will be invoked with \a

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

@@ -275,18 +275,17 @@ static void add_pending_pick(pending_pick** root,
 typedef struct pending_ping {
   struct pending_ping* next;
 
-  /* args for wrapped_notify */
+  /* args for sending the ping */
-  wrapped_rr_closure_arg wrapped_notify_arg;
+  grpc_closure* on_initiate;
+  grpc_closure* on_ack;
 } pending_ping;
 
-static void add_pending_ping(pending_ping** root, grpc_closure* notify) {
+static void add_pending_ping(pending_ping** root, grpc_closure* on_initiate,
+                             grpc_closure* on_ack) {
   pending_ping* pping = (pending_ping*)gpr_zalloc(sizeof(*pping));
-  pping->wrapped_notify_arg.wrapped_closure = notify;
+  pping->on_initiate = on_initiate;
-  pping->wrapped_notify_arg.free_when_done = pping;
+  pping->on_ack = on_ack;
   pping->next = *root;
-  GRPC_CLOSURE_INIT(&pping->wrapped_notify_arg.wrapper_closure,
-                    wrapped_rr_closure, &pping->wrapped_notify_arg,
-                    grpc_schedule_on_exec_ctx);
   *root = pping;
 }
 
@@ -822,14 +821,13 @@ static void create_rr_locked(grpc_exec_ctx* exec_ctx, glb_lb_policy* glb_policy,
   pending_ping* pping;
   while ((pping = glb_policy->pending_pings)) {
     glb_policy->pending_pings = pping->next;
-    GRPC_LB_POLICY_REF(glb_policy->rr_policy, "rr_handover_pending_ping");
-    pping->wrapped_notify_arg.rr_policy = glb_policy->rr_policy;
     if (grpc_lb_glb_trace.enabled()) {
       gpr_log(GPR_INFO, "[grpclb %p] Pending ping about to PING from RR %p",
               glb_policy, glb_policy->rr_policy);
     }
     grpc_lb_policy_ping_one_locked(exec_ctx, glb_policy->rr_policy,
-                                   &pping->wrapped_notify_arg.wrapper_closure);
+                                   pping->on_initiate, pping->on_ack);
+    gpr_free(pping);
   }
 }
 
@@ -1052,8 +1050,8 @@ static void glb_shutdown_locked(grpc_exec_ctx* exec_ctx, grpc_lb_policy* pol) {
 
   while (pping != nullptr) {
     pending_ping* next = pping->next;
-    GRPC_CLOSURE_SCHED(exec_ctx, &pping->wrapped_notify_arg.wrapper_closure,
+    GRPC_CLOSURE_SCHED(exec_ctx, pping->on_initiate, GRPC_ERROR_REF(error));
-                       GRPC_ERROR_REF(error));
+    GRPC_CLOSURE_SCHED(exec_ctx, pping->on_ack, GRPC_ERROR_REF(error));
     gpr_free(pping);
     pping = next;
   }
@@ -1251,12 +1249,14 @@ static grpc_connectivity_state glb_check_connectivity_locked(
 }
 
 static void glb_ping_one_locked(grpc_exec_ctx* exec_ctx, grpc_lb_policy* pol,
-                                grpc_closure* closure) {
+                                grpc_closure* on_initiate,
+                                grpc_closure* on_ack) {
   glb_lb_policy* glb_policy = (glb_lb_policy*)pol;
   if (glb_policy->rr_policy) {
-    grpc_lb_policy_ping_one_locked(exec_ctx, glb_policy->rr_policy, closure);
+    grpc_lb_policy_ping_one_locked(exec_ctx, glb_policy->rr_policy, on_initiate,
+                                   on_ack);
   } else {
-    add_pending_ping(&glb_policy->pending_pings, closure);
+    add_pending_ping(&glb_policy->pending_pings, on_initiate, on_ack);
     if (!glb_policy->started_picking) {
       start_picking_locked(exec_ctx, glb_policy);
     }

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

@@ -226,13 +226,16 @@ static void pf_notify_on_state_change_locked(grpc_exec_ctx* exec_ctx,
 }
 
 static void pf_ping_one_locked(grpc_exec_ctx* exec_ctx, grpc_lb_policy* pol,
-                               grpc_closure* closure) {
+                               grpc_closure* on_initiate,
+                               grpc_closure* on_ack) {
   pick_first_lb_policy* p = (pick_first_lb_policy*)pol;
   if (p->selected) {
     grpc_connected_subchannel_ping(exec_ctx, p->selected->connected_subchannel,
-                                   closure);
+                                   on_initiate, on_ack);
   } else {
-    GRPC_CLOSURE_SCHED(exec_ctx, closure,
+    GRPC_CLOSURE_SCHED(exec_ctx, on_initiate,
+                       GRPC_ERROR_CREATE_FROM_STATIC_STRING("Not connected"));
+    GRPC_CLOSURE_SCHED(exec_ctx, on_ack,
                        GRPC_ERROR_CREATE_FROM_STATIC_STRING("Not connected"));
   }
 }

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

@@ -548,7 +548,8 @@ static void rr_notify_on_state_change_locked(grpc_exec_ctx* exec_ctx,
 }
 
 static void rr_ping_one_locked(grpc_exec_ctx* exec_ctx, grpc_lb_policy* pol,
-                               grpc_closure* closure) {
+                               grpc_closure* on_initiate,
+                               grpc_closure* on_ack) {
   round_robin_lb_policy* p = (round_robin_lb_policy*)pol;
   const size_t next_ready_index = get_next_ready_subchannel_index_locked(p);
   if (next_ready_index < p->subchannel_list->num_subchannels) {
@@ -556,11 +557,14 @@ static void rr_ping_one_locked(grpc_exec_ctx* exec_ctx, grpc_lb_policy* pol,
         &p->subchannel_list->subchannels[next_ready_index];
     grpc_connected_subchannel* target = GRPC_CONNECTED_SUBCHANNEL_REF(
         selected->connected_subchannel, "rr_ping");
-    grpc_connected_subchannel_ping(exec_ctx, target, closure);
+    grpc_connected_subchannel_ping(exec_ctx, target, on_initiate, on_ack);
     GRPC_CONNECTED_SUBCHANNEL_UNREF(exec_ctx, target, "rr_ping");
   } else {
     GRPC_CLOSURE_SCHED(
-        exec_ctx, closure,
+        exec_ctx, on_initiate,
+        GRPC_ERROR_CREATE_FROM_STATIC_STRING("Round Robin not connected"));
+    GRPC_CLOSURE_SCHED(
+        exec_ctx, on_ack,
         GRPC_ERROR_CREATE_FROM_STATIC_STRING("Round Robin not connected"));
   }
 }

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

@@ -584,10 +584,12 @@ void grpc_connected_subchannel_notify_on_state_change(
 
 void grpc_connected_subchannel_ping(grpc_exec_ctx* exec_ctx,
                                     grpc_connected_subchannel* con,
-                                    grpc_closure* closure) {
+                                    grpc_closure* on_initiate,
+                                    grpc_closure* on_ack) {
   grpc_transport_op* op = grpc_make_transport_op(nullptr);
   grpc_channel_element* elem;
-  op->send_ping = closure;
+  op->send_ping.on_initiate = on_initiate;
+  op->send_ping.on_ack = on_ack;
   elem = grpc_channel_stack_element(CHANNEL_STACK_FROM_CONNECTION(con), 0);
   elem->filter->start_transport_op(exec_ctx, elem, op);
 }

src/core/ext/filters/client_channel/subchannel.h

@@ -135,7 +135,8 @@ void grpc_connected_subchannel_notify_on_state_change(
     grpc_closure* notify);
 void grpc_connected_subchannel_ping(grpc_exec_ctx* exec_ctx,
                                     grpc_connected_subchannel* channel,
-                                    grpc_closure* notify);
+                                    grpc_closure* on_initiate,
+                                    grpc_closure* on_ack);
 
 /** retrieve the grpc_connected_subchannel - or NULL if called before
     the subchannel becomes connected */

src/core/ext/transport/chttp2/transport/chttp2_transport.cc

@@ -1815,8 +1815,9 @@ static void perform_transport_op_locked(grpc_exec_ctx* exec_ctx,
     grpc_endpoint_add_to_pollset_set(exec_ctx, t->ep, op->bind_pollset_set);
   }
 
-  if (op->send_ping) {
+  if (op->send_ping.on_initiate != nullptr || op->send_ping.on_ack != nullptr) {
-    send_ping_locked(exec_ctx, t, nullptr, op->send_ping);
+    send_ping_locked(exec_ctx, t, op->send_ping.on_initiate,
+                     op->send_ping.on_ack);
     grpc_chttp2_initiate_write(exec_ctx, t,
                                GRPC_CHTTP2_INITIATE_WRITE_APPLICATION_PING);
   }

src/core/lib/surface/channel_ping.cc

@@ -57,7 +57,7 @@ void grpc_channel_ping(grpc_channel* channel, grpc_completion_queue* cq,
   pr->tag = tag;
   pr->cq = cq;
   GRPC_CLOSURE_INIT(&pr->closure, ping_done, pr, grpc_schedule_on_exec_ctx);
-  op->send_ping = &pr->closure;
+  op->send_ping.on_ack = &pr->closure;
   op->bind_pollset = grpc_cq_pollset(cq);
   GPR_ASSERT(grpc_cq_begin_op(cq, tag));
   top_elem->filter->start_transport_op(&exec_ctx, top_elem, op);

src/core/lib/surface/lame_client.cc

@@ -104,9 +104,14 @@ static void lame_start_transport_op(grpc_exec_ctx* exec_ctx,
     GRPC_CLOSURE_SCHED(exec_ctx, op->on_connectivity_state_change,
                        GRPC_ERROR_NONE);
   }
-  if (op->send_ping != nullptr) {
+  if (op->send_ping.on_initiate != nullptr) {
     GRPC_CLOSURE_SCHED(
-        exec_ctx, op->send_ping,
+        exec_ctx, op->send_ping.on_initiate,
+        GRPC_ERROR_CREATE_FROM_STATIC_STRING("lame client channel"));
+  }
+  if (op->send_ping.on_ack != nullptr) {
+    GRPC_CLOSURE_SCHED(
+        exec_ctx, op->send_ping.on_ack,
         GRPC_ERROR_CREATE_FROM_STATIC_STRING("lame client channel"));
   }
   GRPC_ERROR_UNREF(op->disconnect_with_error);

src/core/lib/transport/transport.h

@@ -245,8 +245,14 @@ typedef struct grpc_transport_op {
   grpc_pollset* bind_pollset;
   /** add this transport to a pollset_set */
   grpc_pollset_set* bind_pollset_set;
-  /** send a ping, call this back if not NULL */
+  /** send a ping, if either on_initiate or on_ack is not NULL */
-  grpc_closure* send_ping;
+  struct {
+    /** Ping may be delayed by the transport, on_initiate callback will be
+        called when the ping is actually being sent. */
+    grpc_closure* on_initiate;
+    /** Called when the ping ack is received */
+    grpc_closure* on_ack;
+  } send_ping;
 
   /***************************************************************************
    * remaining fields are initialized and used at the discretion of the

src/core/lib/transport/transport_op_string.cc

@@ -187,7 +187,7 @@ char* grpc_transport_op_string(grpc_transport_op* op) {
     gpr_strvec_add(&b, gpr_strdup("BIND_POLLSET_SET"));
   }
 
-  if (op->send_ping != nullptr) {
+  if (op->send_ping.on_initiate != nullptr || op->send_ping.on_ack != nullptr) {
     if (!first) gpr_strvec_add(&b, gpr_strdup(" "));
     // first = false;
     gpr_strvec_add(&b, gpr_strdup("SEND_PING"));