Add tracing for connect latency

src/core/iomgr/tcp_client_posix.c

@@ -54,6 +54,8 @@
 #include <grpc/support/string_util.h>
 #include <grpc/support/time.h>
 
+extern int grpc_tcp_trace;
+
 typedef struct {
   void (*cb)(void *arg, grpc_endpoint *tcp);
   void *cb_arg;
@@ -92,6 +94,10 @@ error:
 static void tc_on_alarm(void *acp, int success) {
   int done;
   async_connect *ac = acp;
+  if (grpc_tcp_trace) {
+    gpr_log(GPR_DEBUG, "CLIENT_CONNECT: %s: on_alarm: success=%d", ac->addr_str,
+            success);
+  }
   gpr_mu_lock(&ac->mu);
   if (ac->fd != NULL) {
     grpc_fd_shutdown(ac->fd);
@@ -116,6 +122,11 @@ static void on_writable(void *acp, int success) {
   void *cb_arg = ac->cb_arg;
   grpc_fd *fd;
 
+  if (grpc_tcp_trace) {
+    gpr_log(GPR_DEBUG, "CLIENT_CONNECT: %s: on_writable: success=%d",
+            ac->addr_str, success);
+  }
+
   gpr_mu_lock(&ac->mu);
   GPR_ASSERT(ac->fd);
   fd = ac->fd;
@@ -264,6 +275,11 @@ void grpc_tcp_client_connect(void (*cb)(void *arg, grpc_endpoint *ep),
   ac->write_closure.cb = on_writable;
   ac->write_closure.cb_arg = ac;
 
+  if (grpc_tcp_trace) {
+    gpr_log(GPR_DEBUG, "CLIENT_CONNECT: %s: asynchronously connecting",
+            ac->addr_str);
+  }
+
   gpr_mu_lock(&ac->mu);
   grpc_alarm_init(&ac->alarm,
                   gpr_convert_clock_type(deadline, GPR_CLOCK_MONOTONIC),