Update env var documentation

doc/environment_variables.md

@@ -50,6 +50,7 @@ some configuration as environment variables that can be set.
   - channel_stack_builder - traces information about channel stacks being built
   - executor - traces grpc's internal thread pool ('the executor')
   - http - traces state in the http2 transport engine
+  - http2_stream_state - traces all http2 stream state mutations.
   - http1 - traces HTTP/1.x operations performed by gRPC
   - inproc - traces the in-process transport
   - flowctl - traces http2 flow control

src/core/ext/transport/chttp2/transport/stream_lists.c

@@ -66,8 +66,8 @@ static bool stream_list_pop(grpc_chttp2_transport *t,
   }
   *stream = s;
   if (s && GRPC_TRACER_ON(grpc_trace_http2_stream_state)) {
-    gpr_log(GPR_DEBUG, "t[%p]: pop stream %d from %s", t, s->id,
-            stream_list_id_string(id));
+    gpr_log(GPR_DEBUG, "%p[%d][%s]: pop from %s", t, s->id,
+            t->is_client ? "cli" : "svr", stream_list_id_string(id));
   }
   return s != 0;
 }
@@ -88,8 +88,8 @@ static void stream_list_remove(grpc_chttp2_transport *t, grpc_chttp2_stream *s,
     t->lists[id].tail = s->links[id].prev;
   }
   if (GRPC_TRACER_ON(grpc_trace_http2_stream_state)) {
-    gpr_log(GPR_DEBUG, "t[%p]: remove stream %d from %s", t, s->id,
-            stream_list_id_string(id));
+    gpr_log(GPR_DEBUG, "%p[%d][%s]: remove from %s", t, s->id,
+            t->is_client ? "cli" : "svr", stream_list_id_string(id));
   }
 }
 
@@ -120,8 +120,8 @@ static void stream_list_add_tail(grpc_chttp2_transport *t,
   t->lists[id].tail = s;
   s->included[id] = 1;
   if (GRPC_TRACER_ON(grpc_trace_http2_stream_state)) {
-    gpr_log(GPR_DEBUG, "t[%p]: add stream %d from %s", t, s->id,
-            stream_list_id_string(id));
+    gpr_log(GPR_DEBUG, "%p[%d][%s]: add to %s", t, s->id,
+            t->is_client ? "cli" : "svr", stream_list_id_string(id));
   }
 }