Read new env var to toggle

1 files changed, 14 insertions, 4 deletions

diff --git a/src/core/ext/transport/chttp2/transport/chttp2_transport.cc b/src/core/ext/transport/chttp2/transport/chttp2_transport.cc
index 768cee1190..f300ae9188 100644
--- a/src/core/ext/transport/chttp2/transport/chttp2_transport.cc
+++ b/src/core/ext/transport/chttp2/transport/chttp2_transport.cc
@@ -261,6 +261,9 @@ void grpc_chttp2_ref_transport(grpc_chttp2_transport* t) { gpr_ref(&t->refs); }
 
 static const grpc_transport_vtable* get_vtable(void);
 
+// -1 == unset, 0 == disabled, 1 == enabled
+static int flow_control_enabled = -1;
+
 static void init_transport(grpc_exec_ctx* exec_ctx, grpc_chttp2_transport* t,
                            const grpc_channel_args* channel_args,
                            grpc_endpoint* ep, bool is_client) {
@@ -544,12 +547,19 @@ static void init_transport(grpc_exec_ctx* exec_ctx, grpc_chttp2_transport* t,
     }
   }
 
-  if (true /* disable flow control*/) {
-    t->flow_control.Init<grpc_core::chttp2::TransportFlowControlDisabled>(t);
-    enable_bdp = false;
-  } else {
+  if (flow_control_enabled == -1) {
+    char* env_variable = gpr_getenv("GRPC_EXPERIMENTAL_DISABLE_FLOW_CONTROL");
+    if (env_variable != nullptr) flow_control_enabled = 0;
+    else flow_control_enabled = 1;
+    gpr_free(env_variable);
+  }
+
+  if (flow_control_enabled) {
     t->flow_control.Init<grpc_core::chttp2::TransportFlowControl>(exec_ctx, t,
                                                                   enable_bdp);
+  } else { 
+    t->flow_control.Init<grpc_core::chttp2::TransportFlowControlDisabled>(t);
+    enable_bdp = false;
   }
 
   /* No pings allowed before receiving a header or data frame. */