sketching minimal stack configurator

include/grpc/impl/codegen/grpc_types.h

@@ -152,6 +152,9 @@ typedef struct {
 #define GRPC_ARG_ENABLE_CENSUS "grpc.census"
 /** If non-zero, enable load reporting. */
 #define GRPC_ARG_ENABLE_LOAD_REPORTING "grpc.loadreporting"
+/** Request that optional features default to off (regardless of what they
+    usually default to) - to enable tight control over what gets enabled */
+#define GRPC_ARG_MINIMAL_STACK "grpc.minimal_stack"
 /** Maximum number of concurrent incoming streams to allow on a http2
     connection. Int valued. */
 #define GRPC_ARG_MAX_CONCURRENT_STREAMS "grpc.max_concurrent_streams"

src/core/ext/census/grpc_plugin.c

@@ -48,7 +48,7 @@ static bool is_census_enabled(const grpc_channel_args *a) {
       return a->args[i].value.integer != 0 && census_enabled();
     }
   }
-  return census_enabled();
+  return census_enabled() && !grpc_channel_args_want_minimal_stack(a);
 }
 
 static bool maybe_add_census_filter(grpc_exec_ctx *exec_ctx,

src/core/lib/channel/channel_args.c

@@ -346,3 +346,10 @@ int grpc_channel_arg_get_integer(grpc_arg *arg, grpc_integer_options options) {
   }
   return arg->value.integer;
 }
+
+bool grpc_channel_args_want_minimal_stack(const grpc_channel_args *args) {
+  const grpc_arg *arg = grpc_channel_args_find(args, GRPC_ARG_MINIMAL_STACK);
+  if (arg == NULL) return false;
+  if (arg->type == GRPC_ARG_INTEGER && arg->value.integer == 0) return false;
+  return true;
+}

src/core/lib/channel/channel_args.h

@@ -113,6 +113,8 @@ grpc_channel_args *grpc_channel_args_set_socket_mutator(
 const grpc_arg *grpc_channel_args_find(const grpc_channel_args *args,
                                        const char *name);
 
+bool grpc_channel_args_want_minimal_stack(const grpc_channel_args *args);
+
 typedef struct grpc_integer_options {
   int default_value;  // Return this if value is outside of expected bounds.
   int min_value;

src/core/lib/surface/init.c

@@ -107,6 +107,22 @@ static bool maybe_add_http_filter(grpc_exec_ctx *exec_ctx,
   return true;
 }
 
+typedef struct {
+  const grpc_channel_filter *filter;
+  const char *controlling_channel_arg;
+  bool default_on;
+} maybe_prepend_filter_args;
+
+static const maybe_prepend_filter_args message_size_args = {
+    &grpc_message_size_filter, NULL, true};
+
+static bool maybe_prepend_filter(grpc_exec_ctx *exec_ctx,
+                                 grpc_channel_stack_builder *builder,
+                                 void *arg) {
+  return grpc_channel_stack_builder_prepend_filter(
+      builder, (const grpc_channel_filter *)arg, NULL, NULL);
+}
+
 static void register_builtin_channel_init() {
   grpc_channel_init_register_stage(
       GRPC_CLIENT_DIRECT_CHANNEL, GRPC_CHANNEL_INIT_BUILTIN_PRIORITY,
@@ -119,7 +135,7 @@ static void register_builtin_channel_init() {
       (void *)&grpc_max_age_filter);
   grpc_channel_init_register_stage(
       GRPC_CLIENT_SUBCHANNEL, GRPC_CHANNEL_INIT_BUILTIN_PRIORITY,
-      prepend_filter, (void *)&grpc_message_size_filter);
+      maybe_prepend_filter, (void *)&message_size_args);
   grpc_channel_init_register_stage(
       GRPC_CLIENT_DIRECT_CHANNEL, GRPC_CHANNEL_INIT_BUILTIN_PRIORITY,
       prepend_filter, (void *)&grpc_message_size_filter);