dynamic modules: SDK API does not expose extension_config values from DynamicModuleBootstrapExtension

[arminabf]

Description

The current implementation of the Dynamic Modules bootstrap extension envoy.bootstrap.dynamic_modulesenvoy.extensions.bootstrap.dynamic_modules.v3.DynamicModuleBootstrapExtension does not provide any API for dynamic modules to read values from the extension_config field at runtime. This makes it impossible to pass global configuration settings into dynamic modules through the standard bootstrap extension mechanism.

Background

The DynamicModuleBootstrapExtension proto supports an extension_config field of type google.protobuf.Any, which allows operators to embed arbitrary typed configuration alongside the module declaration.

For example:

bootstrap_extensions:
  - name: envoy.bootstrap.dynamic_modules
    typed_config:
      "@type": type.googleapis.com/envoy.extensions.bootstrap.dynamic_modules.v3.DynamicModuleBootstrapExtension
      dynamic_module_config:
        name: composer
      extension_name: composer
      extension_config:
        "@type": "type.googleapis.com/google.protobuf.StringValue"
        value: myCustomValue

Problem

Despite the extension_config field being present in the proto definition and accepted by Envoy during bootstrap parsing, there is no API surface exposed to the dynamic module itself to retrieve this value at runtime.

[kyessenov]

CC @mathetake

[mathetake]

i don't believe what you claimed here is true, otherwise it would be a SDK issue of Go or C++. at least it's available in Rust.

[mathetake]

cc @wbpcode

[wbpcode]

I guess it's wrong? Because when the ABI envoy_dynamic_module_on_bootstrap_extension_config_new is called, the second parameter is the serialized configuration?

For now, we only provide Rust SDK for the bootstrap dym. And you should could access the configuration at your declared init function?

[arminabf]

@wbpcode Thanks for the pointer to envoy_dynamic_module_on_bootstrap_extension_config_new – I did go down that path. The config value does arrive there correctly, but the issue is that wiring it up requires implementing the full set of ABI exports (envoy_dynamic_module_on_bootstrap_extension_new, _destroy, _config_destroy, _worker_thread_initialized, _drain_started, _shutdown, _server_initialized, and several more), all of which need to be present and exported from the Go module even if they do nothing. The result is a significant amount of boilerplate with non-obvious lifetime and pointer semantics that is hard to maintain and feels like it belongs in an SDK abstraction rather than in application code.

Is there any prospect of this being addressed in the Go SDK, or is bootstrap extension support in Go considered out of scope for now?

var dummyConfig C.int = 1

//export envoy_dynamic_module_on_bootstrap_extension_config_new
func envoy_dynamic_module_on_bootstrap_extension_config_new(
	extensionConfigEnvoyPtr C.envoy_dynamic_module_type_bootstrap_extension_config_envoy_ptr,
	name C.envoy_dynamic_module_type_envoy_buffer,
	config C.envoy_dynamic_module_type_envoy_buffer,
) C.envoy_dynamic_module_type_bootstrap_extension_config_module_ptr {
	myCustomValue := C.GoStringN((*C.char)(config.ptr), C.int(config.length))
	
        < ... process myCustomValue ... >

	// signal init complete, synchronously, since we have no async work
	C.envoy_dynamic_module_callback_bootstrap_extension_config_signal_init_complete(extensionConfigEnvoyPtr)
	return C.envoy_dynamic_module_type_bootstrap_extension_config_module_ptr(unsafe.Pointer(&dummyConfig))
}

//export envoy_dynamic_module_on_bootstrap_extension_new
func envoy_dynamic_module_on_bootstrap_extension_new(
	extensionConfigModulePtr C.envoy_dynamic_module_type_bootstrap_extension_config_module_ptr,
	extensionEnvoyPtr C.envoy_dynamic_module_type_bootstrap_extension_envoy_ptr,
) C.envoy_dynamic_module_type_bootstrap_extension_module_ptr {
	// we return the config pointer as the extension instance pointer
	return C.envoy_dynamic_module_type_bootstrap_extension_module_ptr(extensionConfigModulePtr)
}

//export envoy_dynamic_module_on_bootstrap_extension_destroy
func envoy_dynamic_module_on_bootstrap_extension_destroy(
	extensionModulePtr C.envoy_dynamic_module_type_bootstrap_extension_module_ptr,
) {
	// nothing to release
}

//export envoy_dynamic_module_on_bootstrap_extension_config_destroy
func envoy_dynamic_module_on_bootstrap_extension_config_destroy(
	extensionConfigModulePtr C.envoy_dynamic_module_type_bootstrap_extension_config_module_ptr,
) {
	// nothing to release
}

//export envoy_dynamic_module_on_bootstrap_extension_worker_thread_initialized
func envoy_dynamic_module_on_bootstrap_extension_worker_thread_initialized(
	extensionEnvoyPtr C.envoy_dynamic_module_type_bootstrap_extension_envoy_ptr,
	extensionModulePtr C.envoy_dynamic_module_type_bootstrap_extension_module_ptr,
) {
}

//export envoy_dynamic_module_on_bootstrap_extension_drain_started
func envoy_dynamic_module_on_bootstrap_extension_drain_started(
	extensionEnvoyPtr C.envoy_dynamic_module_type_bootstrap_extension_envoy_ptr,
	extensionModulePtr C.envoy_dynamic_module_type_bootstrap_extension_module_ptr,
) {
}

//export envoy_dynamic_module_on_bootstrap_extension_shutdown
func envoy_dynamic_module_on_bootstrap_extension_shutdown(
	extensionEnvoyPtr C.envoy_dynamic_module_type_bootstrap_extension_envoy_ptr,
	extensionModulePtr C.envoy_dynamic_module_type_bootstrap_extension_module_ptr,
	completionCallback C.envoy_dynamic_module_type_event_cb,
	completionContext unsafe.Pointer,
) {
}

//export envoy_dynamic_module_on_bootstrap_extension_server_initialized
func envoy_dynamic_module_on_bootstrap_extension_server_initialized(
	extensionEnvoyPtr C.envoy_dynamic_module_type_bootstrap_extension_envoy_ptr,
	extensionModulePtr C.envoy_dynamic_module_type_bootstrap_extension_module_ptr,
) {
}

//export envoy_dynamic_module_on_bootstrap_extension_config_scheduled
func envoy_dynamic_module_on_bootstrap_extension_config_scheduled(
	extensionConfigEnvoyPtr C.envoy_dynamic_module_type_bootstrap_extension_config_envoy_ptr,
	extensionConfigPtr C.envoy_dynamic_module_type_bootstrap_extension_config_module_ptr,
	eventID C.uint64_t,
) {
}

//export envoy_dynamic_module_on_bootstrap_extension_timer_fired
func envoy_dynamic_module_on_bootstrap_extension_timer_fired(
	extensionConfigEnvoyPtr C.envoy_dynamic_module_type_bootstrap_extension_config_envoy_ptr,
	extensionConfigModulePtr C.envoy_dynamic_module_type_bootstrap_extension_config_module_ptr,
	timerPtr C.envoy_dynamic_module_type_bootstrap_extension_timer_module_ptr,
) {
}

//export envoy_dynamic_module_on_bootstrap_extension_file_changed
func envoy_dynamic_module_on_bootstrap_extension_file_changed(
	extensionConfigEnvoyPtr C.envoy_dynamic_module_type_bootstrap_extension_config_envoy_ptr,
	extensionConfigModulePtr C.envoy_dynamic_module_type_bootstrap_extension_config_module_ptr,
	path C.envoy_dynamic_module_type_envoy_buffer,
	events C.uint32_t,
) {
}

//export envoy_dynamic_module_on_bootstrap_extension_cluster_add_or_update
func envoy_dynamic_module_on_bootstrap_extension_cluster_add_or_update(
	extensionConfigEnvoyPtr C.envoy_dynamic_module_type_bootstrap_extension_config_envoy_ptr,
	extensionConfigModulePtr C.envoy_dynamic_module_type_bootstrap_extension_config_module_ptr,
	clusterName C.envoy_dynamic_module_type_envoy_buffer,
) {
}

//export envoy_dynamic_module_on_bootstrap_extension_cluster_removal
func envoy_dynamic_module_on_bootstrap_extension_cluster_removal(
	extensionConfigEnvoyPtr C.envoy_dynamic_module_type_bootstrap_extension_config_envoy_ptr,
	extensionConfigModulePtr C.envoy_dynamic_module_type_bootstrap_extension_config_module_ptr,
	clusterName C.envoy_dynamic_module_type_envoy_buffer,
) {
}

//export envoy_dynamic_module_on_bootstrap_extension_listener_add_or_update
func envoy_dynamic_module_on_bootstrap_extension_listener_add_or_update(
	extensionConfigEnvoyPtr C.envoy_dynamic_module_type_bootstrap_extension_config_envoy_ptr,
	extensionConfigModulePtr C.envoy_dynamic_module_type_bootstrap_extension_config_module_ptr,
	listenerName C.envoy_dynamic_module_type_envoy_buffer,
) {
}

//export envoy_dynamic_module_on_bootstrap_extension_listener_removal
func envoy_dynamic_module_on_bootstrap_extension_listener_removal(
	extensionConfigEnvoyPtr C.envoy_dynamic_module_type_bootstrap_extension_config_envoy_ptr,
	extensionConfigModulePtr C.envoy_dynamic_module_type_bootstrap_extension_config_module_ptr,
	listenerName C.envoy_dynamic_module_type_envoy_buffer,
) {
}

//export envoy_dynamic_module_on_bootstrap_extension_http_callout_done
func envoy_dynamic_module_on_bootstrap_extension_http_callout_done(
	extensionConfigEnvoyPtr C.envoy_dynamic_module_type_bootstrap_extension_config_envoy_ptr,
	extensionConfigModulePtr C.envoy_dynamic_module_type_bootstrap_extension_config_module_ptr,
	calloutID C.uint64_t,
	result C.envoy_dynamic_module_type_http_callout_result,
	responseHeaders *C.envoy_dynamic_module_type_envoy_http_header,
	responseHeadersCount C.size_t,
	responseBody *C.envoy_dynamic_module_type_envoy_buffer,
	responseBodyCount C.size_t,
) {
}

//export envoy_dynamic_module_on_bootstrap_extension_admin_request
func envoy_dynamic_module_on_bootstrap_extension_admin_request(
	extensionConfigEnvoyPtr C.envoy_dynamic_module_type_bootstrap_extension_config_envoy_ptr,
	extensionConfigModulePtr C.envoy_dynamic_module_type_bootstrap_extension_config_module_ptr,
	path C.envoy_dynamic_module_type_envoy_buffer,
	params C.envoy_dynamic_module_type_envoy_buffer,
	responseBody C.envoy_dynamic_module_type_envoy_buffer, // Note: No pointer here
) C.uint32_t {
	return C.uint32_t(404)
}