Merge pull request #574 from tsloughter/sdk-disabled

add support for OTEL_SDK_DISABLED environment variable

CHANGELOG.md

@@ -9,6 +9,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## SDK
 
+### Added
+
+- [Add support for OTEL_SDK_DISABLED environment variable and sdk_disabled
+  application environment
+  variable](https://github.com/open-telemetry/opentelemetry-erlang/pull/574)
+
 ### Changes
 
 - [Resource is now an argument to TracerProvider start, but still set

apps/opentelemetry/src/opentelemetry_app.erl

@@ -26,25 +26,32 @@
 
 start(_StartType, _StartArgs) ->
     Config = otel_configuration:merge_with_os(
-             application:get_all_env(opentelemetry)),
-
-    %% set global span limits record based on configuration
-    otel_span_limits:set(Config),
+               application:get_all_env(opentelemetry)),
 
     %% set the global propagators for HTTP based on the application env
+    %% these get set even if the SDK is disabled
     setup_text_map_propagators(Config),
 
     SupResult = opentelemetry_sup:start_link(Config),
 
-    Resource = otel_resource_detector:get_resource(),
-    _ = otel_tracer_provider_sup:start(?GLOBAL_TRACER_PROVIDER_NAME, Resource, Config),
+    case Config of
+        #{sdk_disabled := true} ->
+            %% skip the rest if the SDK is disabled
+            SupResult;
+        _ ->
+            %% set global span limits record based on configuration
+            otel_span_limits:set(Config),
+
+            Resource = otel_resource_detector:get_resource(),
+            _ = otel_tracer_provider_sup:start(?GLOBAL_TRACER_PROVIDER_NAME, Resource, Config),
 
-    %% must be done after the supervisor starts so that otel_tracer_server is running
-    %% TODO: make this work with release upgrades. Currently if an application's version
-    %% changes the version in the tracer will not be updated.
-    create_loaded_application_tracers(Config),
+            %% must be done after the supervisor starts so that otel_tracer_server is running
+            %% TODO: make this work with release upgrades. Currently if an application's version
+            %% changes the version in the tracer will not be updated.
+            create_loaded_application_tracers(Config),
 
-    SupResult.
+            SupResult
+    end.
 
 stop(_State) ->
     ok.

apps/opentelemetry/src/opentelemetry_sup.erl

@@ -30,6 +30,8 @@
 start_link(Opts) ->
     supervisor:start_link({local, ?SERVER}, ?MODULE, [Opts]).
 
+init([#{sdk_disabled := true}]) ->
+    {ok, {#{}, []}};
 init([Opts]) ->
     SupFlags = #{strategy => one_for_one,
                  intensity => 1,

apps/opentelemetry/src/otel_configuration.erl

@@ -32,7 +32,8 @@
 
 %% required configuration
 %% using a map instead of a record because there can be more values
--type t() :: #{log_level := atom(),
+-type t() :: #{sdk_disabled := boolean(),
+               log_level := atom(),
                register_loaded_applications := boolean() | undefined,
                create_application_tracers := boolean() | undefined,
                id_generator := module(),
@@ -70,7 +71,8 @@
 
 -spec new() -> t().
 new() ->
-    ?assert_type(#{log_level => info,
+    ?assert_type(#{sdk_disabled => false,
+                   log_level => info,
                    register_loaded_applications => undefined,
                    create_application_tracers => undefined,
                    id_generator => otel_id_generator,
@@ -295,7 +297,8 @@ report_cb(#{source := transform,
      [OSVar, Key, Transform, Value, otel_utils:format_exception(Kind, Reason, StackTrace)]}.
 
 config_mappings(general_sdk) ->
-    [{"OTEL_LOG_LEVEL", log_level, existing_atom},
+    [{"OTEL_SDK_DISABLED", sdk_disabled, boolean},
+     {"OTEL_LOG_LEVEL", log_level, existing_atom},
 
      %% `register_loaded_applications' is kept for backwards compatibility
      {"OTEL_REGISTER_LOADED_APPLICATIONS", register_loaded_applications, boolean},

apps/opentelemetry/src/otel_resource_detector.erl

@@ -58,7 +58,7 @@ get_resource() ->
 get_resource(Timeout) ->
     try gen_statem:call(?MODULE, get_resource, Timeout)
     catch
-        exit:{timeout, _} ->
+        _:_ ->
             %% TODO: should we return an error instead?
             %% returning an empty resource ensures we continue on and
             %% don't crash anything depending on the returned resource

apps/opentelemetry/src/otel_tracer_provider_sup.erl

@@ -35,7 +35,13 @@ start(Name, Config) ->
     start(Name, otel_resource:create([]), Config).
 
 start(Name, Resource, Config) ->
-    supervisor:start_child(?MODULE, [Name, Resource, Config]).
+    try
+        supervisor:start_child(?MODULE, [Name, Resource, Config])
+    catch
+        exit:{noproc, _} ->
+            %% no tracer provider sup is started, the sdk is probably disabled
+            {error, no_tracer_provider_supervisor}
+    end.
 
 init([]) ->
     SupFlags = #{strategy => simple_one_for_one,

apps/opentelemetry/test/opentelemetry_SUITE.erl

@@ -33,7 +33,7 @@ all() ->
      {group, otel_batch_processor}].
 
 all_cases() ->
-    [with_span, macros, child_spans,
+    [with_span, macros, child_spans, disabled_sdk,
      update_span_data, tracer_instrumentation_scope, tracer_previous_ctx, stop_temporary_app,
      reset_after, attach_ctx, default_sampler, non_recording_ets_table,
      root_span_sampling_always_on, root_span_sampling_always_off,
@@ -59,6 +59,10 @@ init_per_group(Processor, Config) ->
 end_per_group(_, _Config) ->
     ok.
 
+init_per_testcase(disabled_sdk, Config) ->
+    application:set_env(opentelemetry, sdk_disabled, true),
+    {ok, _} = application:ensure_all_started(opentelemetry),
+    Config;
 init_per_testcase(no_exporter, Config) ->
     application:set_env(opentelemetry, processors,
                         [{otel_batch_processor, #{scheduled_delay_ms => 1}}]),
@@ -139,6 +143,11 @@ init_per_testcase(_, Config) ->
     {ok, _} = application:ensure_all_started(opentelemetry),
     [{tid, Tid} | Config].
 
+end_per_testcase(disabled_sdk, _Config) ->
+    application:set_env(opentelemetry, sdk_disabled, false),
+    _ = application:stop(opentelemetry),
+    _ = application:unload(opentelemetry),
+    ok;
 end_per_testcase(disable_auto_creation, _Config) ->
     _ = application:stop(opentelemetry),
     _ = application:unload(opentelemetry),
@@ -1062,6 +1071,13 @@ too_many_attributes(Config) ->
 
     ok.
 
+disabled_sdk(_Config) ->
+    SpanCtx1 = ?start_span(<<"span-1">>),
+
+    ?assertMatch(#span_ctx{trace_id=0,
+                           span_id=0}, SpanCtx1),
+    ok.
+
 no_exporter(_Config) ->
     SpanCtx1 = ?start_span(<<"span-1">>),