Merge pull request #4 from tsloughter/otep-66

separate context propagation otep

src/opentelemetry.erl

@@ -29,8 +29,14 @@
 -module(opentelemetry).
 
 -export([set_default_tracer/1,
+         set_default_context_manager/1,
+         get_context_manager/0,
          get_tracer/0,
          get_tracer/1,
+         set_http_extractor/1,
+         get_http_extractor/0,
+         set_http_injector/1,
+         get_http_injector/0,
          timestamp/0,
          links/1,
          link/4,
@@ -43,6 +49,7 @@
          generate_span_id/0]).
 
 -include("opentelemetry.hrl").
+-include_lib("kernel/include/logger.hrl").
 
 -export_type([tracer/0,
               trace_id/0,
@@ -103,15 +110,50 @@
 
 -type http_headers()       :: [{unicode:unicode_binary(), unicode:unicode_binary()}].
 
+-spec set_default_tracer(tracer()) -> boolean().
 set_default_tracer(Tracer) ->
-    persistent_term:put({?MODULE, default_tracer}, Tracer).
+    verify_and_set_term(Tracer, default_tracer, ot_tracer).
 
+-spec set_default_context_manager(ot_ctx:context_manager()) -> boolean().
+set_default_context_manager(ContextManager) ->
+    verify_and_set_term(ContextManager, context_manager, ot_ctx).
+
+-spec get_context_manager() -> ot_ctx:context_manager().
+get_context_manager() ->
+    persistent_term:get({?MODULE, context_manager}, {ot_ctx_noop, []}).
+
+-spec get_tracer() -> tracer().
 get_tracer() ->
     persistent_term:get({?MODULE, default_tracer}, {ot_tracer_noop, []}).
 
+-spec get_tracer(unicode:unicode_binary()) -> tracer().
 get_tracer(_Name) ->
     persistent_term:get({?MODULE, default_tracer}, {ot_tracer_noop, []}).
 
+set_http_extractor(List) ->
+    Fun = fun(Headers) ->
+              lists:foldl(fun(Extract, ok) ->
+                              Extract(Headers),
+                              ok
+                          end, ok, List),
+              ok
+          end,
+    persistent_term:put({?MODULE, http_extractor}, Fun).
+
+set_http_injector(List) ->
+    Fun = fun(Headers) ->
+              lists:foldl(fun(Inject, HeadersAcc) ->
+                              Inject(HeadersAcc)
+                          end, Headers, List)
+          end,
+    persistent_term:put({?MODULE, http_injector}, Fun).
+
+get_http_extractor() ->
+    persistent_term:get({?MODULE, http_extractor}, fun(Headers) -> Headers end).
+
+get_http_injector() ->
+    persistent_term:get({?MODULE, http_injector}, fun(_Headers) -> ok end).
+
 -spec timestamp() -> integer().
 timestamp() ->
     erlang:system_time(nanosecond).
@@ -212,3 +254,36 @@ generate_span_id() ->
 
 uniform(X) ->
     rand:uniform(X).
+
+%% internal functions
+
+-spec verify_and_set_term(module() | {module(), term()}, term(), atom()) -> boolean().
+verify_and_set_term(Module, TermKey, Behaviour) ->
+    case verify_behaviour(Module, Behaviour) of
+        true ->
+            persistent_term:put({?MODULE, TermKey}, Module),
+            true;
+        false ->
+            ?LOG_WARNING("Module ~p does not implement behaviour ~p. "
+                         "A noop ~p will be used until a module, implementing "
+                         "the behaviour is configured.",
+                         [Module, Behaviour, Behaviour]),
+            false
+    end.
+
+-spec verify_behaviour(module() | {module(), term()}, atom()) -> boolean().
+verify_behaviour({Module, _}, Behaviour) ->
+    verify_behaviour(Module, Behaviour);
+verify_behaviour(Module, Behaviour) ->
+    try Module:module_info(attributes) of
+        Attributes ->
+            case lists:keyfind(behaviour, 1, Attributes) of
+                {behaviour, Behaviours} ->
+                    lists:member(Behaviour, Behaviours);
+                _ ->
+                    false
+            end
+    catch
+        error:undef ->
+            false
+    end.

src/ot_baggage.erl

@@ -0,0 +1,82 @@
+%%%------------------------------------------------------------------------
+%% Copyright 2019, OpenTelemetry Authors
+%% Licensed under the Apache License, Version 2.0 (the "License");
+%% you may not use this file except in compliance with the License.
+%% You may obtain a copy of the License at
+%%
+%% http://www.apache.org/licenses/LICENSE-2.0
+%%
+%% Unless required by applicable law or agreed to in writing, software
+%% distributed under the License is distributed on an "AS IS" BASIS,
+%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+%% See the License for the specific language governing permissions and
+%% limitations under the License.
+%%
+%% @doc
+%% @end
+%%%-------------------------------------------------------------------------
+-module(ot_baggage).
+
+-export([ctx_key/0,
+         set/2,
+         get/1,
+         remove/1,
+         clear/0,
+         get_http_propagators/0]).
+
+-type key() :: string().
+-type value() :: string().
+
+-export_type([key/0,
+              value/0]).
+
+-define(BAGGAGE_KEY, '$__ot_baggage_ctx_key').
+-define(BAGGAGE_HEADER, <<"Baggage-Context">>).
+ctx_key() ->
+    ?BAGGAGE_KEY.
+
+-spec set(key(), value()) -> ok.
+set(Key, Value) ->
+    ot_ctx:set_value(?BAGGAGE_KEY, Key, Value).
+
+-spec get(key()) -> value().
+get(Key)->
+    ot_ctx:get_value(?BAGGAGE_KEY, Key).
+
+-spec remove(key()) -> ok.
+remove(Key) ->
+    ot_ctx:remove(?BAGGAGE_KEY, Key).
+
+-spec clear() -> ok.
+clear() ->
+    ot_ctx:clear(?BAGGAGE_KEY).
+
+-spec get_http_propagators() -> {ot_propagation:http_extractor(), ot_propagation:http_injector()}.
+get_http_propagators() ->
+    ToText = fun(_Headers, undefined) ->
+                     [];
+                (_Headers, Baggage) ->
+                     case maps:fold(fun(Key, Value, Acc) ->
+                                              [$,, [Key, "=", Value] | Acc]
+                                      end, [], Baggage) of
+                         [$, | List] ->
+                             [{?BAGGAGE_HEADER, List}];
+                         _ ->
+                             []
+                     end
+             end,
+    FromText = fun(Headers, CurrentBaggage) ->
+                       case lists:keyfind(?BAGGAGE_HEADER, 1, Headers) of
+                           {_, String} ->
+                               Pairs = string:lexemes(String, [","]),
+                               lists:foldl(fun(Pair, Acc) ->
+                                                   [Key, Value] = string:split(Pair, "="),
+                                                   Acc#{Key => {Value, unlimited_propagation}}
+                                           end, CurrentBaggage, Pairs);
+                           _ ->
+                               CurrentBaggage
+                       end
+               end,
+    Inject = ot_ctx:http_injector(?BAGGAGE_KEY, ToText),
+    Extract = ot_ctx:http_extractor(?BAGGAGE_KEY, FromText),
+    {Extract, Inject}.

src/ot_correlations.erl

@@ -0,0 +1,69 @@
+%%%------------------------------------------------------------------------
+%% Copyright 2019, OpenTelemetry Authors
+%% Licensed under the Apache License, Version 2.0 (the "License");
+%% you may not use this file except in compliance with the License.
+%% You may obtain a copy of the License at
+%%
+%% http://www.apache.org/licenses/LICENSE-2.0
+%%
+%% Unless required by applicable law or agreed to in writing, software
+%% distributed under the License is distributed on an "AS IS" BASIS,
+%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+%% See the License for the specific language governing permissions and
+%% limitations under the License.
+%%
+%% @doc
+%% @end
+%%%-------------------------------------------------------------------------
+-module(ot_correlations).
+
+-export([ctx_key/0,
+         set/3,
+         get_http_propagators/0]).
+
+-type key() :: string().
+-type value() :: string().
+-type hop_limit() :: no_propagation | unlimited_propagation.
+
+-export_type([key/0,
+              value/0]).
+
+-define(CORRELATIONS_KEY, '$__ot_correlations_ctx_key').
+-define(CORRELATIONS_HEADER, <<"Correlation-Context">>).
+
+ctx_key() ->
+    ?CORRELATIONS_KEY.
+
+-spec set(key(), value(), hop_limit()) -> ok.
+set(Key, Value, HopLimit) ->
+    ot_ctx:set_value(?CORRELATIONS_KEY, Key, {Value, HopLimit}).
+
+-spec get_http_propagators() -> {ot_propagation:http_extractor(), ot_propagation:http_injector()}.
+get_http_propagators() ->
+    ToText = fun(_Headers, Correlations) ->
+                     case maps:fold(fun(Key, {Value, unlimited_propagation}, Acc) ->
+                                              [$,, [Key, "=", Value] | Acc];
+                                         (_Key, {_Value, no_propagation}, Acc) ->
+                                              Acc
+                               end, [], Correlations) of
+                         [$, | List] ->
+                             [{?CORRELATIONS_HEADER, List}];
+                         _ ->
+                             []
+                     end
+             end,
+    FromText = fun(Headers, CurrentCorrelations) ->
+                       case lists:keyfind(?CORRELATIONS_HEADER, 1, Headers) of
+                           {_, String} ->
+                               Pairs = string:lexemes(String, [","]),
+                               lists:foldl(fun(Pair, Acc) ->
+                                                   [Key, Value] = string:split(Pair, "="),
+                                                   Acc#{Key => {Value, unlimited_propagation}}
+                                           end, CurrentCorrelations, Pairs);
+                           _ ->
+                               CurrentCorrelations
+                       end
+               end,
+    Inject = ot_ctx:http_injector(?CORRELATIONS_KEY, ToText),
+    Extract = ot_ctx:http_extractor(?CORRELATIONS_KEY, FromText),
+    {Extract, Inject}.