opentelemetry

%%%------------------------------------------------------------------------
%% Copyright 2021, 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 Merges environment variable configuration values with application
%% configuration. The OS environment variables take precedence over the
%% application environment.
%% @end
%%%-------------------------------------------------------------------------
-module(otel_configuration).

-export([merge_with_os/1,
         merge_list_with_environment/3,
         report_cb/1]).

-include_lib("kernel/include/logger.hrl").

-define(BATCH_PROCESSOR_DEFAULTS, #{scheduled_delay_ms => 5000,
                                    exporting_timeout_ms => 30000,
                                    max_queue_size => 2048,
                                    exporter => {opentelemetry_exporter, #{}}}).
-define(SIMPLE_PROCESSOR_DEFAULTS, #{exporting_timeout_ms => 30000,
                                     exporter => {opentelemetry_exporter, #{}}}).

%% required configuration
%% using a map instead of a record because there can be more values
-type t() :: #{log_level := atom(),
               register_loaded_applications := boolean() | undefined,
               create_application_tracers := boolean() | undefined,
               id_generator := module(),
               deny_list := [atom()],

               resource_detectors := [module()],
               resource_detector_timeout := integer(),
               bsp_scheduled_delay_ms := integer() | undefined,
               bsp_exporting_timeout_ms := integer() | undefined,
               bsp_max_queue_size := integer() | undefined,
               ssp_exporting_timeout_ms := integer() | undefined,
               text_map_propagators := [atom()],
               traces_exporter := {atom(), term()} | undefined,
               metrics_exporter := {atom(), term()} | undefined,
               processors := list(),
               sampler := {atom(), term()},
               sweeper := #{interval => integer() | infinity,
                            strategy => atom() | fun(),
                            span_ttl => integer() | infinity,
                            storage_size => integer() | infinity},
               attribute_count_limit := integer(),
               attribute_value_length_limit := integer() | infinity,
               event_count_limit := integer(),
               link_count_limit := integer(),
               attribute_per_event_limit := integer(),
               attribute_per_link_limit := integer()}.

-spec new() -> t().
new() ->
    #{log_level => info,
      register_loaded_applications => undefined,
      create_application_tracers => undefined,
      id_generator => otel_id_generator,
      deny_list => [],
      resource_detectors => [otel_resource_env_var,
                             otel_resource_app_env],
      resource_detector_timeout => 5000,
      bsp_scheduled_delay_ms => undefined,
      bsp_exporting_timeout_ms => undefined,
      bsp_max_queue_size => undefined,
      ssp_exporting_timeout_ms => undefined,
      text_map_propagators => [trace_context, baggage],
      traces_exporter => {opentelemetry_exporter, #{}},
      metrics_exporter => {opentelemetry_exporter, #{}},
      processors => [{otel_batch_processor, ?BATCH_PROCESSOR_DEFAULTS}],
      sampler => {parent_based, #{root => always_on}},
      sweeper => #{interval => timer:minutes(10),
                   strategy => drop,
                   span_ttl => timer:minutes(30),
                   storage_size => infinity},
      attribute_count_limit => 128,
      attribute_value_length_limit => infinity,
      event_count_limit => 128,
      link_count_limit => 128,
      attribute_per_event_limit => 128,
      attribute_per_link_limit => 128}.

-spec merge_with_os(list()) -> t().
merge_with_os(AppEnv) ->
    ConfigMap = new(),

    lists:foldl(fun(F, Acc) ->
                        F(AppEnv, Acc)
                end, ConfigMap, [fun span_limits/2,
                                 fun general/2,
                                 fun sampler/2,
                                 fun processors/2,
                                 fun sweeper/2]).

-spec span_limits(list(), t()) -> t().
span_limits(AppEnv, ConfigMap) ->
    merge_list_with_environment(config_mappings(span_limits), AppEnv, ConfigMap).

-spec general(list(), t()) -> t().
general(AppEnv, ConfigMap) ->
    Config = merge_list_with_environment(config_mappings(general_sdk), AppEnv, ConfigMap),

    %% merge the old `register_loaded_applications' with the new config key
    %% `create_application_tracers' that has replaced it
    Config1 = maps:update_with(create_application_tracers,
                               fun(undefined) ->
                                       %% `create_application_tracers' isn't set so update
                                       %% with the `register_loaded_applications' value
                                       %% or `true' if it too isn't set
                                       case maps:get(register_loaded_applications, Config) of
                                           undefined ->
                                               true;
                                           Bool ->
                                               Bool
                                       end;
                                  (Bool) ->
                                       Bool
                               end, Config),

    Config1.

-spec sweeper(list(), t()) -> t().
sweeper(AppEnv, ConfigMap=#{sweeper := DefaultSweeperConfig}) ->
    AppEnvSweeper = proplists:get_value(sweeper, AppEnv, #{}),

    %% convert sweeper config to a list to utilize the merge_list_with_environment function
    SweeperConfig = merge_list_with_environment(config_mappings(sweeper),
                                                maps:to_list(AppEnvSweeper),
                                                DefaultSweeperConfig),
    ConfigMap#{sweeper => SweeperConfig}.

-spec processors(list(), t()) -> t().
processors(AppEnv, ConfigMap) ->
    SpanProcessors = case transform(span_processor, proplists:get_value(span_processor, AppEnv)) of
                         undefined ->
                             Processors = proplists:get_value(processors, AppEnv, maps:get(processors, ConfigMap)),
                             transform(span_processors, Processors);
                         SpanProcessor ->
                             case proplists:get_value(processors, AppEnv) of
                                 undefined ->
                                     ok;
                                 _ ->
                                     ?LOG_INFO("both processors and span_processor set in configuration but "
                                               "only one should be used. span_processor will be ignored.")
                             end,

                             [SpanProcessor]
                     end,

    ProcessorsConfig = lists:map(fun({Name, Opts}) ->
                                         Opts1 = merge_processor_config(Name, Opts, AppEnv),
                                         {Name, Opts1}
                                 end, SpanProcessors),

    ConfigMap#{processors := ProcessorsConfig}.

%% use the top level app env and os env configuration to set processor config values
merge_processor_config(otel_batch_processor, Opts, AppEnv) ->
    BatchEnvMapping = [{bsp_scheduled_delay_ms, scheduled_delay_ms},
                       {bsp_exporting_timeout_ms, exporting_timeout_ms},
                       {bsp_max_queue_size, max_queue_size},
                       {traces_exporter, exporter}],

    lists:foldl(fun({K, V}, Acc) ->
                     case proplists:get_value(K, AppEnv) of
                         undefined ->
                             Acc;
                         Value ->
                             Acc#{V => Value}
                     end
                end, Opts, BatchEnvMapping);
merge_processor_config(otel_simple_processor, Opts, AppEnv) ->
    SimpleEnvMapping = [{ssp_exporting_timeout_ms, exporting_timeout_ms}],

    lists:foldl(fun({K, V}, Acc) ->
                     case proplists:get_value(K, AppEnv) of
                         undefined ->
                             Acc;
                         Value ->
                             Acc#{V => Value}
                     end
                end, Opts, SimpleEnvMapping);
merge_processor_config(_, Opts, _) ->
    Opts.


%% sampler configuration is unique since it has the _ARG that is a sort of
%% sub-configuration of the sampler config, and isn't a list.
-spec sampler(list(), t()) -> t().
sampler(AppEnv, ConfigMap) ->
    OSVar = "OTEL_TRACES_SAMPLER",
    Key = sampler,
    Transform = sampler,
    case os:getenv("OTEL_TRACES_SAMPLER") of
        false ->
            case proplists:get_value(Key, AppEnv) of
                undefined ->
                    ConfigMap;
                Sampler ->
                    update_config_map(OSVar, Key, Transform, Sampler, ConfigMap)
            end;
        OSEnvSampler->
            SamplerTuple = {OSEnvSampler, os:getenv("OTEL_TRACES_SAMPLER_ARG")},
            update_config_map(OSVar, Key, Transform, SamplerTuple, ConfigMap)
    end.

%% requires `ConfigMap' contains every key and its default
%% will replace the defaults with the value from either the OS environment or application
%% environment, with the OS environment taking precedence.
-spec merge_list_with_environment([{OSVar, Key, Transform}], AppEnv, ConfigMap) -> ConfigMap
              when OSVar :: string(),
                   Key :: atom(),
                   Transform :: atom(),
                   AppEnv :: [{atom(), term()}],
                   ConfigMap :: map().
merge_list_with_environment(ConfigMappings, AppEnv, ConfigMap) ->
    lists:foldl(fun({OSVar, Key, Transform}, Acc) ->
                        case os:getenv(OSVar) of
                            false ->
                                %% not in the OS environment so check application environment
                                case lists:keyfind(Key, 1, AppEnv) of
                                    false ->
                                        %% not in the application env so leave default
                                        Acc;
                                    {_, Value} ->
                                        %% transform even the value from the
                                        %% application environment to ensure it
                                        %% is of the right type/format
                                        update_config_map(OSVar, Key, Transform, Value, Acc)
                                end;
                            OSVal ->
                                update_config_map(OSVar, Key, Transform, OSVal, Acc)
                        end
                end, ConfigMap, ConfigMappings).

update_config_map(OSVar, Key, Transform, Value, ConfigMap) ->
    try transform(Transform, Value) of
        TransformedValue ->
            ConfigMap#{Key := TransformedValue}
    catch
        Kind:Reason:StackTrace ->
            ?LOG_INFO(#{source => transform,
                        kind => Kind,
                        reason => Reason,
                        os_var => OSVar,
                        key => Key,
                        transform => Transform,
                        value => Value,
                        stacktrace => StackTrace},
                      #{report_cb => fun ?MODULE:report_cb/1}),
            ConfigMap
    end.

report_cb(#{source := transform,
            kind := Kind,
            reason := Reason,
            os_var := OSVar,
            key := Key,
            transform := Transform,
            value := Value,
            stacktrace := StackTrace}) ->
    {"Transforming configuration value failed: os_var=~ts key=~ts transform=~ts value=~ts exception=~ts",
     [OSVar, Key, Transform, Value, otel_utils:format_exception(Kind, Reason, StackTrace)]}.

config_mappings(general_sdk) ->
    [{"OTEL_LOG_LEVEL", log_level, existing_atom},

     %% `register_loaded_applications' is kept for backwards compatibility
     {"OTEL_REGISTER_LOADED_APPLICATIONS", register_loaded_applications, boolean},
     {"OTEL_CREATE_APPLICATION_TRACERS", create_application_tracers, boolean},

     {"OTEL_ID_GENERATOR", id_generator, existing_atom},
     {"OTEL_DENY_LIST", deny_list, existing_atom_list},
     {"OTEL_PROPAGATORS", text_map_propagators, propagators},
     {"OTEL_TRACES_EXPORTER", traces_exporter, exporter},
     {"OTEL_METRICS_EXPORTER", metrics_exporter, exporter},
     {"OTEL_RESOURCE_DETECTORS", resource_detectors, existing_atom_list},
     {"OTEL_RESOURCE_DETECTOR_TIMEOUT", resource_detector_timeout, integer},

     {"OTEL_BSP_SCHEDULE_DELAY_MILLIS", bsp_scheduled_delay_ms, integer},
     {"OTEL_BSP_EXPORT_TIMEOUT_MILLIS", bsp_exporting_timeout_ms, integer},
     {"OTEL_BSP_MAX_QUEUE_SIZE", bsp_max_queue_size, integer},
     %% the following is not supported yet
     %% {"OTEL_BSP_MAX_EXPORT_BATCH_SIZE", bsp_max_export_batch_size, integer}

     {"OTEL_SSP_EXPORT_TIMEOUT_MILLIS", ssp_exporting_timeout_ms, integer}
    ];
config_mappings(span_limits) ->
    [{"OTEL_SPAN_ATTRIBUTE_COUNT_LIMIT", attribute_count_limit, integer},
     {"OTEL_SPAN_ATTRIBUTE_VALUE_LENGTH_LIMIT", attribute_value_length_limit, integer_infinity},
     {"OTEL_SPAN_EVENT_COUNT_LIMIT", event_count_limit, integer},
     {"OTEL_SPAN_LINK_COUNT_LIMIT", link_count_limit, integer},
     {"OTEL_EVENT_ATTRIBUTE_COUNT_LIMIT", attribute_per_event_limit, integer},
     {"OTEL_LINK_ATTRIBUTE_COUNT_LIMIT", attribute_per_link_limit, integer}%% ,
     %% {"OTEL_ATTRIBUTE_VALUE_LENGTH_LIMIT", attribute_value_length_limit, integer},
     %% {"OTEL_ATTRIBUTE_COUNT_LIMIT", attribute_per_link_limit, integer}
    ];
config_mappings(sweeper) ->
    [{"OTEL_SPAN_SWEEPER_INTERVAL", interval, integer_infinity},
     {"OTEL_SPAN_SWEEPER_STRATEGY", strategy, atom_or_fun},
     {"OTEL_SPAN_SWEEPER_SPAN_TTL", span_ttl, integer_infinity},
     {"OTEL_SPAN_SWEEPER_STORAGE_SIZE", storage_size, integer_infinity}
    ].

transform(_, undefined) ->
    undefined;
transform(existing_atom_list, [A | _]=List) when is_atom(A) ->
    List;
transform(existing_atom_list, String) when is_list(String) ->
    List = string:split(String, ",", all),
    lists:filtermap(fun(A) ->
                            try transform(existing_atom, string:trim(A)) of
                                Value ->
                                    {true, Value}
                            catch
                                _:_ ->
                                    false
                            end
                    end, List);
transform(exporter, Exporter) when Exporter =:= "otlp" ; Exporter =:= otlp ->
    {opentelemetry_exporter, #{}};
transform(exporter, Exporter) when Exporter =:= "jaeger" ; Exporter =:= jaeger ->
    ?LOG_WARNING("configuring jaeger exporter through OTEL_TRACES_EXPORTER is not yet supported ", []),
    undefined;
transform(exporter, Exporter)  when Exporter =:= "zipkin" ; Exporter =:= zipkin ->
    ?LOG_WARNING("configuring zipkin exporter through OTEL_TRACES_EXPORTER is not yet supported ", []),
    undefined;
transform(exporter, Exporter) when Exporter =:= "none" ; Exporter =:= none ->
    undefined;
transform(exporter, Value={Term, _}) when is_atom(Term) ->
    Value;
transform(exporter, UnknownExporter) when is_list(UnknownExporter) ->
    ?LOG_WARNING("unknown exporter ~p. falling back to default otlp", [UnknownExporter]),
    {opentelemetry_exporter, #{}};

transform(integer_infinity, infinity) ->
    infinity;
transform(integer_infinity, Value) ->
    transform(integer, Value);
transform(integer, Value) when is_integer(Value) ->
    Value;
transform(integer, Value) when is_list(Value) ->
    list_to_integer(Value);
transform(existing_atom, Value) when is_atom(Value) ->
    Value;
transform(existing_atom, Value) when is_list(Value) ->
    list_to_existing_atom(Value);
transform(atom_or_fun, Value) when is_list(Value) ->
    list_to_existing_atom(Value);
transform(atom_or_fun, Value) when is_atom(Value) ->
    Value;
transform(atom_or_fun, Value) when is_function(Value) ->
    Value;
transform(boolean, Value) when is_boolean(Value) ->
    Value;
transform(boolean, "true") ->
    true;
transform(boolean, "false") ->
    false;
transform(url, Value=#{}) ->
    Value;
transform(url, Value) ->
    uri_string:parse(Value);
%% convert sampler string to usable configuration term
transform(sampler, {"parentbased_always_on", _}) ->
    {parent_based, #{root => always_on}};
transform(sampler, {"parentbased_always_off", _}) ->
    {parent_based, #{root => always_off}};
transform(sampler, {"always_on", _}) ->
    always_on;
transform(sampler, {"always_off", _}) ->
    always_off;
transform(sampler, {"traceidratio", false}) ->
    {trace_id_ratio_based, 1.0};
transform(sampler, {"traceidratio", Probability}) ->
    {trace_id_ratio_based, probability_string_to_float(Probability)};
transform(sampler, {"parentbased_traceidratio", false}) ->
    {parent_based, #{root => {trace_id_ratio_based, 1.0}}};
transform(sampler, {"parentbased_traceidratio", Probability}) ->
    {parent_based, #{root => {trace_id_ratio_based, probability_string_to_float(Probability)}}};
transform(sampler, Value) ->
    Value;
transform(key_value_list, Value) when is_list(Value) ->
    case io_lib:printable_unicode_list(Value) of
        true ->
            Pairs = string:split(Value, ",", all),
            lists:filtermap(fun(Pair) ->
                                    case string:split(Pair, "=", all) of
                                        [K, V] ->
                                            V1 = re:replace(string:trim(V), "^\"|\"$", "", [global, {return, list}]),
                                            {true, {string:trim(K), V1}};
                                        _ ->
                                            false
                                    end
                            end, Pairs);
        false ->
            Value
    end;
transform(propagators, [P | _]=Propagators) when is_atom(P) ->
    lists:filtermap(fun(Propagator) ->
                            case transform(propagator, Propagator) of
                                undefined ->
                                    false;
                                Value ->
                                    {true, Value}
                            end
                    end, Propagators);
transform(propagators, PropagatorsString) when is_list(PropagatorsString) ->
    Propagators = string:split(PropagatorsString, ",", all),
    lists:filtermap(fun(Propagator) when is_list(Propagator) ->
                          case transform(propagator, string:trim(Propagator)) of
                              undefined ->
                                  false;
                              Value ->
                                  {true, Value}
                          end
                  end, Propagators);

transform(propagator, Value) when Value =:= "tracecontext" ;
                                  Value =:= tracecontext ;
                                  Value =:= trace_context ->
    trace_context;
transform(propagator, Value) when Value =:= "baggage" ;
                                  Value =:= baggage ->
    baggage;
transform(propagator, Value) when Value =:= "b3multi" ;
                                  Value =:= b3multi ->
    b3multi;
transform(propagator, Value) when Value =:= "b3" ;
                                  Value =:= b3 ->
    b3;
%% TODO: support jager propagator format
%% transform(propagator, "jaeger") ->
%%     jaeger;
transform(propagator, Propagator) ->
    ?LOG_WARNING("Ignoring unknown propagator ~ts in OS environment variable $OTEL_PROPAGATORS",
                 [Propagator]),
    undefined;
transform(span_processors, Processors) when is_list(Processors) ->
    [transform(span_processor, Processor) || Processor <- Processors];
transform(span_processors, Unknown) ->
    ?LOG_WARNING("processors value must be a list, but ~ts given. No span processors will be used", [Unknown]),
    [];
transform(span_processor, batch) ->
    {otel_batch_processor, ?BATCH_PROCESSOR_DEFAULTS};
transform(span_processor, simple) ->
    {otel_simple_processor, ?SIMPLE_PROCESSOR_DEFAULTS};
transform(span_processor, SpanProcessor) ->
    SpanProcessor.

probability_string_to_float(Probability) ->
    try list_to_float(Probability) of
        Float ->
            Float
    catch
        error:badarg when Probability =:= "1" ->
            1.0;
         error:badarg when Probability =:= "0" ->
            0.0;
        error:badarg ->
            ?LOG_WARNING("Unable to convert $OTEL_TRACE_SAMPLER_ARG string value ~ts to float, using 1.0"),
            1.0
    end.