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Apache Kafka Erlang client library
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src/brod_group_subscriber_worker.erl
%%%
%%% Copyright (c) 2019-2021 Klarna Bank AB (publ)
%%%
%%% 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.
%%%
%%% @private
-module(brod_group_subscriber_worker).
-behaviour(brod_topic_subscriber).
-include("brod_int.hrl").
%% brod_topic_subscriber callbacks
-export([init/2, handle_message/3, handle_info/2, terminate/2]).
-type start_options() ::
#{ group_id := brod:group_id()
, topic := brod:topic()
, partition := brod:partition()
, begin_offset := brod:offset() | ?undef
, cb_module := module()
, cb_config := term()
, commit_fun := brod_group_subscriber_v2:commit_fun()
}.
-record(state,
{ start_options :: start_options()
, cb_module :: module()
, cb_state :: term()
, commit_fun :: brod_group_subscriber_v2:commit_fun()
}).
-export_type([start_options/0]).
%%%===================================================================
%%% brod_topic_subscriber callbacks
%%%===================================================================
init(Topic, StartOpts) ->
#{ cb_module := CbModule
, cb_config := CbConfig
, partition := Partition
, begin_offset := BeginOffset
, commit_fun := CommitFun
} = StartOpts,
InitInfo = maps:with( [topic, partition, group_id, commit_fun]
, StartOpts
),
?BROD_LOG_INFO("Starting group_subscriber_worker: ~p~n"
"Offset: ~p~nPid: ~p~n"
, [InitInfo, BeginOffset, self()]
),
{ok, CbState} = CbModule:init(InitInfo, CbConfig),
State = #state{ start_options = StartOpts
, cb_module = CbModule
, cb_state = CbState
, commit_fun = CommitFun
},
CommittedOffsets = resolve_committed_offsets(Topic, Partition, BeginOffset),
{ok, CommittedOffsets, State}.
handle_message(_Partition, Msg, State) ->
#state{ cb_module = CbModule
, cb_state = CbState
, commit_fun = Commit
} = State,
case CbModule:handle_message(Msg, CbState) of
{ok, commit, NewCbState} ->
NewState = State#state{cb_state = NewCbState},
Commit(get_last_offset(Msg)),
{ok, ack, NewState};
{ok, ack, NewCbState} ->
%% Unlike the old group_subscriber here `ack' means just `ack'
%% without commit
NewState = State#state{cb_state = NewCbState},
{ok, ack, NewState};
{ok, NewCbState} ->
NewState = State#state{cb_state = NewCbState},
{ok, NewState}
end.
handle_info(Info, #state{cb_module = CbModule , cb_state = CbState} = State) ->
%% Any unhandled messages are forwarded to the callback module to
%% support arbitrary message-passing.
%% Only the {noreply, State} return value is supported.
case brod_utils:optional_callback(CbModule, handle_info, [Info, CbState], {noreply, CbState}) of
{noreply, NewCbState} ->
{noreply, State#state{cb_state = NewCbState}}
end.
terminate(Reason, #state{cb_module = CbModule, cb_state = State}) ->
brod_utils:optional_callback(CbModule, terminate, [Reason, State], ok).
%%%===================================================================
%%% Internal functions
%%%===================================================================
-spec get_last_offset(brod:message() | brod:message_set()) ->
brod:offset().
get_last_offset(#kafka_message{offset = Offset}) ->
Offset;
get_last_offset(#kafka_message_set{messages = Messages}) ->
#kafka_message{offset = Offset} = lists:last(Messages),
Offset.
resolve_committed_offsets(_T, _P, ?undef) ->
%% the default begin offset in consumer config will be used
[];
resolve_committed_offsets(_T, Partition, Offset) when ?IS_SPECIAL_OFFSET(Offset) ->
[{Partition, Offset}];
resolve_committed_offsets(_T, Partition, Offset) when is_integer(Offset) andalso Offset >= 0 ->
%% Note: brod_topic_subscriber expects
%% _acked_ offset rather than _begin_ offset
%% in `init' callback return. In order to get
%% begin offset it increments the value,
%% which we don't want, hence decrement.
[{Partition, Offset - 1}];
resolve_committed_offsets(Topic, Partition, Offset) ->
?BROD_LOG_WARNING("Discarded invalid committed offset ~p for: ~s:~p~n",
[Topic, Partition, Offset]),
[].