Kafka client library in Erlang

Supports v0.8+.
Why "brod"? http://en.wikipedia.org/wiki/Max_Brod

Building and testing

make
make clean test

Usage

Producer as a part of an application

In gen_server's init/1:

% Producer will be linked to the calling process
{ok, Producer} = brod:start_link_producer(Hosts, RequiredAcks, AckTimeout, ClientId),
{ok, #state{ producer = Producer }}.

Sending a message:

{ok, Ref} = brod:produce( State#state.producer
                        , Topic
                        , Partition
                        , [{Key, Value}]),
% remember the Ref somewhere, e.g. in #state{}

Handling acks from kafka broker:

handle_info({{Ref, P}, ack}, #state{producer = P} = State) ->
  % do something with Ref, e.g. notify a client and remove from #state{}

Sending a message with a blocking call:

ok = brod:produce_sync( State#state.producer
                      , Topic
                      , Partition
                      , [{Key, Value}]).

Consumer as a part of an application

Include brod.hrl:

-include_lib("brod/include/brod.hrl").

In gen_server's init/1:

% Consumer will be linked to the calling process
{ok, Consumer} = brod:start_link_consumer(Hosts, Topic, Partition),
Self = self(),
Callback = fun(#message_set{} = MsgSet) -> gen_server:call(Self, MsgSet) end,
ok = brod:consume(Consumer, Callback, Offset),
{ok, #state{ consumer = Consumer }}.

Handler:

handle_call(#message_set{messages = Msgs}, _From, State) ->
  lists:foreach(
    fun(#message{offset = Offset, key = K, value = V}) ->
        io:format(user, "[~p] ~s:~s\n", [Offset, K, V]),
    end, Msgs),
  {reply, ok, State};

More simple consumer callback (no need to include brod.hrl)

In gen_server's init/1:

{ok, Consumer} = brod:start_link_consumer(Hosts, Topic, Partition),
Self = self(),
Callback = fun(Offset, Key, Value) -> gen_server:call(Self, {msg, Offset, Key, Value}) end,
ok = brod:consume(Consumer, Callback, Offset),
{ok, #state{ consumer = Consumer }}.

Handler:

handle_call({msg, Offset, Key, Value}, _From, State) ->
  io:format(user, "[~p] ~s:~s\n", [Offset, Key, Value]),
  {reply, ok, State};

In erlang shell

rr(brod).
Hosts = [{"localhost", 9092}].
Topic = <<"t">>.
Partition = 0.
{ok, Producer} = brod:start_link_producer(Hosts).
{ok, Consumer} = brod:start_link_consumer(Hosts, Topic, Partition).
Callback = fun(Offset, Key, Value) -> io:format(user, "[~p] ~s:~s\n", [Offset, Key, Value]) end.
ok = brod:consume(Consumer, Callback, -1).
brod:produce_sync(Producer, Topic, Partition, <<"k">>, <<"v">>).

Simple consumers

f(C), C = brod:console_consumer(Hosts, Topic, Partition, -1).
% this will print messages from the Topic on your stdout
C ! stop.
f(C), C = brod:file_consumer(Hosts, Topic, Partition, -1, "/tmp/kafka.log").
% this will write messages to /tmp/kafka.log
C ! stop.

Other API to play with/inspect kafka

These functions open a connetion to kafka cluster, send a request, await response and then close the connection.

Hosts = [{"localhost", 9092}].
Topic = <<"topic">>.
Partition = 0.
brod:get_metadata(Hosts).
brod:get_metadata(Hosts, [Topic]).
brod:get_offsets(Hosts, Topic, Partition).
brod:fetch(Hosts, Topic, Partition, 1).

Standalone binary

This will build a standalone binary with brod application

make escriptize
./brod help