shackle

High-Performance Erlang Network Client Framework

Requirements

• Erlang 19.0+

Features

• Backpressure via backlog (OOM protection)
• Fast pool implementation (random, round_robin)
• Managed timeouts
• Multi-protocol support (SSL / TCP / UDP)
• Performance-optimized
• Request pipelining
• Smart reconnect mechanism (exponential backoff)

Framework goals

• Reusability
• Speed
• Concurrency
• Safety

How-to

Implementing a client

-behavior(shackle_client).
-export([
    init/0,
    setup/2,
    handle_request/2,
    handle_data/2,
    terminate/1
]).

-record(state, {
    buffer =       <<>> :: binary(),
    request_counter = 0 :: non_neg_integer()
}).

-spec init(Options :: term()) ->
    {ok, State :: term()} |
    {error, Reason :: term()}.

init(_Options) ->
    {ok, #state {}}.

-spec setup(Socket :: inet:socket(), State :: term()) ->
    {ok, State :: term()} |
    {error, Reason :: term(), State :: term()}.

setup(Socket, State) ->
    case gen_tcp:send(Socket, <<"INIT">>) of
        ok ->
            case gen_tcp:recv(Socket, 0) of
                {ok, <<"OK">>} ->
                    {ok, State};
                {error, Reason} ->
                    {error, Reason, State}
            end;
        {error, Reason} ->
            {error, Reason, State}
    end.

-spec handle_request(Request :: term(), State :: term()) ->
    {ok, RequestId :: external_request_id(), Data :: iodata(), State :: term()}.

handle_request(noop,  State) ->
    Data = arithmetic_protocol:request(0, noop, 0, 0),

    {ok, undefined, Data, State};
handle_request({Operation, A, B}, #state {
        request_counter = RequestCounter
    } = State) ->

    RequestId = request_id(RequestCounter),
    Data = request(RequestId, Operation, A, B),

    {ok, RequestId, Data, State#state {
        request_counter = RequestCounter + 1
    }}.

-spec handle_data(Data :: binary(), State :: term()) ->
    {ok, [{RequestId :: external_request_id(), Reply :: term()}], State :: term()}.

handle_data(Data, #state {
        buffer = Buffer
    } = State) ->

    Data2 = <<Buffer/binary, Data/binary>>,
    {Replies, Buffer2} = parse_replies(Data2, []),

    {ok, Replies, State#state {
        buffer = Buffer2
    }}.

-spec terminate(State :: term()) -> ok.

terminate(_State) -> ok.

Starting client pool

shackle_pool:start(pool_name(), client(), client_options(), pool_options())

client_options:

Name	Type	Default	Description
address	inet:ip_address() | inet:hostname()	"127.0.0.1"	server address (formerly ip)
port	inet:port_number()	undefined	server port
protocol	shackle_tcp | shackle_udp | shackle_ssl	shackle_tcp	server protocol
reconnect	boolean()	true	reconnect closed connections
reconnect_time_max	pos_integer() | infinity	120000	maximum reconnect time in milliseconds
reconnect_time_min	pos_integer()	1000	minimum reconnect time in milliseconds
socket_options	[gen_tcp:connect_option() | gen_udp:option()]	[]	options passed to the socket

pool_options:

Name	Type	Default	Description
backlog_size	pos_integer() | infinity	1024	maximum number of concurrent requests per connection
max_retries	non_neg_integer()	3	maximum number of tries to find an active server
pool_size	pos_integer()	16	number of connections
pool_strategy	random | round_robin	random	connection selection strategy

Calling / Casting client

1> shackle:call(pool_name, {get, <<"test">>}).
{ok, <<"bar">>}

2> {ok, ReqId} = shackle:cast(pool_name, {get, <<"foo">>}, 500).
{ok, {anchor, anchor_client, #Ref<0.0.0.2407>}}

3> shackle:receive_response(ReqId).
{ok, <<"bar">>}

Environment variables

Name	Type	Default	Description
hooks	[{atom(), {module(), atom()}}]	[]	used to receive events/metrics about your client

Hooks

Hooks allow you to receive events and metrics about your client. To do so you need to implement the shackle_hooks behaviour and then use the hooks environment variable.

-module(my_client_hooks).

-behaviour(shackle_hooks).
-export([
    metrics/4
]).

metrics(Client, counter, Key, Value) ->
    statsderl:increment(key(Client, Key), Value, 0.005);
metrics(Client, timing, Key, Value) ->
    statsderl:timing(key(Client, Key), Value, 0.005).

key(Client, Key) ->
    [<<"shackle.">>, atom_to_binary(Client, latin1), <<".">>, Key].

{shackle, [
  {hooks, [
    {metrics {my_client_hooks, metrics}}
  ]}
]}

Tests

make dialyzer
make eunit
make xref

Performance testing

To run performance testing targets you must first start the server:

./bin/server.sh

Then you can run the bench or profile target:

make bench
make profile

Clients

Name	Description
anchor	Memcached Client
buoy	HTTP 1.1 Client
flare	Kafka Producer
marina	Cassandra CQL Client
statsderl	StatsD Client

License

The MIT License (MIT)

Copyright (c) 2015-2020 Louis-Philippe Gauthier

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.