swirl

High Performance Erlang Stream Processor

Requirements

• Erlang 22.0 +

Environment variables

Name	Type	Default	Description
mappers_max	pos_integer()	100	maximum number of mappers
reducers_max	pos_integer()	100	maximum number of reducers

Examples

Starting a flow

ok = application:start(swirl),

FlowMod = swirl_flow_example,
FlowOpts = [
    {stream_names, [delivery]},
    {stream_filter, "exchange_id = 3 AND bidder_id IS NOT NULL"}
],
MapperNodes = [node()],
ReducerNode = node(),
{ok, Flow} = swirl_flow:start(FlowMod, FlowOpts, MapperNodes, ReducerNode),

StreamName = delivery,
Event = #{exchange_id => 1, bidder_id => 10},

swirl_stream:emit(StreamName, Event),

ok = swirl_flow:stop(Flow)

Implementing a flow

-module(swirl_flow_example).
-include_lib("swirl/include/swirl.hrl").

-behavior(swirl_flow).
-export([
    map/3,
    reduce/3,
    output/4
]).

%% swirl_flow callbacks
map(StreamName, Event, _MapperOpts) ->
    Type = ?L(type, Event),
    ExchangeId = ?L(exchange_id, Event),
    BidderId = ?L(bidder_id, Event),

    Key = {Type, StreamName, ExchangeId, BidderId},
    CounterIncrements = {1, 10},

    {Key, CounterIncrements}.

reduce(_Flow, Row, _ReducerOpts) ->
    Row.

output(_Flow, _Period, Rows, OutputOpts) ->
    %% do something with the output
    io:format("rows: ~p~n", [Rows]),

Stream Filter

exchange_id = 3 AND bidder_id IS NOT NULL
flight_id in (10, 12, 23) OR tag_id = 20
buyer_id notnull AND seller_id > 103

Swirl QL

variables:

atom()

values:

integer() | float() | binary()

boolean operators:

'and' | 'or'

comparison operators:

'<' | '<=' | '=' | '>=' | '>' | '<>'

inclusion operators:

in | notin

null operators:

null | notnull

TODO

• node discovery
• boolean expression indexing

Tests

make dialyzer
make elvis
make eunit
make xref

License

The MIT License (MIT)

Copyright (c) 2013-2024 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
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