High-performance Erlang client for the Redis key-value store.

hierdis presents a simple API similar to the synchronous API exposed by the well-known hiredis C client. This is done by exposing hiredis C client functionality to Erlang through the NIF interface.

Using this approach also allows hierdis to communicate with Redis via unix domain sockets, which by itself can provide a 50% increase in throughput over TCP.

This is the fork of basho-labs/hierdis. The latter seems abandoned and it lacks these important features:

• auto-reconnect
• timeouts
• tests

#####Get a Redis connection.

> {ok,C} = hierdis:connect_unix("/tmp/redis.sock").
{ok,<<>>}

> {ok,C3} = hierdis:connect("127.0.0.1", 6379).
{ok,<<>>}

#####Issue single commands to Redis as an iolist.

> hierdis:command(C, ["SET", "foo", "bar"]).
{ok,<<"OK">>}
> hierdis:command(C, ["GET", "foo"]).
{ok,<<"bar">>}
> hierdis:command(C, ["MSET" | ["key1", "1", "key2", "2", "key3", "3"]]).
{ok,<<"OK">>}
> hierdis:command(C, ["GET", "key1"]).
{ok,<<"1">>}
> hierdis:command(C, ["GET", "key3"]).
{ok,<<"3">>}
> hierdis:command(C, ["MGET" | ["key1", "key2", "key3"]]).
{ok,[<<"1">>,<<"2">>,<<"3">>]}
> hierdis:command(C, ["GET", "foo"], 5000).
{ok,<<"bar">>}

#####Pipeline commands to Redis as a list of iolists.

> hierdis:pipeline(C, [
    ["SET", "foo", "bar"],
    ["GET", "foo"],
    ["MSET" | ["key1", "1", "key2", "2", "key3", "3"]],
    ["GET", "key1"],
    ["GET", "key3"],
    ["MGET" | ["key1", "key2", "key3"]]
]).
[{ok,<<"OK">>},
 {ok,<<"bar">>},
 {ok,<<"OK">>},
 {ok,<<"1">>},
 {ok,<<"3">>},
 {ok,[<<"1">>,<<"2">>,<<"3">>]}]

#####Execute a transaction pipeline against Redis as a list of iolists.

> hierdis:transaction(C, [
    ["SET", "foo", "bar"],
    ["GET", "foo"],
    ["MSET" | ["key1", "1", "key2", "2", "key3", "3"]],
    ["MGET" | ["key1", "key2", "key3"]]
]).
{ok,[<<"OK">>,<<"bar">>,<<"OK">>,[<<"1">>,<<"2">>,<<"3">>]]}
> hierdis:transaction(C, [
    ["SET", "foo", "bar"],
    ["GET", "foo"],
    ["CRASHER!" | ["ka", "blooey"]],
    ["MGET" | ["key1", "key2", "key3"]]
]).
{error,{redis_reply_error,"EXECABORT Transaction discarded because of previous errors."}}

#####Manually append commands and get replies.

> hierdis:append_command(C, ["MULTI"]).
{ok,15}
> hierdis:append_command(C, ["SET", "foo", "pipelined"]).
{ok,52}
> hierdis:append_command(C, ["SET", "bar", "linedpipe"]).
{ok,89}
> hierdis:append_command(C, ["EXEC"]).
{ok,103}
> hierdis:get_reply(C).
{ok,<<"OK">>}
> hierdis:get_reply(C).
{ok,<<"QUEUED">>}
> hierdis:get_reply(C).
{ok,<<"QUEUED">>}
> hierdis:get_reply(C).
{ok,[<<"OK">>,<<"OK">>]}

#####Set read/write timeout once for the connection

If you don't want to set timeout for individual operations, you can set it once for all read/write operations for the lifetime of the connection.

> hierdis:set_timeout(C, 5000). % ms
ok

The general behavior is very similar to eredis reconnecting, except the fact that this client is not running in background, therefore won't be trying to reconnect every N seconds. Instead, it will try to reconnect before every operation (command, pipeline, etc.).

Note that if you don't set a timeout (using either connect/4 or connect_unix/3), reconnect will block for some time (until your Redis shows up again).

On a MacBook Air equipped with a dual-core 2.0Ghz Core i7 CPU hierdis achieves over 3x the throughput and sees 5x lower latency compared to eredis using 1 byte values. When increasing the size of the stored values to 10 kb the performance of hierdis remained basically constant, and eredis performance cut in half.

Tests were performed using basho_bench with identical configurations for both hierdis and eredis. Except for utilizing their respective basho_bench drivers. The GET/PUT balance was even, and the concurrency was set to 4 to match the number of logical cores on the CPU.

redis-server was flushed and restarted before each test run, and disk-persistence was disabled for each run as well.

The respective configurations and complete results can be found here hierdis_vs_eredis.zip

#Simple. Right?

(The MIT License)

Copyright (c) 2013 Nathan Aschbacher

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.

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