hiredis-rb

Ruby extension that wraps hiredis. Both the synchronous connection API and a separate protocol reader are supported. It is primarily intended to speed up parsing multi bulk replies.

Install with Rubygems:

gem install hiredis

Hiredis can be used as standalone library, or be used together with redis-rb. The latter adds in support for hiredis in 2.2.

To use hiredis from redis-rb, it needs to be available in Ruby's load path. Using Bundler, this comes down to adding the following lines:

gem "hiredis", "~> 0.6.0"
gem "redis", ">= 3.2.0"

To use hiredis with redis-rb, you need to require redis/connection/hiredis before creating a new connection. This makes sure that hiredis will be used instead of the pure Ruby connection code and protocol parser. Doing so in the Gemfile is done by adding a :require option to the line adding the redis-rb dependency:

gem "redis", ">= 3.2.0", :require => ["redis", "redis/connection/hiredis"]

You can use Redis normally, as you would with the pure Ruby version.

A connection to Redis can be opened by creating an instance of Hiredis::Connection and calling #connect:

conn = Hiredis::Connection.new
conn.connect("127.0.0.1", 6379)

Commands can be written to Redis by calling #write with an array of arguments. You can call write more than once, resulting in a pipeline of commands.

conn.write ["SET", "speed", "awesome"]
conn.write ["GET", "speed"]

After commands are written, use #read to receive the subsequent replies. Make sure not to call #read more than you have replies to read, or the connection will block indefinitely. You can use this feature to implement a subscriber (for Redis Pub/Sub).

>> conn.read
=> "OK"

>> conn.read
=> "awesome"

When the connection was closed by the server, an error of the type Hiredis::Connection::EOFError will be raised. For all I/O related errors, the Ruby built-in Errno::XYZ errors will be raised. All other errors (such as a protocol error) result in a RuntimeError.

You can skip loading everything and just load Hiredis::Connection by requiring hiredis/connection.

Only using hiredis for the reply parser can be very useful in scenarios where the I/O is already handled by another component (such as EventMachine).

You can skip loading everything and just load Hiredis::Reader by requiring hiredis/reader.

Use #feed on an instance of Hiredis::Reader to feed the stream parser with new data. Use #read to get the parsed replies one by one:

>> reader = Hiredis::Reader.new
>> reader.feed("*2\r\n$7\r\nawesome\r\n$5\r\narray\r\n")
>> reader.gets
=> ["awesome", "array"]

These numbers were generated by running benchmark/throughput.rb against ruby 1.9.2p180 (2011-02-18 revision 30909) [x86_64-darwin10.6.0]. The benchmark compares redis-rb with the Ruby connection and protocol code against redis-rb with hiredis to handle I/O and reply parsing.

For simple line or bulk replies, the throughput improvement is insignificant, while the larger multi bulk responses will have a noticeable higher throughput.

                                                        user     system      total        real
redis-rb:  1x SET pipeline, 10000 times             0.260000   0.140000   0.400000 (  0.726216)
 hiredis:  1x SET pipeline, 10000 times             0.170000   0.130000   0.300000 (  0.602332)
redis-rb: 10x SET pipeline, 10000 times             1.550000   0.660000   2.210000 (  2.231505)
 hiredis: 10x SET pipeline, 10000 times             0.400000   0.140000   0.540000 (  0.995266)

redis-rb:  1x GET pipeline, 10000 times             0.270000   0.150000   0.420000 (  0.730322)
 hiredis:  1x GET pipeline, 10000 times             0.170000   0.130000   0.300000 (  0.604060)
redis-rb: 10x GET pipeline, 10000 times             1.480000   0.640000   2.120000 (  2.122215)
 hiredis: 10x GET pipeline, 10000 times             0.380000   0.130000   0.510000 (  0.925731)

redis-rb:  1x LPUSH pipeline, 10000 times           0.260000   0.150000   0.410000 (  0.725292)
 hiredis:  1x LPUSH pipeline, 10000 times           0.160000   0.130000   0.290000 (  0.592466)
redis-rb: 10x LPUSH pipeline, 10000 times           1.540000   0.660000   2.200000 (  2.202709)
 hiredis: 10x LPUSH pipeline, 10000 times           0.360000   0.130000   0.490000 (  0.940361)

redis-rb:  1x LRANGE(100) pipeline, 1000 times      0.240000   0.020000   0.260000 (  0.307504)
 hiredis:  1x LRANGE(100) pipeline, 1000 times      0.050000   0.020000   0.070000 (  0.100293)

redis-rb:  1x LRANGE(1000) pipeline, 1000 times     2.100000   0.030000   2.130000 (  2.353551)
 hiredis:  1x LRANGE(1000) pipeline, 1000 times     0.320000   0.030000   0.350000 (  0.472789)

This code is released under the BSD license, after the license of hiredis.