redis翻译_redis管道

Redis is a TCP server using the client-server model and what is called a Request/Response protocol.

So for instance a four commands sequence is something like this:

• Client: INCR X
• Server: 1
• Client: INCR X
• Server: 2
• Client: INCR X
• Server: 3
• Client: INCR X
• Server: 4

Redis Pipelining

A Request/Response server can be implemented so that it is able to process new requests even if the client didn‘t already read the old responses. This way it is possible to send multiple commands to the server without waiting for the replies at all, and finally read the replies in a single step.

$ (printf "PING\r\nPING\r\nPING\r\n"; sleep 1) | nc localhost 6379
+PONG
+PONG
+PONG

This time we are not paying the cost of RTT for every call, but just one time for the three commands

• Client: INCR X
• Client: INCR X
• Client: INCR X
• Client: INCR X
• Server: 1
• Server: 2
• Server: 3
• Server: 4

Some benchmark

In the following benchmark we‘ll use the Redis Ruby client, supporting pipelining, to test the speed improvement due to pipelining:

require ‘rubygems‘
require ‘redis‘

def bench(descr)
    start = Time.now
    yield
    puts "#{descr} #{Time.now-start} seconds"
end

def without_pipelining
    r = Redis.new
    10000.times {
        r.ping
    }
end

def with_pipelining
    r = Redis.new
    r.pipelined {
        10000.times {
            r.ping
        }
    }
end

bench("without pipelining") {
    without_pipelining
}
bench("with pipelining") {
    with_pipelining
}

Running the above simple script will provide the following figures in my Mac OS X system, running over the loopback interface, where pipelining will provide the smallest improvement as the RTT is already pretty low:

without pipelining 1.185238 seconds
with pipelining 0.250783 seconds

As you can see, using pipelining, we improved the transfer by a factor of five.

Pipelining VS Scripting

Using Redis scripting (available in Redis version 2.6 or greater) a number of use cases for pipelining can be addressed more efficiently using scripts that perform a lot of the work needed at the server side. A big advantage of scripting is that it is able to both read and write data with minimal latency, making operations like read, compute, write very fast (pipelining can‘t help in this scenario since the client needs the reply of the read command before it can call the write command).