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RedisPipe

RedisPipe – is a client for redis that uses "implicit pipelining" for highest performance.

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Highlights

Introduction

https://redis.io/topics/pipelining

Pipelining improves the maximum throughput that redis can serve, and reduces CPU usage both on redis server and on the client side. Mostly it comes from saving system CPU consumption.

But it is not always possible to use pipelining explicitly: usually there are dozens of concurrent goroutines, each sends just one request at a time. To handle the usual workload, pipelining has to be implicit.

"Implicit pipelining" is used in many drivers for other languages:

At the moment this connector were created there was no such connector for Golang. All known Golang redis connectors use a connection-per-request model with a connection pool, and provide only explicit pipelining.

This connector was created as implicitly pipelined from the ground up to achieve maximum performance in a highly concurrent environment. It writes all requests to single connection to redis, and continuously reads answers from another goroutine.

Note that it trades a bit of latency for throughput, and therefore could be not optimal for low-concurrent low-request-per-second usage. Write loop latency is configurable as WritePause parameter in connection options, and could be disabled at all, or increased to higher values (150µs is the value used in production, 50µs is default value, -1 disables write pause). Implicit runtime latency for switching goroutines still remains, however, and could not be removed.

Performance

Single redis

goos: linux
goarch: amd64
pkg: github.com/joomcode/redispipe/rediscluster
cpu: Intel(R) Core(TM) i7-10750H CPU @ 2.60GHz
BenchmarkSerialGetSet/radix_pause0-12              17691             63132 ns/op              68 B/op          4 allocs/op
BenchmarkSerialGetSet/redigo-12            19519             60064 ns/op             239 B/op         13 allocs/op
BenchmarkSerialGetSet/redispipe-12           504           2661790 ns/op             290 B/op         12 allocs/op
BenchmarkSerialGetSet/redispipe_pause0-12                  13669             84925 ns/op             208 B/op         12 allocs/op
BenchmarkParallelGetSet/radix-12                          621036              1817 ns/op              78 B/op          4 allocs/op
BenchmarkParallelGetSet/redigo-12                           7466            153584 ns/op            4008 B/op         20 allocs/op
BenchmarkParallelGetSet/redispipe-12                      665428              1599 ns/op             231 B/op         12 allocs/op

You can see a couple of things:

That is true: redispipe trades latency for throughput. Every single request has additional latency for hidden batching in a connector. But thanks to batching, more requests can be sent to redis and answered by redis in an interval of time.

SerialGetSet/redispipe_pause0 shows single-threaded results with disabled additional latency for "batching" (WritePause: -1). This way redispipe is quite close to other connectors in performance, though there is still small overhead of internal design. But I would not recommend disable batching (unless your use case is single threaded), because it increases CPU usage under highly concurrent load both on client and on redis-server.

To be honestly, github.com/mediocregopher/radix/v3 is also able to perform implicit pipelining and does it by default. Therefore it is almost as fast as redispipe in ParallelGetSet. SerialGetSet is tested with disabled pipelining, because otherwise it will be as slow as redispipe without pause0.

Cluster

go test -count 1 -tags=debugredis -run FooBar -bench . -benchmem -benchtime 5s ./rediscluster
goos: linux
goarch: amd64
pkg: github.com/joomcode/redispipe/rediscluster
BenchmarkSerialGetSet/radixv2-8           200000    53585 ns/op   1007 B/op   31 allocs/op
BenchmarkSerialGetSet/redigo-8            200000    40705 ns/op    246 B/op   12 allocs/op
BenchmarkSerialGetSet/redispipe-8          30000   279838 ns/op    220 B/op   12 allocs/op
BenchmarkSerialGetSet/redispipe_pause0-8  200000    56356 ns/op    216 B/op   12 allocs/op
BenchmarkParallelGetSet/radixv2-8        1000000     9245 ns/op   1268 B/op   32 allocs/op
BenchmarkParallelGetSet/redigo-8         1000000     6886 ns/op    399 B/op   13 allocs/op
BenchmarkParallelGetSet/redispipe-8      5000000     1636 ns/op    219 B/op   12 allocs/op

With cluster configuration, internal cluster meta-info management adds additional overhead inside of the Go process. And redispipe/rediscluster attempts to provide almost lockless cluster info handling on the way of request execution.

While redigo is almost as fast in Parallel tests, it also happens to be limited by Redis's CPU usage (three redis processes eats whole 3 cpu cores). It uses a huge number of connections, and it is not trivial to recognize non-default setting that should be set to achieve this result (both KeepAlive and AliveTime should be set as high as 128). ( github.com/chasex/redis-go-cluster is used).

Each Redis uses less than 60% CPU core when redispipe is used, despite serving more requests.

Practice

In practice, performance gain is lesser, because your application does other useful work aside from sending requests to Redis. But gain is still noticeable. At our setup, we have around 10-15% less CPU usage on Redis (ie 50%CPU->35%CPU), and 5-10% improvement on the client side. WritePause is usually set to higher value (150µs) than default.

Limitations

Installation

Usage

Both redisconn.Connect and rediscluster.NewCluster creates implementations of redis.Sender. redis.Sender provides asynchronous api for sending request/requests/transactions. That api accepts redis.Future interface implementations as an argument and fullfills it asynchronously. Usually you don't need to provide your own redis.Future implementation, but rather use synchronous wrappers.

To use convenient synchronous api, one should wrap "sender" with one of wrappers:

Types accepted as command arguments: nil, []byte, string, int (and all other integer types), float64, float32, bool. All arguments are converted to redis bulk strings as usual (ie string and bytes - as is; numbers - in decimal notation). bool converted as "0/1", nil converted to empty string.

In difference to other redis packages, no custom types are used for request results. Results are de-serialized into plain go types and are returned as interface{}:

redisgo
plain stringstring
bulk string[]byte
integerint64
array[]interface{}
errorerror (*errorx.Error)

IO, connection, and other errors are not returned separately, but as result (and has same *errorx.Error underlying type).

package redispipe_test

import (
	"context"
	"fmt"
	"log"

	"github.com/joomcode/redispipe/redis"
	"github.com/joomcode/redispipe/rediscluster"
	"github.com/joomcode/redispipe/redisconn"
)

const databaseno = 0
const password = ""

var myhandle interface{} = nil

func Example_usage() {
	ctx := context.Background()
	cluster := false

	SingleRedis := func(ctx context.Context) (redis.Sender, error) {
		opts := redisconn.Opts{
			DB:       databaseno,
			Password: password,
			Logger:   redisconn.NoopLogger{}, // shut up logging. Could be your custom implementation.
			Handle:   myhandle,               // custom data, useful for custom logging
			// Other parameters (usually, no need to change)
			// IOTimeout, DialTimeout, ReconnectTimeout, TCPKeepAlive, Concurrency, WritePause, Async
		}
		conn, err := redisconn.Connect(ctx, "127.0.0.1:6379", opts)
		return conn, err
	}

	ClusterRedis := func(ctx context.Context) (redis.Sender, error) {
		opts := rediscluster.Opts{
			HostOpts: redisconn.Opts{
				// No DB
				Password: password,
				// Usually, no need for special logger
			},
			Name:   "mycluster",               // name of a cluster
			Logger: rediscluster.NoopLogger{}, // shut up logging. Could be your custom implementation.
			Handle: myhandle,                  // custom data, useful for custom logging
			// Other parameters (usually, no need to change):
			// ConnsPerHost, ConnHostPolicy, CheckInterval, MovedRetries, WaitToMigrate, RoundRobinSeed,
		}
		addresses := []string{"127.0.0.1:20001"} // one or more of cluster addresses
		cluster, err := rediscluster.NewCluster(ctx, addresses, opts)
		return cluster, err
	}

	var sender redis.Sender
	var err error
	if cluster {
		sender, err = ClusterRedis(ctx)
	} else {
		sender, err = SingleRedis(ctx)
	}
	if err != nil {
		log.Fatal(err)
	}
	defer sender.Close()

	sync := redis.SyncCtx{sender} // wrapper for synchronous api

	res := sync.Do(ctx, "SET", "key", "ho")
	if err := redis.AsError(res); err != nil {
		log.Fatal(err)
	}
	fmt.Printf("result: %q\n", res)

	res = sync.Do(ctx, "GET", "key")
	if err := redis.AsError(res); err != nil {
		log.Fatal(err)
	}
	fmt.Printf("result: %q\n", res)

	res = sync.Send(ctx, redis.Req("HMSET", "hashkey", "field1", "val1", "field2", "val2"))
	if err := redis.AsError(res); err != nil {
		log.Fatal(err)
	}

	res = sync.Send(ctx, redis.Req("HMGET", "hashkey", "field1", "field2", "field3"))
	if err := redis.AsError(res); err != nil {
		log.Fatal(err)
	}
	for i, v := range res.([]interface{}) {
		fmt.Printf("%d: %T %q\n", i, v, v)
	}

	res = sync.Send(ctx, redis.Req("HMGET", "key", "field1"))
	if err := redis.AsError(res); err != nil {
		if rerr := redis.AsErrorx(res); rerr != nil && rerr.IsOfType(redis.ErrResult) {
			fmt.Printf("expected error: %v\n", rerr)
		} else {
			fmt.Printf("unexpected error: %v\n", err)
		}
	} else {
		fmt.Printf("unexpected missed error\n")
	}

	results := sync.SendMany(ctx, []redis.Request{
		redis.Req("GET", "key"),
		redis.Req("HMGET", "hashkey", "field1", "field3"),
	})
	// results is []interface{}, each element is result for corresponding request
	for i, res := range results {
		fmt.Printf("result[%d]: %T %q\n", i, res, res)
	}

	results, err = sync.SendTransaction(ctx, []redis.Request{
		redis.Req("SET", "a{x}", "b"),
		redis.Req("SET", "b{x}", 0),
		redis.Req("INCRBY", "b{x}", 3),
	})
	if err != nil {
		log.Fatal(err)
	}
	for i, res := range results {
		fmt.Printf("tresult[%d]: %T %q\n", i, res, res)
	}

	// Output:
	// result: "OK"
	// result: "ho"
	// 0: []uint8 "val1"
	// 1: []uint8 "val2"
	// 2: <nil> %!q(<nil>)
	// expected error: WRONGTYPE Operation against a key holding the wrong kind of value (ErrResult {connection: *redisconn.Connection{addr: 127.0.0.1:6379}})
	// result[0]: []uint8 "ho"
	// result[1]: []interface {} ["val1" <nil>]
	// tresult[0]: string "OK"
	// tresult[1]: string "OK"
	// tresult[2]: int64 '\x03'
}

Contributing

License

MIT License