Doc for gnet v1

🎉 Getting Started

Prerequisites

gnet requires Go 1.9 or later.

Installation

go get -u github.com/panjf2000/gnet

gnet is available as a Go module, with Go 1.11 Modules support (Go 1.11+), just simply import "github.com/panjf2000/gnet" in your source code and go [build|run|test] will download the necessary dependencies automatically.

Usage Examples

The detailed documentation is located here: docs of gnet, but let's pass through the brief instructions first.

It is easy to create a network server with gnet. All you have to do is just to make your implementation of gnet.EventHandler interface and register your event-handler functions to it, then pass it to the gnet.Serve function along with the binding address(es). Each connection is represented as a gnet.Conn interface that is passed to various events to differentiate the clients. At any point you can close a connection or shutdown the server by return a Close or Shutdown action from an event function.

The simplest example to get you started playing with gnet would be the echo server. So here you are, a simplest echo server upon gnet that is listening on port 9000:

Echo server without blocking logic

Old version(<=v1.0.0-rc.4) 
package main


import (
    "log"


    "github.com/panjf2000/gnet"
)


type echoServer struct {
    gnet.EventServer
}


func (es *echoServer) React(c gnet.Conn) (out []byte, action gnet.Action) {
    out = c.Read()
    c.ResetBuffer()
    return
}


func main() {
    echo := new(echoServer)
    log.Fatal(gnet.Serve(echo, "tcp://:9000", gnet.WithMulticore(true)))
}
package main


import (
    "log"


    "github.com/panjf2000/gnet"
)


type echoServer struct {
    gnet.EventServer
}


func (es *echoServer) React(frame []byte, c gnet.Conn) (out []byte, action gnet.Action) {
    out = frame
    return
}


func main() {
    echo := new(echoServer)
    log.Fatal(gnet.Serve(echo, "tcp://:9000", gnet.WithMulticore(true)))
}

As you can see, this example of echo server only sets up the EventHandler.React function where you commonly write your main business code and it will be called once the server receives input data from a client. What you should know is that the input parameter: frame is a complete packet which has been decoded by the codec, as a general rule, you should implement the gnet codec interface as the business codec to packet and unpacket TCP stream, but if you don't, your gnet server is going to work with the default codec under the acquiescence, which means all data inculding latest data and previous data in buffer will be stored in the input parameter: frame when EventHandler.React is being triggered. The output data will be then encoded and sent back to that client by assigning the out variable and returning it after your business code finish processing data(in this case, it just echo the data back).

Echo server with blocking logic

Old version(<=v1.0.0-rc.4) 
package main


import (
    "log"
    "time"


    "github.com/panjf2000/gnet"
    "github.com/panjf2000/gnet/pool/goroutine"
)


type echoServer struct {
    gnet.EventServer
    pool *goroutine.Pool
}


func (es *echoServer) React(c gnet.Conn) (out []byte, action gnet.Action) {
    data := append([]byte{}, c.Read()...)
    c.ResetBuffer()


    // Use ants pool to unblock the event-loop.
    _ = es.pool.Submit(func() {
        time.Sleep(1 * time.Second)
        c.AsyncWrite(data)
    })


    return
}


func main() {
    p := goroutine.Default()
    defer p.Release()


    echo := &echoServer{pool: p}
    log.Fatal(gnet.Serve(echo, "tcp://:9000", gnet.WithMulticore(true)))
}
package main


import (
    "log"
    "time"


    "github.com/panjf2000/gnet"
    "github.com/panjf2000/gnet/pool/goroutine"
)


type echoServer struct {
    gnet.EventServer
    pool *goroutine.Pool
}


func (es *echoServer) React(frame []byte, c gnet.Conn) (out []byte, action gnet.Action) {
    data := append([]byte{}, frame...)


    // Use ants pool to unblock the event-loop.
    _ = es.pool.Submit(func() {
        time.Sleep(1 * time.Second)
        c.AsyncWrite(data)
    })


    return
}


func main() {
    p := goroutine.Default()
    defer p.Release()


    echo := &echoServer{pool: p}
    log.Fatal(gnet.Serve(echo, "tcp://:9000", gnet.WithMulticore(true)))
}

Like I said in the 『Multiple Reactors + Goroutine Pool』section, if there are blocking code in your business logic, then you ought to turn them into non-blocking code in any way, for instance, you can wrap them into a goroutine, but it will result in a massive amount of goroutines if massive traffic is passing through your server so I would suggest you utilize a goroutine pool like ants to manage those goroutines and reduce the cost of system resources.

All gnet examples:

I/O Events

Current supported I/O events in gnet:

  • EventHandler.OnInitComplete fires when the server has been initialized and ready to accept new connections.
  • EventHandler.OnOpened fires once a connection has been opened.
  • EventHandler.OnClosed fires after a connection has been closed.
  • EventHandler.React fires when the server receives inbound data from a socket/connection. (usually it is where you write the code of business logic)
  • EventHandler.Tick fires right after the server starts and then fires every specified interval.
  • EventHandler.PreWrite fires just before any data has been written to client.

poll_opt mode

By default, gnet utilizes the standard package golang.org/x/sys/unix to implement pollers with epoll or kqueue, where a HASH MAP of fd->conn is introduced to help retrieve connections by file descriptors returned from pollers, but now the user can run go build with build tags poll_opt, like this: go build -tags=poll_opt, and gnet then switch to the optimized implementations of pollers that invoke the system calls of epoll or kqueue directly and add file descriptors to the interest list along with storing the corresponding connection pointers into epoll_data or kevent, in which case gnet can get rid of the HASH MAP of fd->conn and regain each connection pointer by the conversion of void* pointer in the I/O event-looping. In theory, it ought to achieve a higher performance with this optimization.

See #230 for code details.

Ticker

The EventHandler.Tick event fires ticks at a specified interval. The first tick fires right after the gnet server starts up and if you intend to set up a ticker event, don't forget to pass an option: gnet.WithTicker(true) to gnet.Serve.

events.Tick = func() (delay time.Duration, action Action){
    log.Printf("tick")
    delay = time.Second
    return
}

UDP

gnet supports UDP protocol so the gnet.Serve method can bind to UDP addresses.

  • All incoming and outgoing packets will not be buffered but read and sent directly, which means all functions of gnet.Conn that manipulate the internal buffers are not available; users should use the frame []byte from the gnet.React(frame []byte, c gnet.Conn) as the UDP packet instead calling functions of gnet.Conn, like c.Read(), c.ResetBuffer(), c.BufferLength() and so on, to process data.
  • The EventHandler.OnOpened and EventHandler.OnClosed events are not available for UDP sockets, only the React event.
  • The UDP equivalents of AsyncWrite([]byte) in TCP is SendTo([]byte).

Unix Domain Socket

gnet also supports UDS(Unix Domain Socket), just pass the UDS addresses like "unix://xxx" to the gnet.Serve method and you could play with it.

It is nothing different from making use of TCP when doing stuff with UDS, so the gnet UDS servers are able to leverage all event functions which are available under TCP protocol.

Multi-threads

The gnet.WithMulticore(true) indicates whether the server will be effectively created with multi-cores, if so, then you must take care of synchronizing memory between all event callbacks, otherwise, it will run the server with a single thread. The number of threads in the server will be automatically assigned to the value of runtime.NumCPU().

Load Balancing

gnet currently supports three load balancing algorithms: Round-Robin, Source-Addr-Hash and Least-Connections, you are able to decide which algorithm to use by passing the functional option LB (RoundRobin/LeastConnections/SourceAddrHash) to gnet.Serve.

If the load balancing algorithm is not specified explicitly, gnet will use Round-Robin by default.

SO_REUSEPORT

gnet server is able to utilize the SO_REUSEPORT option which allows multiple sockets on the same host to bind to the same port and the OS kernel takes care of the load balancing for you, it wakes one socket per connect event coming to resolved the thundering herd.

By default, gnet is not going to be haunted by the thundering herd under its networking model:『multiple reactors』which gets only one main reactor to listen on "address:port" and accept new sockets. So this SO_REUSEPORT option is trivial in gnet but note that it will fall back to the old networking model of evio when you enable the SO_REUSEPORT option.

Just use functional options to set up SO_REUSEPORT and you can enjoy this feature:

gnet.Serve(events, "tcp://:9000", gnet.WithMulticore(true), gnet.WithReusePort(true)))

Multiple built-in codecs for TCP stream

There are multiple built-in codecs in gnet which allow you to encode/decode frames into/from TCP stream.

So far gnet has four kinds of built-in codecs: LineBasedFrameCodec, DelimiterBasedFrameCodec, FixedLengthFrameCodec and LengthFieldBasedFrameCodec, which generally meets most scenarios, but still gnet allows users to customize their own codecs in their gnet servers by implementing the interface gnet.ICodec and replacing the default codec in gnet with customized codec via functional options.

Here is an example with codec, showing you how to leverage codec to encode/decode network frames into/from TCP stream.

📊 Performance

Benchmarks on TechEmpower

# Hardware Environment
* 28 HT Cores Intel(R) Xeon(R) Gold 5120 CPU @ 3.20GHz
* 32GB RAM
* Dedicated Cisco 10-gigabit Ethernet switch
* Debian 12 "bookworm"
* Go1.19.x linux/amd64

This is a leaderboard of the top 50 out of 486 frameworks that encompass various programming languages worldwide, in which gnet is ranked first.

This is the full framework ranking of Go and gnet tops all the other frameworks, which makes gnet the fastest networking framework in Go.

To see the full ranking list, visit TechEmpower Benchmark Round 22.

Contrasts to the similar networking libraries

On Linux (epoll)

Test Environment

# Machine information
        OS : Ubuntu 20.04/x86_64
       CPU : 8 CPU cores, AMD EPYC 7K62 48-Core Processor
    Memory : 16.0 GiB


# Go version and settings
Go Version : go1.17.2 linux/amd64
GOMAXPROCS : 8


# Benchmark parameters
TCP connections : 1000/2000/5000/10000
Packet size     : 512/1024/2048/4096/8192/16384/32768/65536 bytes
Test duration   : 15s

Echo benchmark

On MacOS (kqueue)

Test Environment

# Machine information
        OS : MacOS Big Sur/x86_64
       CPU : 6 CPU cores, Intel(R) Core(TM) i7-9750H CPU @ 2.60GHz
    Memory : 16.0 GiB


# Go version and settings
Go Version : go1.16.5 darwin/amd64
GOMAXPROCS : 12


# Benchmark parameters
TCP connections : 300/400/500/600/700
Packet size     : 512/1024/2048/4096/8192 bytes
Test duration   : 15s

Echo benchmark

️🚨 License

Source code in gnet is available under the MIT License.

👏 Contributors

Please read the Contributing Guidelines before opening a PR and thank you to all the developers who already made contributions to gnet!

🙏 Acknowledgments

⚓ Relevant Articles

🎡 Use cases

The following companies/organizations use gnet as the underlying network service in production.

          

If your projects are also using gnet, feel free to open a pull request refreshing this list of use cases.

💰 Backers

Support us with a monthly donation and help us continue our activities.

💎 Sponsors

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☕️ Buy me a coffee

Please be sure to leave your name, Github account or other social media accounts when you donate by the following means so that I can add it to the list of donors as a token of my appreciation.

💴 Patrons

Patrick Othmer  Jimmy  ChenZhen  Mai Yang  王开帅  Unger Alejandro  Swaggadan Weng Wei

🔑 JetBrains OS licenses

gnet had been being developed with GoLand IDE under the free JetBrains Open Source license(s) granted by JetBrains s.r.o., hence I would like to express my thanks here.

🔋 Sponsorship

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