Event Networking for Go

evio is an event driven networking framework that is fast and small. It makes direct epoll and kqueue syscalls rather than the standard Go net package. It works in a similar manner as libuv and libevent.

The goal of this project is to create a server framework for Go that performs on par with Redis and Haproxy for packet handling, but without having to interop with Cgo. My hope is to use this as a foundation for Tile38 and other projects.

Features

• Very fast single-threaded design
• Simple API. Only one entrypoint and eight events
• Low memory usage
• Supports tcp4, tcp6, and unix sockets
• Allows multiple network binding on the same event loop
• Has a flexible ticker event
• Support for non-epoll/kqueue operating systems by simulating events with the net package.

Getting Started

Installing

To start using evio, install Go and run go get:

$ go get -u github.com/tidwall/evio

This will retrieve the library.

Usage

There's only one function:

func Serve(events Events, addr ...string) error

The Events type has the following events:

// Events represents server events
type Events struct {
	// Serving fires when the server can accept connections.
	// The wake parameter is a goroutine-safe function that triggers
	// a Data event (with a nil `in` parameter) for the specified id.
	Serving func(wake func(id int) bool) (action Action)
	// Opened fires when a new connection has opened.
	// Use the out return value to write data to the connection.
	Opened func(id int, addr string) (out []byte, opts Options, action Action)
	// Opened fires when a connection is closed
	Closed func(id int) (action Action)
	// Detached fires when a connection has been previously detached.
	Detached func(id int, conn io.ReadWriteCloser) (action Action)
	// Data fires when a connection sends the server data.
	// Use the out return value to write data to the connection.
	Data func(id int, in []byte) (out []byte, action Action)
	// Prewrite fires prior to every write attempt.
	// The amount parameter is the number of bytes that will be attempted
	// to be written to the connection.
	Prewrite func(id int, amount int) (action Action)
	// Postwrite fires immediately after every write attempt.
	// The amount parameter is the number of bytes that was written to the
	// connection.
	// The remaining parameter is the number of bytes that still remain in
	// the buffer scheduled to be written.
	Postwrite func(id int, amount, remaining int) (action Action)
	// Tick fires immediately after the server starts and will fire again
	// following the duration specified by the delay return value.
	Tick func() (delay time.Duration, action Action)
}

• All events are executed in the same thread as the Serve call.
• handle, accept, and closed events have an id param which is a unique number assigned to the client socket.
• data represents a network packet.
• ctx is a user-defined context or nil.
• wake is a function that when called will trigger the handle event with zero data for the specified id. It can be called safely from other Goroutines.
• ticker is an event that fires between 1 and 60 times a second, depending on the packet traffic.

Example

Please check out the examples subdirectory for a simplified redis clone and an echo server.

Here's a basic echo server:

package main

import (
	"flag"
	"fmt"
	"log"

	"github.com/tidwall/shiny"
)

var shutdown bool
var started bool
var port int

func main() {
	flag.IntVar(&port, "port", 9999, "server port")
	flag.Parse()
	log.Fatal(shiny.Serve("tcp", fmt.Sprintf(":%d", port),
		handle, accept, closed, ticker, nil))
}

// handle - the incoming client socket data.
func handle(id int, data []byte, ctx interface{}) (send []byte, keepopen bool) {
	if shutdown {
		return nil, false
	}
	keepopen = true
	if string(data) == "shutdown\r\n" {
		shutdown = true
	} else if string(data) == "quit\r\n" {
		keepopen = false
	}
	return data, keepopen
}

// accept - a new client socket has opened.
// 'wake' is a function that when called will fire a 'handle' event
// for the specified ID, and is goroutine-safe.
func accept(id int, addr string, wake func(), ctx interface{}) (send []byte, keepopen bool) {
	if shutdown {
		return nil, false
	}
	// this is a good place to create a user-defined socket context.
	return []byte(
		"Welcome to the echo server!\n" +
			"Enter 'quit' to close your connection or " +
			"'shutdown' to close the server.\n"), true
}

// closed - a client socket has closed
func closed(id int, err error, ctx interface{}) {
	// teardown the socket context here
}

// ticker - a ticker that fires between 1 and 1/20 of a second
// depending on the traffic.
func ticker(ctx interface{}) (keepserving bool) {
	if shutdown {
		// do server teardown here
		return false
	}
	if !started {
		fmt.Printf("echo server started on port %d\n", port)
		started = true
	}
	// perform various non-socket io related operations here
	return true
}

Run the example:

$ go run examples/echo-server/main.go

Connect to the server:

$ telnet localhost 9999

Performance

The benchmarks below use pipelining which allows for combining multiple Redis commands into a single packet.

Redis

$ redis-server --port 6379 --appendonly no

redis-benchmark -p 6379 -t ping,set,get -q -P 128
PING_INLINE: 961538.44 requests per second
PING_BULK: 1960784.38 requests per second
SET: 943396.25 requests per second
GET: 1369863.00 requests per second

Shiny

$ go run examples/redis-server/main.go --port 6380 --appendonly no

redis-benchmark -p 6380 -t ping,set,get -q -P 128
PING_INLINE: 3846153.75 requests per second
PING_BULK: 4166666.75 requests per second
SET: 3703703.50 requests per second
GET: 3846153.75 requests per second

Running on a MacBook Pro 15" 2.8 GHz Intel Core i7 using Go 1.7

Contact

Josh Baker @tidwall

License

Shiny source code is available under the MIT License.