evio is an event loop networking framework that is fast and small. It makes direct epoll and kqueue syscalls rather than using the standard Go net package, and 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. It was built to be the foundation for Tile38 and a future L7 proxy for Go.
Please note: Evio should not be considered as a drop-in replacement for the standard Go net or net/http packages.
- Fast single-threaded or multithreaded event loop
- Built-in load balancing options
- Simple API
- Low memory usage
- Supports tcp, udp, and unix sockets
- Allows multiple network binding on the same event loop
- Flexible ticker event
- Fallback for non-epoll/kqueue operating systems by simulating events with the net package
- SO_REUSEPORT socket option
To start using evio, install Go and run go get:
$ go get -u github.com/tidwall/evioThis will retrieve the library.
Starting a server is easy with evio. Just set up your events and pass them to the Serve function along with the binding address(es). Each connections is represented as an evio.Conn object that is passed to various events to differentiate the clients. At any point you can close a client or shutdown the server by return a Close or Shutdown action from an event.
Example echo server that binds to port 5000:
package main
import "github.com/tidwall/evio"
func main() {
var events evio.Events
events.Data = func(c evio.Conn, in []byte) (out []byte, action evio.Action) {
out = in
return
}
if err := evio.Serve(events, "tcp://localhost:5000"); err != nil {
panic(err.Error())
}
}Here the only event being used is Data, which fires when the server receives input data from a client.
The exact same input data is then passed through the output return value, which is then sent back to the client.
Connect to the echo server:
$ telnet localhost 5000The event type has a bunch of handy events:
Servingfires when the server is ready to accept new connections.Openedfires when a connection has opened.Closedfires when a connection has closed.Detachfires when a connection has been detached using theDetachreturn action.Datafires when the server receives new data from a connection.Tickfires immediately after the server starts and will fire again after a specified interval.
A server can bind to multiple addresses and share the same event loop.
evio.Serve(events, "tcp://192.168.0.10:5000", "unix://socket")The Tick event fires ticks at a specified interval.
The first tick fires immediately after the Serving events.
events.Tick = func() (delay time.Duration, action Action){
log.Printf("tick")
delay = time.Second
return
}The Serve function can bind to UDP addresses.
- All incoming and outgoing packets are not buffered and sent individually.
- The
OpenedandClosedevents are not availble for UDP sockets, only theDataevent.
The events.NumLoops options sets the number of loops to use for the server.
A value greater than 1 will effectively make the server multithreaded for multi-core machines.
Which means you must take care when synchonizing memory between event callbacks.
Setting to 0 or 1 will run the server as single-threaded.
Setting to -1 will automatically assign this value equal to runtime.NumProcs().
The events.LoadBalance options sets the load balancing method.
Load balancing is always a best effort to attempt to distribute the incoming connections between multiple loops.
This option is only available when events.NumLoops is set.
Randomrequests that connections are randomly distributed.RoundRobinrequests that connections are distributed to a loop in a round-robin fashion.LeastConnectionsassigns the next accepted connection to the loop with the least number of active connections.
Servers can utilize the SO_REUSEPORT option which allows multiple sockets on the same host to bind to the same port.
Just provide reuseport=true to an address:
evio.Serve(events, "tcp://0.0.0.0:1234?reuseport=true"))Please check out the examples subdirectory for a simplified redis clone, an echo server, and a very basic http server.
To run an example:
$ go run examples/http-server/main.go
$ go run examples/redis-server/main.go
$ go run examples/echo-server/main.goThese benchmarks were run on an ec2 c4.xlarge instance in single-threaded mode (GOMAXPROC=1) over Ipv4 localhost. Check out benchmarks for more info.
Josh Baker @tidwall
evio source code is available under the MIT License.
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