reflexionhealth/endless

Zero downtime restarts for golang HTTP and HTTPS servers.
A fork of fvbock/endless, frankenstein'd together with ideas from goagain, and caddy.

Link to the normal documentation

Default Timeouts & MaxHeaderBytes

There are three variables exported by the package that control the values set for DefaultReadTimeOut, DefaultWriteTimeOut, and MaxHeaderBytes on the inner http.Server:

DefaultReadTimeOut    time.Duration
DefaultWriteTimeOut   time.Duration
DefaultMaxHeaderBytes int

The endless default behaviour is to use the same defaults defined in net/http.

These have impact on endless by potentially not letting the parent process die until all connections are handled/finished.

Shutdown Timeout

To deal with hanging requests on the parent, the parent server will exit the main loop 60 seconds after receiving the shutdown signal from the forked child process. Still running requests are terminated on exit. This behaviour can be controlled by another exported variable:

DefaultShutdownTimeout time.Duration

The default is 60 seconds. When set to -1 requests will not be terminated, instead relying on the Read and Write timeouts.

Signals

The endless server will listen for the following signals: syscall.SIGHUP, syscall.SIGUSR1, syscall.SIGUSR2, syscall.SIGINT, syscall.SIGTERM, and syscall.SIGTSTP:

SIGHUP currently triggers a fork/restart (TODO: eventually, this should be a reload)
SIGUSR2 will trigger a fork/restart
SIGINT and SIGTERM will trigger a shutdown of the server (it will finish running requests)
SIGQUIT triggers a much less graceful shutdown

Usage

import "github.com/reflexionhealth/endless"

and then replacing http.ListenAndServe with endless.ListenAndServe or http.ListenAndServeTLS with endless.ListenAndServeTLS

err := endless.ListenAndServe("localhost:4242", handler)

After starting your server you can make some changes, build, and send SIGHUP to the running process and it will finish handling any outstanding requests and serve all new incoming ones with the new binary.

Advanced Example

This example demonstrates how you can add custom logging or other behavior to the server

func main() {
    pid := syscall.Getpid()
    service := endless.NewServer("localhost:4242", mux)
    service.ErrorLog = log.New(os.Stderr, fmt.Sprintf("[%d] ", pid), 0)
    service.BeforeStart = func() { log.Printf("[%d] Starting\n", pid) }
    service.BeforeRestart = func() { log.Printf("[%d] Restarting\n", pid) }
    service.BeforeShutdown = func() { log.Printf("[%d] Stopping\n", pid) }
    err := service.ListenAndServe()
    if err != nil {
      log.Printf("[%d] Error: %s\n", pid, err)
    } else {
      log.Printf("[%d] Exited\n", pid)
    }
}