63 lines
1.5 KiB
Markdown
63 lines
1.5 KiB
Markdown
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# Graceful process restarts in Go
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[](https://godoc.org/github.com/cloudflare/tableflip)
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It is sometimes useful to update the running code and / or configuration of a
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network service, without disrupting existing connections. Usually, this is
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achieved by starting a new process, somehow transferring clients to it and
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then exiting the old process.
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There are [many ways to implement graceful upgrades](https://blog.cloudflare.com/graceful-upgrades-in-go/).
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They vary wildly in the trade-offs they make, and how much control they afford the user. This library
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has the following goals:
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* No old code keeps running after a successful upgrade
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* The new process has a grace period for performing initialisation
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* Crashing during initialisation is OK
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* Only a single upgrade is ever run in parallel
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`tableflip` does not work on Windows.
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It's easy to get started:
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```Go
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upg, err := tableflip.New(tableflip.Options{})
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if err != nil {
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panic(err)
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}
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defer upg.Stop()
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go func() {
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sig := make(chan os.Signal, 1)
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signal.Notify(sig, syscall.SIGHUP)
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for range sig {
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err := upg.Upgrade()
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if err != nil {
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log.Println("Upgrade failed:", err)
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continue
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}
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log.Println("Upgrade succeeded")
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}
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}()
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ln, err := upg.Fds.Listen("tcp", "localhost:8080")
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if err != nil {
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log.Fatalln("Can't listen:", err)
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}
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var server http.Server
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go server.Serve(ln)
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if err := upg.Ready(); err != nil {
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panic(err)
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}
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<-upg.Exit()
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time.AfterFunc(30*time.Second, func() {
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os.Exit(1)
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})
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_ = server.Shutdown(context.Background())
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```
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