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| 1 | +package appext |
| 2 | + |
| 3 | +import ( |
| 4 | + "context" |
| 5 | + "log" |
| 6 | + "os" |
| 7 | + "os/signal" |
| 8 | + "syscall" |
| 9 | + "time" |
| 10 | +) |
| 11 | + |
| 12 | +type contextBuilder struct { |
| 13 | + signals []os.Signal |
| 14 | + timeout time.Duration |
| 15 | + exitFn func(int) |
| 16 | + forceExit bool |
| 17 | +} |
| 18 | + |
| 19 | +// Context returns a new context builder, with sane defaults, that can be overridden. Calling `Build()` finalizes |
| 20 | +// the new desired context and returns the configured `context.Context`. |
| 21 | +func Context() *contextBuilder { |
| 22 | + return &contextBuilder{ |
| 23 | + signals: []os.Signal{ |
| 24 | + os.Interrupt, |
| 25 | + syscall.SIGTERM, |
| 26 | + syscall.SIGQUIT, |
| 27 | + }, |
| 28 | + timeout: 30 * time.Second, |
| 29 | + forceExit: true, |
| 30 | + exitFn: os.Exit, |
| 31 | + } |
| 32 | +} |
| 33 | + |
| 34 | +// Signals sets the signals to listen for. Defaults to `os.Interrupt, syscall.SIGTERM, syscall.SIGQUIT`. |
| 35 | +func (c *contextBuilder) Signals(signals ...os.Signal) *contextBuilder { |
| 36 | + c.signals = signals |
| 37 | + return c |
| 38 | +} |
| 39 | + |
| 40 | +// Timeout sets the timeout for graceful shutdown before forcing the issue exiting with exit code 1. |
| 41 | +// Defaults to 30 seconds. |
| 42 | +// |
| 43 | +// A timeout of <= 0, not recommended, disables the timeout and will wait forever for a seconds signal or application |
| 44 | +// shuts down. |
| 45 | +func (c *contextBuilder) Timeout(timeout time.Duration) *contextBuilder { |
| 46 | + c.timeout = timeout |
| 47 | + return c |
| 48 | +} |
| 49 | + |
| 50 | +// ForceExit sets whether to force terminate ungracefully upon receipt of a second signal. Defaults to true. |
| 51 | +func (c *contextBuilder) ForceExit(forceExit bool) *contextBuilder { |
| 52 | + c.forceExit = forceExit |
| 53 | + return c |
| 54 | +} |
| 55 | + |
| 56 | +// ExitFn sets the exit function to use. Defaults to `os.Exit`. |
| 57 | +// |
| 58 | +// This is used in the unit tests but can be used to intercept the exit call and do something else as needed also. |
| 59 | +func (c *contextBuilder) ExitFn(exitFn func(int)) *contextBuilder { |
| 60 | + c.exitFn = exitFn |
| 61 | + return c |
| 62 | +} |
| 63 | + |
| 64 | +// Build finalizes the context builder and returns the configured `context.Context`. |
| 65 | +// |
| 66 | +// This will spawn another goroutine listening for the configured signals and will cancel the context when received with |
| 67 | +// the configured settings. |
| 68 | +func (c *contextBuilder) Build() context.Context { |
| 69 | + var sig = make(chan os.Signal, 1) |
| 70 | + signal.Notify(sig, c.signals...) |
| 71 | + |
| 72 | + ctx, cancel := context.WithCancel(context.Background()) |
| 73 | + |
| 74 | + go listen(sig, cancel, c.exitFn, c.timeout, c.forceExit) |
| 75 | + |
| 76 | + return ctx |
| 77 | +} |
| 78 | + |
| 79 | +func listen(sig <-chan os.Signal, cancel context.CancelFunc, exitFn func(int), timeout time.Duration, forceExit bool) { |
| 80 | + s := <-sig |
| 81 | + cancel() |
| 82 | + log.Printf("received shutdown signal %q\n", s) |
| 83 | + |
| 84 | + if timeout > 0 { |
| 85 | + select { |
| 86 | + case s := <-sig: |
| 87 | + if forceExit { |
| 88 | + log.Printf("received second shutdown signal %q, forcing exit\n", s) |
| 89 | + exitFn(1) |
| 90 | + } |
| 91 | + case <-time.After(timeout): |
| 92 | + log.Printf("timeout of %s reached, forcing exit\n", timeout) |
| 93 | + exitFn(1) |
| 94 | + } |
| 95 | + } else { |
| 96 | + s = <-sig |
| 97 | + if forceExit { |
| 98 | + log.Printf("received second shutdown signal %q, forcing exit\n", s) |
| 99 | + exitFn(1) |
| 100 | + } |
| 101 | + } |
| 102 | +} |
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