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| 1 | +package listener |
| 2 | + |
| 3 | +import ( |
| 4 | + "fmt" |
| 5 | + "net" |
| 6 | + "sync/atomic" |
| 7 | + "time" |
| 8 | +) |
| 9 | + |
| 10 | +// ----------------------------------------------------------------------------- |
| 11 | + |
| 12 | +// gracefulListener defines a listener that we can gracefully stop |
| 13 | +type gracefulListener struct { |
| 14 | + // inner listener |
| 15 | + ln net.Listener |
| 16 | + |
| 17 | + // maximum wait time for graceful shutdown |
| 18 | + maxShutdownTime time.Duration |
| 19 | + |
| 20 | + // this channel is closed during graceful shutdown on zero open connections. |
| 21 | + done chan struct{} |
| 22 | + |
| 23 | + // the number of open connections |
| 24 | + activeConnectionsCount uint64 |
| 25 | + |
| 26 | + // becomes non-zero when graceful shutdown starts |
| 27 | + shutdown uint64 |
| 28 | +} |
| 29 | + |
| 30 | +// ----------------------------------------------------------------------------- |
| 31 | + |
| 32 | +// NewGracefulListener wraps the given listener into 'graceful shutdown' listener. |
| 33 | +func NewGracefulListener(ln net.Listener, maxShutdownTime time.Duration) net.Listener { |
| 34 | + return &gracefulListener{ |
| 35 | + ln: ln, |
| 36 | + maxShutdownTime: maxShutdownTime, |
| 37 | + done: make(chan struct{}), |
| 38 | + } |
| 39 | +} |
| 40 | + |
| 41 | +// Accept creates a conn |
| 42 | +func (ln *gracefulListener) Accept() (net.Conn, error) { |
| 43 | + var c net.Conn |
| 44 | + var err error |
| 45 | + |
| 46 | + c, err = ln.ln.Accept() |
| 47 | + if err != nil { |
| 48 | + return nil, err |
| 49 | + } |
| 50 | + |
| 51 | + atomic.AddUint64(&ln.activeConnectionsCount, 1) |
| 52 | + |
| 53 | + return &gracefulConn{ |
| 54 | + Conn: c, |
| 55 | + ln: ln, |
| 56 | + }, nil |
| 57 | +} |
| 58 | + |
| 59 | +// Addr returns the listen address |
| 60 | +func (ln *gracefulListener) Addr() net.Addr { |
| 61 | + return ln.ln.Addr() |
| 62 | +} |
| 63 | + |
| 64 | +// Close closes the inner listener and waits until all the pending |
| 65 | +// open connections are closed before returning. |
| 66 | +func (ln *gracefulListener) Close() error { |
| 67 | + var err error |
| 68 | + |
| 69 | + err = ln.ln.Close() |
| 70 | + if err != nil { |
| 71 | + return err |
| 72 | + } |
| 73 | + |
| 74 | + return ln.waitForZeroConns() |
| 75 | +} |
| 76 | + |
| 77 | +// ----------------------------------------------------------------------------- |
| 78 | +// Private methods |
| 79 | + |
| 80 | +func (ln *gracefulListener) waitForZeroConns() error { |
| 81 | + atomic.AddUint64(&ln.shutdown, 1) |
| 82 | + |
| 83 | + if atomic.LoadUint64(&ln.activeConnectionsCount) == 0 { |
| 84 | + close(ln.done) |
| 85 | + return nil |
| 86 | + } |
| 87 | + |
| 88 | + select { |
| 89 | + case <-ln.done: |
| 90 | + return nil |
| 91 | + case <-time.After(ln.maxShutdownTime): |
| 92 | + return fmt.Errorf("unable to complete graceful shutdown in %s", ln.maxShutdownTime) |
| 93 | + } |
| 94 | +} |
| 95 | + |
| 96 | +func (ln *gracefulListener) connClosed() { |
| 97 | + activeConnectionsCount := atomic.AddUint64(&ln.activeConnectionsCount, ^uint64(0)) |
| 98 | + |
| 99 | + if atomic.LoadUint64(&ln.shutdown) != 0 && activeConnectionsCount == 0 { |
| 100 | + close(ln.done) |
| 101 | + } |
| 102 | +} |
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