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mox!
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147
mox-/lifecycle.go
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147
mox-/lifecycle.go
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package mox
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import (
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"context"
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"net"
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"runtime/debug"
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"sync"
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"time"
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"github.com/prometheus/client_golang/prometheus"
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"github.com/prometheus/client_golang/prometheus/promauto"
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)
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// Shutdown is closed when a graceful shutdown is initiated. SMTP, IMAP, periodic
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// processes should check this before starting a new operation. If true, the
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// operation should be aborted, and new connections should receive a message that
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// the service is currently not available.
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var Shutdown chan struct{}
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// Context should be used as parent by all operations. It is canceled when mox is
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// shutdown, aborting all pending operations.
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//
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// Operations typically have context timeouts, 30s for single i/o like DNS queries,
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// and 1 minute for operations with more back and forth. These are set through a
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// context.WithTimeout based on this context, so those contexts are still canceled
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// when shutting down.
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//
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// Explicit read/write deadlines on connections, typically 30s.
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//
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// HTTP servers don't get graceful shutdown, their connections are just aborted.
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var Context context.Context
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// Connections holds all active protocol sockets (smtp, imap). They will be given
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// an immediate read/write deadline shortly after initiating mox shutdown, after
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// which the connections get 1 more second for error handling before actual
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// shutdown.
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var Connections = &connections{
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conns: map[net.Conn]connKind{},
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gauges: map[connKind]prometheus.GaugeFunc{},
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active: map[connKind]int64{},
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}
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type connKind struct {
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protocol string
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listener string
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}
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type connections struct {
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sync.Mutex
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conns map[net.Conn]connKind
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dones []chan struct{}
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gauges map[connKind]prometheus.GaugeFunc
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activeMutex sync.Mutex
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active map[connKind]int64
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}
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// Register adds a connection for receiving an immediate i/o deadline on shutdown.
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// When the connection is closed, Remove must be called to cancel the registration.
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func (c *connections) Register(nc net.Conn, protocol, listener string) {
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// This can happen, when a connection was initiated before a shutdown, but it
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// doesn't hurt to log it.
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select {
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case <-Shutdown:
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xlog.Error("new connection added while shutting down")
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debug.PrintStack()
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default:
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}
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ck := connKind{protocol, listener}
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c.activeMutex.Lock()
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c.active[ck]++
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c.activeMutex.Unlock()
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c.Lock()
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defer c.Unlock()
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c.conns[nc] = ck
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if _, ok := c.gauges[ck]; !ok {
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c.gauges[ck] = promauto.NewGaugeFunc(
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prometheus.GaugeOpts{
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Name: "mox_connections_count",
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Help: "Open connections, per protocol/listener.",
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ConstLabels: prometheus.Labels{
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"protocol": protocol,
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"listener": listener,
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},
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},
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func() float64 {
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c.activeMutex.Lock()
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defer c.activeMutex.Unlock()
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return float64(c.active[ck])
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},
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)
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}
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}
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// Unregister removes a connection for shutdown.
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func (c *connections) Unregister(nc net.Conn) {
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c.Lock()
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defer c.Unlock()
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ck := c.conns[nc]
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defer func() {
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c.activeMutex.Lock()
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c.active[ck]--
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c.activeMutex.Unlock()
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}()
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delete(c.conns, nc)
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if len(c.conns) > 0 {
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return
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}
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for _, done := range c.dones {
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done <- struct{}{}
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}
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c.dones = nil
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}
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// Shutdown sets an immediate i/o deadline on all open registered sockets. Called
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// some time after mox shutdown is initiated.
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// The deadline will cause i/o's to be aborted, which should result in the
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// connection being unregistered.
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func (c *connections) Shutdown() {
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now := time.Now()
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c.Lock()
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defer c.Unlock()
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for nc := range c.conns {
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if err := nc.SetDeadline(now); err != nil {
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xlog.Errorx("setting immediate read/write deadline for shutdown", err)
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}
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}
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}
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// Done returns a new channel on which a value is sent when no more sockets are
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// open, which could be immediate.
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func (c *connections) Done() chan struct{} {
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c.Lock()
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defer c.Unlock()
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done := make(chan struct{}, 1)
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if len(c.conns) == 0 {
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done <- struct{}{}
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return done
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}
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c.dones = append(c.dones, done)
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return done
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}
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