mirror of https://github.com/portainer/portainer
72 lines
1.9 KiB
Go
72 lines
1.9 KiB
Go
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package offlinegate
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import (
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"log"
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"net/http"
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"sync"
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"time"
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httperror "github.com/portainer/libhttp/error"
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)
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// OfflineGate is a entity that works similar to a mutex with a signaling
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// Only the caller that have Locked an gate can unlock it, otherw will be blocked with a call to Lock.
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// Gate provides a passthrough http middleware that will wait for a locked gate to be unlocked.
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// For a safety reasons, middleware will timeout
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type OfflineGate struct {
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lock *sync.Mutex
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signalingCh chan interface{}
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}
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// NewOfflineGate creates a new gate
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func NewOfflineGate() *OfflineGate {
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return &OfflineGate{
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lock: &sync.Mutex{},
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}
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}
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// Lock locks readonly gate and returns a function to unlock
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func (o *OfflineGate) Lock() func() {
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o.lock.Lock()
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o.signalingCh = make(chan interface{})
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return o.unlock
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}
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func (o *OfflineGate) unlock() {
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if o.signalingCh == nil {
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return
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}
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close(o.signalingCh)
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o.signalingCh = nil
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o.lock.Unlock()
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}
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// Watch returns a signaling channel.
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// Unless channel is nil, client needs to watch for a signal on a channel to know when gate is unlocked.
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// Signal channel is disposable: onced signaled, has to be disposed and acquired again.
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func (o *OfflineGate) Watch() chan interface{} {
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return o.signalingCh
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}
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// WaitingMiddleware returns an http handler that waits for the gate to be unlocked before continuing
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func (o *OfflineGate) WaitingMiddleware(timeout time.Duration, next http.Handler) http.Handler {
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return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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signalingCh := o.Watch()
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if signalingCh != nil {
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if r.Method != "GET" && r.Method != "HEAD" && r.Method != "OPTIONS" {
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select {
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case <-signalingCh:
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case <-time.After(timeout):
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log.Println("error: Timeout waiting for the offline gate to signal")
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httperror.WriteError(w, http.StatusRequestTimeout, "Timeout waiting for the offline gate to signal", http.ErrHandlerTimeout)
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}
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}
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}
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next.ServeHTTP(w, r)
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})
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}
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