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package caddy2
import (
"fmt"
"net"
"sync"
"sync/atomic"
)
// Listen returns a listener suitable for use in a Caddy module.
func Listen(network, addr string) (net.Listener, error) {
lnKey := network + "/" + addr
listenersMu.Lock()
defer listenersMu.Unlock()
// if listener already exists, return it
if ln, ok := listeners[lnKey]; ok {
return &fakeCloseListener{Listener: ln}, nil
}
// or, create new one and save it
ln, err := net.Listen(network, addr)
if err != nil {
return nil, err
}
listeners[lnKey] = ln
return &fakeCloseListener{Listener: ln}, nil
}
// fakeCloseListener's Close() method is a no-op. This allows
// stopping servers that are using the listener without giving
// up the socket; thus, servers become hot-swappable while the
// listener remains running. Listeners should be re-wrapped in
// a new fakeCloseListener each time the listener is reused.
type fakeCloseListener struct {
closed int32
net.Listener
}
// Accept accepts connections until Close() is called.
func (fcl *fakeCloseListener) Accept() (net.Conn, error) {
if atomic.LoadInt32(&fcl.closed) == 1 {
return nil, ErrSwappingServers
}
return fcl.Listener.Accept()
}
// Close stops accepting new connections, but does not
// actually close the underlying listener.
func (fcl *fakeCloseListener) Close() error {
atomic.StoreInt32(&fcl.closed, 1)
return nil
}
// CloseUnderlying actually closes the underlying listener.
func (fcl *fakeCloseListener) CloseUnderlying() error {
return fcl.Listener.Close()
}
// ErrSwappingServers is returned by fakeCloseListener when
// Close() is called, indicating that it is pretending to
// be closed so that the server using it can terminate.
var ErrSwappingServers = fmt.Errorf("listener 'closed' 😉")
var (
listeners = make(map[string]net.Listener)
listenersMu sync.Mutex
)
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