mirror of https://github.com/docker/docs.git
77 lines
2.4 KiB
Go
77 lines
2.4 KiB
Go
/*
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Package listenbuffer uses the kernel's listening backlog functionality to queue
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connections, allowing applications to start listening immediately and handle
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connections later. This is signaled by closing the activation channel passed to
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the constructor.
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The maximum amount of queued connections depends on the configuration of your
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kernel (typically called SOMAXXCON) and cannot be configured in Go with the
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net package. See `src/net/sock_platform.go` in the Go tree or consult your
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kernel's manual.
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activator := make(chan struct{})
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buffer, err := NewListenBuffer("tcp", "localhost:4000", activator)
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if err != nil {
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panic(err)
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}
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// will block until activator has been closed or is sent an event
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client, err := buffer.Accept()
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Somewhere else in your application once it's been booted:
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close(activator)
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`buffer.Accept()` will return the first client in the kernel listening queue, or
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continue to block until a client connects or an error occurs.
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*/
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package listenbuffer
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import "net"
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// NewListenBuffer returns a net.Listener listening on addr with the protocol
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// passed. The channel passed is used to activate the listenbuffer when the
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// caller is ready to accept connections.
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func NewListenBuffer(proto, addr string, activate <-chan struct{}) (net.Listener, error) {
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wrapped, err := net.Listen(proto, addr)
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if err != nil {
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return nil, err
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}
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return &defaultListener{
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wrapped: wrapped,
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activate: activate,
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}, nil
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}
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// defaultListener is the buffered wrapper around the net.Listener
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type defaultListener struct {
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wrapped net.Listener // The net.Listener wrapped by listenbuffer
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ready bool // Whether the listenbuffer has been activated
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activate <-chan struct{} // Channel to control activation of the listenbuffer
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}
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// Close closes the wrapped socket.
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func (l *defaultListener) Close() error {
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return l.wrapped.Close()
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}
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// Addr returns the listening address of the wrapped socket.
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func (l *defaultListener) Addr() net.Addr {
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return l.wrapped.Addr()
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}
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// Accept returns a client connection on the wrapped socket if the listen buffer
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// has been activated. To active the listenbuffer the activation channel passed
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// to NewListenBuffer must have been closed or sent an event.
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func (l *defaultListener) Accept() (net.Conn, error) {
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// if the listen has been told it is ready then we can go ahead and
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// start returning connections
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if l.ready {
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return l.wrapped.Accept()
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}
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<-l.activate
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l.ready = true
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return l.Accept()
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}
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