Method checkDrained

nats.go:5208–5261

checkDrained will watch for a subscription to be fully drained and then remove it.

(sub *Subscription)

// checkDrained will watch for a subscription to be fully drained
// and then remove it.
func (nc *Conn) checkDrained(sub *Subscription) {
	if nc == nil || sub == nil {
		return
	}
	defer func() {
		sub.mu.Lock()
		defer sub.mu.Unlock()
		sub.draining = false
	}()

	// This allows us to know that whatever we have in the client pending
	// is correct and the server will not send additional information.
	nc.Flush()

	sub.mu.Lock()
	// For JS subscriptions, check if we are going to delete the
	// JS consumer when drain completes.
	dc := sub.jsi != nil && sub.jsi.dc
	sub.mu.Unlock()

	// Once we are here we just wait for Pending to reach 0 or
	// any other state to exit this go routine.
	for {
		// check connection is still valid.
		if nc.IsClosed() {
			return
		}

		// Check subscription state
		sub.mu.Lock()
		conn := sub.conn
		closed := sub.closed
		pMsgs := sub.pMsgs
		sub.mu.Unlock()

		if conn == nil || closed || pMsgs == 0 {
			nc.mu.Lock()
			nc.removeSub(sub)
			nc.mu.Unlock()
			if dc {
				if err := sub.deleteConsumer(); err != nil {
					nc.mu.Lock()
					if errCB := nc.Opts.AsyncErrorCB; errCB != nil {
						nc.ach.push(func() { errCB(nc, sub, err) })
					}
					nc.mu.Unlock()
				}
			}
			return
		}

		time.Sleep(100 * time.Millisecond)
	}
}

// AutoUnsubscribe will issue an automatic Unsubscribe that is
// processed by the server when max messages have been received.