circuit_state.go

package healthsrv

import (
	"fmt"

	"github.com/deis/builder/pkg/sshd"
)

// circuitState determines whether circ.State() == sshd.ClosedState, and sends the results back on
//  the various given channels. This func is intended to be run in a goroutine and communicates
// via the channels it's passed.
//
// If the circuit is closed, it passes an empty struct back on succCh. On failure, it sends an
// error back on errCh. At most one of {succCh, errCh} will be sent on. If stopCh is closed, no
// pending or future sends will occur.
func circuitState(circ *sshd.Circuit, succCh chan<- struct{}, errCh chan<- error, stopCh <-chan struct{}) {
	// There's a race between the boolean eval and the HTTP error returned
	// (the circuit could close between the two). This function should be polled to avoid that
	// problem. If it's being used in a k8s probe, then you're fine because k8s will repeat the
	// health probe and effectively re-evaluate the boolean.
	if circ.State() != sshd.ClosedState {
		select {
		case errCh <- fmt.Errorf("SSH Server is not yet started"):
		case <-stopCh:
		}
		return
	}
	select {
	case succCh <- struct{}{}:
	case <-stopCh:
	}
}