Пример #1
0
// breakpointListLoop repeatedly calls the Debuglet Controller's List RPC, and
// passes the results to the BreakpointStore so it can set and unset breakpoints
// in the program.
//
// After the first List call finishes, ch is closed.
func breakpointListLoop(c *debuglet.Controller, bs *breakpoints.BreakpointStore, first chan bool) {
	const (
		avgTimeBetweenCalls = time.Second
		errorDelay          = 5 * time.Second
	)

	// randomDuration returns a random duration with expected value avg.
	randomDuration := func(avg time.Duration) time.Duration {
		return time.Duration(rand.Int63n(int64(2*avg + 1)))
	}

	var consecutiveFailures uint

	for {
		callStart := time.Now()
		resp, err := c.List()
		if err != nil && err != debuglet.ErrListUnchanged {
			log.Printf("Debuglet controller server error: %v", err)
		}
		if err == nil {
			bs.ProcessBreakpointList(resp.Breakpoints)
		}

		if first != nil {
			// We've finished one call to List and set any breakpoints we received.
			close(first)
			first = nil
		}

		// Asynchronously send updates for any breakpoints that caused an error when
		// the BreakpointStore tried to process them.  We don't wait for the update
		// to finish before the program can exit, as we do for normal updates.
		errorBps := bs.ErrorBreakpoints()
		for _, bp := range errorBps {
			go func(bp *cd.Breakpoint) {
				if err := c.Update(bp.Id, bp); err != nil {
					log.Printf("Failed to send breakpoint update for %s: %s", bp.Id, err)
				}
			}(bp)
		}

		// Make the next call not too soon after the one we just did.
		delay := randomDuration(avgTimeBetweenCalls)

		// If the call returned an error other than ErrListUnchanged, wait longer.
		if err != nil && err != debuglet.ErrListUnchanged {
			// Wait twice as long after each consecutive failure, to a maximum of 16x.
			delay += randomDuration(errorDelay * (1 << consecutiveFailures))
			if consecutiveFailures < 4 {
				consecutiveFailures++
			}
		} else {
			consecutiveFailures = 0
		}

		// Sleep until we reach time callStart+delay.  If we've already passed that
		// time, time.Sleep will return immediately -- this should be the common
		// case, since the server will delay responding to List for a while when
		// there are no changes to report.
		time.Sleep(callStart.Add(delay).Sub(time.Now()))
	}
}