func (s *resolverSuite) TestRunHookStopRetryTimer(c *gc.C) {
	s.reportHookError = func(hook.Info) error { return nil }
	localState := resolver.LocalState{
		CharmModifiedVersion: s.charmModifiedVersion,
		CharmURL:             s.charmURL,
		State: operation.State{
			Kind:      operation.RunHook,
			Step:      operation.Pending,
			Installed: true,
			Started:   true,
			Hook: &hook.Info{
				Kind: hooks.ConfigChanged,
			},
		},
	}

	_, err := s.resolver.NextOp(localState, s.remoteState, s.opFactory)
	c.Assert(err, gc.Equals, resolver.ErrNoOperation)
	s.stub.CheckCallNames(c, "StartRetryHookTimer")

	localState.Kind = operation.Continue
	_, err = s.resolver.NextOp(localState, s.remoteState, s.opFactory)
	c.Assert(err, gc.Equals, resolver.ErrNoOperation)
	s.stub.CheckCallNames(c, "StartRetryHookTimer", "StopRetryHookTimer")
}

func (s *resolverSuite) TestHookErrorStartRetryTimerAgain(c *gc.C) {
	s.reportHookError = func(hook.Info) error { return nil }
	localState := resolver.LocalState{
		CharmModifiedVersion: s.charmModifiedVersion,
		CharmURL:             s.charmURL,
		State: operation.State{
			Kind:      operation.RunHook,
			Step:      operation.Pending,
			Installed: true,
			Started:   true,
			Hook: &hook.Info{
				Kind: hooks.ConfigChanged,
			},
		},
	}

	_, err := s.resolver.NextOp(localState, s.remoteState, s.opFactory)
	c.Assert(err, gc.Equals, resolver.ErrNoOperation)
	s.stub.CheckCallNames(c, "StartRetryHookTimer")

	s.remoteState.RetryHookVersion = 1
	op, err := s.resolver.NextOp(localState, s.remoteState, s.opFactory)
	c.Assert(err, jc.ErrorIsNil)
	c.Assert(op.String(), gc.Equals, "run config-changed hook")
	s.stub.CheckCallNames(c, "StartRetryHookTimer") // no change
	localState.RetryHookVersion = 1

	_, err = s.resolver.NextOp(localState, s.remoteState, s.opFactory)
	c.Assert(err, gc.Equals, resolver.ErrNoOperation)
	s.stub.CheckCallNames(c, "StartRetryHookTimer", "StartRetryHookTimer")
}

//.........这里部分代码省略.........
			// the "Continue" state, which indicates that
			// there is nothing to do and we're not in an
			// error state.
			return nil
		}
		return setAgentStatus(u, status.StatusIdle, "", nil)
	}

	clearResolved := func() error {
		if err := u.unit.ClearResolved(); err != nil {
			return errors.Trace(err)
		}
		watcher.ClearResolvedMode()
		return nil
	}

	for {
		if err = restartWatcher(); err != nil {
			err = errors.Annotate(err, "(re)starting watcher")
			break
		}

		uniterResolver := NewUniterResolver(ResolverConfig{
			ClearResolved:       clearResolved,
			ReportHookError:     u.reportHookError,
			FixDeployer:         u.deployer.Fix,
			ShouldRetryHooks:    u.hookRetryStrategy.ShouldRetry,
			StartRetryHookTimer: retryHookTimer.Start,
			StopRetryHookTimer:  retryHookTimer.Reset,
			Actions:             actions.NewResolver(),
			Leadership:          uniterleadership.NewResolver(),
			Relations:           relation.NewRelationsResolver(u.relations),
			Storage:             storage.NewResolver(u.storage),
			Commands: runcommands.NewCommandsResolver(
				u.commands, watcher.CommandCompleted,
			),
		})

		// We should not do anything until there has been a change
		// to the remote state. The watcher will trigger at least
		// once initially.
		select {
		case <-u.catacomb.Dying():
			return u.catacomb.ErrDying()
		case <-watcher.RemoteStateChanged():
		}

		localState := resolver.LocalState{
			CharmURL:             charmURL,
			CharmModifiedVersion: charmModifiedVersion,
		}
		for err == nil {
			err = resolver.Loop(resolver.LoopConfig{
				Resolver:      uniterResolver,
				Watcher:       watcher,
				Executor:      u.operationExecutor,
				Factory:       u.operationFactory,
				Abort:         u.catacomb.Dying(),
				OnIdle:        onIdle,
				CharmDirGuard: u.charmDirGuard,
			}, &localState)
			switch cause := errors.Cause(err); cause {
			case nil:
				// Loop back around.
			case resolver.ErrLoopAborted:
				err = u.catacomb.ErrDying()
			case operation.ErrNeedsReboot:
				err = worker.ErrRebootMachine
			case operation.ErrHookFailed:
				// Loop back around. The resolver can tell that it is in
				// an error state by inspecting the operation state.
				err = nil
			case resolver.ErrTerminate:
				err = u.terminate()
			case resolver.ErrRestart:
				// make sure we update the two values used above in
				// creating LocalState.
				charmURL = localState.CharmURL
				charmModifiedVersion = localState.CharmModifiedVersion
				// leave err assigned, causing loop to break
			default:
				// We need to set conflicted from here, because error
				// handling is outside of the resolver's control.
				if operation.IsDeployConflictError(cause) {
					localState.Conflicted = true
					err = setAgentStatus(u, status.StatusError, "upgrade failed", nil)
				} else {
					reportAgentError(u, "resolver loop error", err)
				}
			}
		}

		if errors.Cause(err) != resolver.ErrRestart {
			break
		}
	}

	logger.Infof("unit %q shutting down: %s", u.unit, err)
	return err
}

//.........这里部分代码省略.........
		defer watcherMu.Unlock()

		if watcher != nil {
			return watcher.Stop()
		}
		return nil
	})

	onIdle := func() error {
		opState := u.operationExecutor.State()
		if opState.Kind != operation.Continue {
			// We should only set idle status if we're in
			// the "Continue" state, which indicates that
			// there is nothing to do and we're not in an
			// error state.
			return nil
		}
		return setAgentStatus(u, params.StatusIdle, "", nil)
	}

	clearResolved := func() error {
		if err := u.unit.ClearResolved(); err != nil {
			return errors.Trace(err)
		}
		watcher.ClearResolvedMode()
		return nil
	}

	for {
		if err = restartWatcher(); err != nil {
			err = errors.Annotate(err, "(re)starting watcher")
			break
		}

		uniterResolver := &uniterResolver{
			clearResolved:      clearResolved,
			reportHookError:    u.reportHookError,
			fixDeployer:        u.deployer.Fix,
			actionsResolver:    actions.NewResolver(),
			leadershipResolver: uniterleadership.NewResolver(),
			relationsResolver:  relation.NewRelationsResolver(u.relations),
			storageResolver:    storage.NewResolver(u.storage),
		}

		// We should not do anything until there has been a change
		// to the remote state. The watcher will trigger at least
		// once initially.
		select {
		case <-u.tomb.Dying():
			return tomb.ErrDying
		case <-watcher.RemoteStateChanged():
		}

		localState := resolver.LocalState{CharmURL: charmURL}
		for err == nil {
			err = resolver.Loop(resolver.LoopConfig{
				Resolver:       uniterResolver,
				Watcher:        watcher,
				Executor:       u.operationExecutor,
				Factory:        u.operationFactory,
				Dying:          u.tomb.Dying(),
				OnIdle:         onIdle,
				CharmDirLocker: u.charmDirLocker,
			}, &localState)
			switch cause := errors.Cause(err); cause {
			case nil:
				// Loop back around.
			case tomb.ErrDying:
				err = tomb.ErrDying
			case operation.ErrNeedsReboot:
				err = worker.ErrRebootMachine
			case operation.ErrHookFailed:
				// Loop back around. The resolver can tell that it is in
				// an error state by inspecting the operation state.
				err = nil
			case resolver.ErrTerminate:
				err = u.terminate()
			case resolver.ErrRestart:
				charmURL = localState.CharmURL
				// leave err assigned, causing loop to break
			default:
				// We need to set conflicted from here, because error
				// handling is outside of the resolver's control.
				if operation.IsDeployConflictError(cause) {
					localState.Conflicted = true
					err = setAgentStatus(u, params.StatusError, "upgrade failed", nil)
				} else {
					reportAgentError(u, "resolver loop error", err)
				}
			}
		}

		if errors.Cause(err) != resolver.ErrRestart {
			break
		}
	}

	logger.Infof("unit %q shutting down: %s", u.unit, err)
	return err
}