func (s *relationsSuite) assertHookRelationDeparted(c *gc.C, numCalls *int32, apiCalls ...apiCall) relation.Relations {
	r := s.assertHookRelationJoined(c, numCalls, apiCalls...)
	s.assertHookRelationChanged(c, r, remotestate.RelationSnapshot{
		Life: params.Alive,
	}, numCalls)
	numCallsBefore := *numCalls

	localState := resolver.LocalState{
		State: operation.State{
			Kind: operation.Continue,
		},
	}
	remoteState := remotestate.Snapshot{
		Relations: map[int]remotestate.RelationSnapshot{
			1: remotestate.RelationSnapshot{
				Life: params.Dying,
				Members: map[string]int64{
					"wordpress": 1,
				},
			},
		},
	}
	relationsResolver := relation.NewRelationsResolver(r)
	op, err := relationsResolver.NextOp(localState, remoteState, &mockOperations{})
	c.Assert(err, jc.ErrorIsNil)
	assertNumCalls(c, numCalls, numCallsBefore+1)
	c.Assert(op.String(), gc.Equals, "run hook relation-departed on unit with relation 1")

	// Commit the operation so we save local state for any next operation.
	_, err = r.PrepareHook(op.(*mockOperation).hookInfo)
	c.Assert(err, jc.ErrorIsNil)
	err = r.CommitHook(op.(*mockOperation).hookInfo)
	c.Assert(err, jc.ErrorIsNil)
	return r
}

func (s *relationsSuite) TestHookRelationBroken(c *gc.C) {
	var numCalls int32
	apiCalls := relationJoinedApiCalls()

	apiCalls = append(apiCalls, getPrincipalApiCalls(3)...)
	r := s.assertHookRelationDeparted(c, &numCalls, apiCalls...)

	localState := resolver.LocalState{
		State: operation.State{
			Kind: operation.Continue,
		},
	}
	remoteState := remotestate.Snapshot{
		Relations: map[int]remotestate.RelationSnapshot{
			1: remotestate.RelationSnapshot{
				Life: params.Dying,
			},
		},
	}
	relationsResolver := relation.NewRelationsResolver(r)
	op, err := relationsResolver.NextOp(localState, remoteState, &mockOperations{})
	c.Assert(err, jc.ErrorIsNil)
	assertNumCalls(c, &numCalls, 11)
	c.Assert(op.String(), gc.Equals, "run hook relation-broken on unit with relation 1")
}

func (s *relationsSuite) TestNextOpNothing(c *gc.C) {
	unitTag := names.NewUnitTag("wordpress/0")
	abort := make(chan struct{})

	var numCalls int32
	unitEntity := params.Entities{Entities: []params.Entity{params.Entity{Tag: "unit-wordpress-0"}}}
	apiCaller := mockAPICaller(c, &numCalls,
		uniterApiCall("Life", unitEntity, params.LifeResults{Results: []params.LifeResult{{Life: params.Alive}}}, nil),
		uniterApiCall("JoinedRelations", unitEntity, params.StringsResults{Results: []params.StringsResult{{Result: []string{}}}}, nil),
		uniterApiCall("GetPrincipal", unitEntity, params.StringBoolResults{Results: []params.StringBoolResult{{Result: "", Ok: false}}}, nil),
	)
	st := uniter.NewState(apiCaller, unitTag)
	r, err := relation.NewRelations(st, unitTag, s.stateDir, s.relationsDir, abort)
	c.Assert(err, jc.ErrorIsNil)
	assertNumCalls(c, &numCalls, 2)

	localState := resolver.LocalState{
		State: operation.State{
			Kind: operation.Continue,
		},
	}
	remoteState := remotestate.Snapshot{}
	relationsResolver := relation.NewRelationsResolver(r)
	_, err = relationsResolver.NextOp(localState, remoteState, &mockOperations{})
	c.Assert(errors.Cause(err), gc.Equals, resolver.ErrNoOperation)
}

func (s *relationsSuite) assertHookRelationChanged(
	c *gc.C, r relation.Relations,
	remoteRelationSnapshot remotestate.RelationSnapshot,
	numCalls *int32,
) {
	numCallsBefore := *numCalls
	localState := resolver.LocalState{
		State: operation.State{
			Kind: operation.Continue,
		},
	}
	remoteState := remotestate.Snapshot{
		Relations: map[int]remotestate.RelationSnapshot{
			1: remoteRelationSnapshot,
		},
	}
	relationsResolver := relation.NewRelationsResolver(r)
	op, err := relationsResolver.NextOp(localState, remoteState, &mockOperations{})
	c.Assert(err, jc.ErrorIsNil)
	assertNumCalls(c, numCalls, numCallsBefore+1)
	c.Assert(op.String(), gc.Equals, "run hook relation-changed on unit with relation 1")

	// Commit the operation so we save local state for any next operation.
	_, err = r.PrepareHook(op.(*mockOperation).hookInfo)
	c.Assert(err, jc.ErrorIsNil)
	err = r.CommitHook(op.(*mockOperation).hookInfo)
	c.Assert(err, jc.ErrorIsNil)
}

func (s *resolverSuite) SetUpTest(c *gc.C) {
	s.stub = testing.Stub{}
	s.charmURL = charm.MustParseURL("cs:precise/mysql-2")
	s.remoteState = remotestate.Snapshot{
		CharmModifiedVersion: s.charmModifiedVersion,
		CharmURL:             s.charmURL,
	}
	s.opFactory = operation.NewFactory(operation.FactoryParams{})

	attachments, err := storage.NewAttachments(&dummyStorageAccessor{}, names.NewUnitTag("u/0"), c.MkDir(), nil)
	c.Assert(err, jc.ErrorIsNil)

	s.clearResolved = func() error {
		return errors.New("unexpected resolved")
	}

	s.reportHookError = func(hook.Info) error {
		return errors.New("unexpected report hook error")
	}

	s.resolverConfig = uniter.ResolverConfig{
		ClearResolved:       func() error { return s.clearResolved() },
		ReportHookError:     func(info hook.Info) error { return s.reportHookError(info) },
		StartRetryHookTimer: func() { s.stub.AddCall("StartRetryHookTimer") },
		StopRetryHookTimer:  func() { s.stub.AddCall("StopRetryHookTimer") },
		ShouldRetryHooks:    true,
		Leadership:          leadership.NewResolver(),
		Actions:             uniteractions.NewResolver(),
		Relations:           relation.NewRelationsResolver(&dummyRelations{}),
		Storage:             storage.NewResolver(attachments),
		Commands:            nopResolver{},
	}

	s.resolver = uniter.NewUniterResolver(s.resolverConfig)
}

func (s *relationsSuite) TestImplicitRelationNoHooks(c *gc.C) {
	unitTag := names.NewUnitTag("wordpress/0")
	abort := make(chan struct{})

	unitEntity := params.Entities{Entities: []params.Entity{params.Entity{Tag: "unit-wordpress-0"}}}
	relationResults := params.RelationResults{
		Results: []params.RelationResult{
			{
				Id:   1,
				Key:  "wordpress:juju-info juju-info:juju-info",
				Life: params.Alive,
				Endpoint: multiwatcher.Endpoint{
					ApplicationName: "wordpress",
					Relation:        multiwatcher.CharmRelation{Name: "juju-info", Role: string(charm.RoleProvider), Interface: "juju-info", Scope: "global"},
				}},
		},
	}
	relationUnits := params.RelationUnits{RelationUnits: []params.RelationUnit{
		{Relation: "relation-wordpress.juju-info#juju-info.juju-info", Unit: "unit-wordpress-0"},
	}}
	apiCalls := []apiCall{
		uniterApiCall("Life", unitEntity, params.LifeResults{Results: []params.LifeResult{{Life: params.Alive}}}, nil),
		uniterApiCall("JoinedRelations", unitEntity, params.StringsResults{Results: []params.StringsResult{{Result: []string{}}}}, nil),
		uniterApiCall("RelationById", params.RelationIds{RelationIds: []int{1}}, relationResults, nil),
		uniterApiCall("Relation", relationUnits, relationResults, nil),
		uniterApiCall("Relation", relationUnits, relationResults, nil),
		uniterApiCall("Watch", unitEntity, params.NotifyWatchResults{Results: []params.NotifyWatchResult{{NotifyWatcherId: "1"}}}, nil),
		uniterApiCall("EnterScope", relationUnits, params.ErrorResults{Results: []params.ErrorResult{{}}}, nil),
		uniterApiCall("GetPrincipal", unitEntity, params.StringBoolResults{Results: []params.StringBoolResult{{Result: "", Ok: false}}}, nil),
	}

	var numCalls int32
	apiCaller := mockAPICaller(c, &numCalls, apiCalls...)
	st := uniter.NewState(apiCaller, unitTag)
	r, err := relation.NewRelations(st, unitTag, s.stateDir, s.relationsDir, abort)
	c.Assert(err, jc.ErrorIsNil)

	localState := resolver.LocalState{
		State: operation.State{
			Kind: operation.Continue,
		},
	}
	remoteState := remotestate.Snapshot{
		Relations: map[int]remotestate.RelationSnapshot{
			1: remotestate.RelationSnapshot{
				Life: params.Alive,
				Members: map[string]int64{
					"wordpress": 1,
				},
			},
		},
	}
	relationsResolver := relation.NewRelationsResolver(r)
	_, err = relationsResolver.NextOp(localState, remoteState, &mockOperations{})
	c.Assert(errors.Cause(err), gc.Equals, resolver.ErrNoOperation)
}

func (s *resolverSuite) SetUpTest(c *gc.C) {
	s.charmURL = charm.MustParseURL("cs:precise/mysql-2")
	s.remoteState = remotestate.Snapshot{
		CharmURL: s.charmURL,
	}
	s.opFactory = operation.NewFactory(operation.FactoryParams{})

	attachments, err := storage.NewAttachments(&dummyStorageAccessor{}, names.NewUnitTag("u/0"), c.MkDir(), nil)
	c.Assert(err, jc.ErrorIsNil)

	s.resolver = uniter.NewUniterResolver(
		func() error { return errors.New("unexpected resolved") },
		func(_ hook.Info) error { return errors.New("unexpected report hook error") },
		func() error { return nil },
		uniteractions.NewResolver(),
		leadership.NewResolver(),
		relation.NewRelationsResolver(&dummyRelations{}),
		storage.NewResolver(attachments),
	)
}

func (s *relationsSuite) assertHookRelationJoined(c *gc.C, numCalls *int32, apiCalls ...apiCall) relation.Relations {
	unitTag := names.NewUnitTag("wordpress/0")
	abort := make(chan struct{})

	apiCaller := mockAPICaller(c, numCalls, apiCalls...)
	st := uniter.NewState(apiCaller, unitTag)
	r, err := relation.NewRelations(st, unitTag, s.stateDir, s.relationsDir, abort)
	c.Assert(err, jc.ErrorIsNil)
	assertNumCalls(c, numCalls, 2)

	localState := resolver.LocalState{
		State: operation.State{
			Kind: operation.Continue,
		},
	}
	remoteState := remotestate.Snapshot{
		Relations: map[int]remotestate.RelationSnapshot{
			1: remotestate.RelationSnapshot{
				Life: params.Alive,
				Members: map[string]int64{
					"wordpress": 1,
				},
			},
		},
	}
	relationsResolver := relation.NewRelationsResolver(r)
	op, err := relationsResolver.NextOp(localState, remoteState, &mockOperations{})
	c.Assert(err, jc.ErrorIsNil)
	assertNumCalls(c, numCalls, 8)
	c.Assert(op.String(), gc.Equals, "run hook relation-joined on unit with relation 1")

	// Commit the operation so we save local state for any next operation.
	_, err = r.PrepareHook(op.(*mockOperation).hookInfo)
	c.Assert(err, jc.ErrorIsNil)
	err = r.CommitHook(op.(*mockOperation).hookInfo)
	c.Assert(err, jc.ErrorIsNil)
	return r
}

//.........这里部分代码省略.........
		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, 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.

//.........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
}