github.com/makyo/juju@v0.0.0-20160425123129-2608902037e9/apiserver/migrationflag/facade.go (about)

     1  // Copyright 2016 Canonical Ltd.
     2  // Licensed under the LGPLv3, see LICENCE file for details.
     3  
     4  package migrationflag
     5  
     6  import (
     7  	"github.com/juju/errors"
     8  	"github.com/juju/names"
     9  
    10  	"github.com/juju/juju/apiserver/common"
    11  	"github.com/juju/juju/apiserver/params"
    12  	"github.com/juju/juju/core/migration"
    13  	"github.com/juju/juju/state"
    14  	"github.com/juju/juju/state/watcher"
    15  )
    16  
    17  // Backend exposes information about any current model migrations.
    18  type Backend interface {
    19  	ModelUUID() string
    20  	MigrationPhase() (migration.Phase, error)
    21  	WatchMigrationPhase() (state.NotifyWatcher, error)
    22  }
    23  
    24  // Facade lets clients watch and get models' migration phases.
    25  type Facade struct {
    26  	backend   Backend
    27  	resources *common.Resources
    28  }
    29  
    30  // New creates a Facade backed by backend and resources. If auth
    31  // doesn't identity the client as a machine agent or a unit agent,
    32  // it will return common.ErrPerm.
    33  func New(backend Backend, resources *common.Resources, auth common.Authorizer) (*Facade, error) {
    34  	if !auth.AuthMachineAgent() && !auth.AuthUnitAgent() {
    35  		return nil, common.ErrPerm
    36  	}
    37  	return &Facade{
    38  		backend:   backend,
    39  		resources: resources,
    40  	}, nil
    41  }
    42  
    43  // auth is very simplistic: it only accepts the model tag reported by
    44  // the backend.
    45  func (facade *Facade) auth(tagString string) error {
    46  	tag, err := names.ParseModelTag(tagString)
    47  	if err != nil {
    48  		return errors.Trace(err)
    49  	}
    50  	if tag.Id() != facade.backend.ModelUUID() {
    51  		return common.ErrPerm
    52  	}
    53  	return nil
    54  }
    55  
    56  // Phase returns the current migration phase or an error for every
    57  // supplied entity.
    58  func (facade *Facade) Phase(entities params.Entities) params.PhaseResults {
    59  	count := len(entities.Entities)
    60  	results := params.PhaseResults{
    61  		Results: make([]params.PhaseResult, count),
    62  	}
    63  	for i, entity := range entities.Entities {
    64  		phase, err := facade.onePhase(entity.Tag)
    65  		results.Results[i].Phase = phase
    66  		results.Results[i].Error = common.ServerError(err)
    67  	}
    68  	return results
    69  }
    70  
    71  // onePhase does auth and lookup for a single entity.
    72  func (facade *Facade) onePhase(tagString string) (string, error) {
    73  	if err := facade.auth(tagString); err != nil {
    74  		return "", errors.Trace(err)
    75  	}
    76  	phase, err := facade.backend.MigrationPhase()
    77  	if err != nil {
    78  		return "", errors.Trace(err)
    79  	}
    80  	return phase.String(), nil
    81  }
    82  
    83  // Watch returns an id for use with the NotifyWatcher facade, or an
    84  // error, for every supplied entity.
    85  func (facade *Facade) Watch(entities params.Entities) params.NotifyWatchResults {
    86  	count := len(entities.Entities)
    87  	results := params.NotifyWatchResults{
    88  		Results: make([]params.NotifyWatchResult, count),
    89  	}
    90  	for i, entity := range entities.Entities {
    91  		id, err := facade.oneWatch(entity.Tag)
    92  		results.Results[i].NotifyWatcherId = id
    93  		results.Results[i].Error = common.ServerError(err)
    94  	}
    95  	return results
    96  }
    97  
    98  // oneWatch does auth, and watcher creation/registration, for a single
    99  // entity.
   100  func (facade *Facade) oneWatch(tagString string) (string, error) {
   101  	if err := facade.auth(tagString); err != nil {
   102  		return "", errors.Trace(err)
   103  	}
   104  	watch, err := facade.backend.WatchMigrationPhase()
   105  	if err != nil {
   106  		return "", errors.Trace(err)
   107  	}
   108  	if _, ok := <-watch.Changes(); ok {
   109  		return facade.resources.Register(watch), nil
   110  	}
   111  	return "", watcher.EnsureErr(watch)
   112  }