github.com/wallyworld/juju@v0.0.0-20161013125918-6cf1bc9d917a/worker/uniter/remotestate/relationunits.go (about)

     1  // Copyright 2015 Canonical Ltd.
     2  // Licensed under the AGPLv3, see LICENCE file for details.
     3  
     4  package remotestate
     5  
     6  import (
     7  	"github.com/juju/errors"
     8  
     9  	"github.com/juju/juju/watcher"
    10  	"github.com/juju/juju/worker"
    11  	"github.com/juju/juju/worker/catacomb"
    12  )
    13  
    14  type relationUnitsWatcher struct {
    15  	catacomb   catacomb.Catacomb
    16  	relationId int
    17  	changes    watcher.RelationUnitsChannel
    18  	out        chan<- relationUnitsChange
    19  }
    20  
    21  type relationUnitsChange struct {
    22  	relationId int
    23  	watcher.RelationUnitsChange
    24  }
    25  
    26  // newRelationUnitsWatcher creates a new worker that takes values from the
    27  // supplied watcher's Changes chan, annotates them with the supplied relation
    28  // id, and delivers then on the supplied out chan.
    29  //
    30  // The caller releases responsibility for stopping the supplied watcher and
    31  // waiting for errors, *whether or not this method succeeds*.
    32  func newRelationUnitsWatcher(
    33  	relationId int,
    34  	watcher watcher.RelationUnitsWatcher,
    35  	out chan<- relationUnitsChange,
    36  ) (*relationUnitsWatcher, error) {
    37  	ruw := &relationUnitsWatcher{
    38  		relationId: relationId,
    39  		changes:    watcher.Changes(),
    40  		out:        out,
    41  	}
    42  	err := catacomb.Invoke(catacomb.Plan{
    43  		Site: &ruw.catacomb,
    44  		Work: ruw.loop,
    45  		Init: []worker.Worker{watcher},
    46  	})
    47  	if err != nil {
    48  		return nil, errors.Trace(err)
    49  	}
    50  	return ruw, nil
    51  }
    52  
    53  // Kill is part of the worker.Worker interface.
    54  func (w *relationUnitsWatcher) Kill() {
    55  	w.catacomb.Kill(nil)
    56  }
    57  
    58  // Wait is part of the worker.Worker interface.
    59  func (w *relationUnitsWatcher) Wait() error {
    60  	return w.catacomb.Wait()
    61  }
    62  
    63  func (w *relationUnitsWatcher) loop() error {
    64  	for {
    65  		select {
    66  		case <-w.catacomb.Dying():
    67  			return w.catacomb.ErrDying()
    68  		case change, ok := <-w.changes:
    69  			if !ok {
    70  				return errors.New("watcher closed channel")
    71  			}
    72  			select {
    73  			case <-w.catacomb.Dying():
    74  				return w.catacomb.ErrDying()
    75  			case w.out <- relationUnitsChange{w.relationId, change}:
    76  			}
    77  		}
    78  	}
    79  }