github.com/rogpeppe/juju@v0.0.0-20140613142852-6337964b789e/state/api/deployer/machine.go (about)

     1  // Copyright 2012, 2013 Canonical Ltd.
     2  // Licensed under the AGPLv3, see LICENCE file for details.
     3  
     4  package deployer
     5  
     6  import (
     7  	"fmt"
     8  
     9  	"github.com/juju/juju/state/api/params"
    10  	"github.com/juju/juju/state/api/watcher"
    11  )
    12  
    13  // Machine represents a juju machine as seen by the deployer worker.
    14  type Machine struct {
    15  	tag string
    16  	st  *State
    17  }
    18  
    19  // WatchUnits starts a StringsWatcher to watch all units deployed to
    20  // the machine, in order to track which ones should be deployed or
    21  // recalled.
    22  func (m *Machine) WatchUnits() (watcher.StringsWatcher, error) {
    23  	var results params.StringsWatchResults
    24  	args := params.Entities{
    25  		Entities: []params.Entity{{Tag: m.tag}},
    26  	}
    27  	err := m.st.call("WatchUnits", args, &results)
    28  	if err != nil {
    29  		return nil, err
    30  	}
    31  	if len(results.Results) != 1 {
    32  		return nil, fmt.Errorf("expected 1 result, got %d", len(results.Results))
    33  	}
    34  	result := results.Results[0]
    35  	if result.Error != nil {
    36  		return nil, result.Error
    37  	}
    38  	w := watcher.NewStringsWatcher(m.st.caller, result)
    39  	return w, nil
    40  }