github.com/niedbalski/juju@v0.0.0-20190215020005-8ff100488e47/apiserver/common/modelmachineswatcher.go (about)

     1  // Copyright 2013 Canonical Ltd.
     2  // Licensed under the AGPLv3, see LICENCE file for details.
     3  
     4  package common
     5  
     6  import (
     7  	"fmt"
     8  
     9  	"github.com/juju/juju/apiserver/facade"
    10  	"github.com/juju/juju/apiserver/params"
    11  	"github.com/juju/juju/state"
    12  	"github.com/juju/juju/state/watcher"
    13  )
    14  
    15  // ModelMachinesWatcher implements a common WatchModelMachines
    16  // method for use by various facades.
    17  type ModelMachinesWatcher struct {
    18  	st         state.ModelMachinesWatcher
    19  	resources  facade.Resources
    20  	authorizer facade.Authorizer
    21  }
    22  
    23  // NewModelMachinesWatcher returns a new ModelMachinesWatcher. The
    24  // GetAuthFunc will be used on each invocation of WatchUnits to
    25  // determine current permissions.
    26  func NewModelMachinesWatcher(st state.ModelMachinesWatcher, resources facade.Resources, authorizer facade.Authorizer) *ModelMachinesWatcher {
    27  	return &ModelMachinesWatcher{
    28  		st:         st,
    29  		resources:  resources,
    30  		authorizer: authorizer,
    31  	}
    32  }
    33  
    34  // WatchModelMachines returns a StringsWatcher that notifies of
    35  // changes to the life cycles of the top level machines in the current
    36  // model.
    37  func (e *ModelMachinesWatcher) WatchModelMachines() (params.StringsWatchResult, error) {
    38  	result := params.StringsWatchResult{}
    39  	if !e.authorizer.AuthController() {
    40  		return result, ErrPerm
    41  	}
    42  	watch := e.st.WatchModelMachines()
    43  	// Consume the initial event and forward it to the result.
    44  	if changes, ok := <-watch.Changes(); ok {
    45  		result.StringsWatcherId = e.resources.Register(watch)
    46  		result.Changes = changes
    47  	} else {
    48  		err := watcher.EnsureErr(watch)
    49  		return result, fmt.Errorf("cannot obtain initial model machines: %v", err)
    50  	}
    51  	return result, nil
    52  }