github.com/axw/juju@v0.0.0-20161005053422-4bd6544d08d4/worker/singular/manifold.go (about)

     1  // Copyright 2015-2016 Canonical Ltd.
     2  // Licensed under the AGPLv3, see LICENCE file for details.
     3  
     4  package singular
     5  
     6  import (
     7  	"time"
     8  
     9  	"github.com/juju/errors"
    10  	"github.com/juju/juju/agent"
    11  	"github.com/juju/juju/api/base"
    12  	"github.com/juju/juju/cmd/jujud/agent/engine"
    13  	"github.com/juju/juju/worker"
    14  	"github.com/juju/juju/worker/dependency"
    15  	"github.com/juju/utils/clock"
    16  	"gopkg.in/juju/names.v2"
    17  )
    18  
    19  // ManifoldConfig holds the information necessary to run a FlagWorker in
    20  // a dependency.Engine.
    21  type ManifoldConfig struct {
    22  	ClockName     string
    23  	APICallerName string
    24  	AgentName     string
    25  	Duration      time.Duration
    26  
    27  	NewFacade func(base.APICaller, names.MachineTag) (Facade, error)
    28  	NewWorker func(FlagConfig) (worker.Worker, error)
    29  }
    30  
    31  // start is a method on ManifoldConfig because it's more readable than a closure.
    32  func (config ManifoldConfig) start(context dependency.Context) (worker.Worker, error) {
    33  	var clock clock.Clock
    34  	if err := context.Get(config.ClockName, &clock); err != nil {
    35  		return nil, errors.Trace(err)
    36  	}
    37  	var apiCaller base.APICaller
    38  	if err := context.Get(config.APICallerName, &apiCaller); err != nil {
    39  		return nil, errors.Trace(err)
    40  	}
    41  	var agent agent.Agent
    42  	if err := context.Get(config.AgentName, &agent); err != nil {
    43  		return nil, errors.Trace(err)
    44  	}
    45  	agentTag := agent.CurrentConfig().Tag()
    46  	machineTag, ok := agentTag.(names.MachineTag)
    47  	if !ok {
    48  		return nil, errors.New("singular flag expected a machine agent")
    49  	}
    50  
    51  	// TODO(fwereade): model id is implicit in apiCaller, would
    52  	// be better if explicit.
    53  	facade, err := config.NewFacade(apiCaller, machineTag)
    54  	if err != nil {
    55  		return nil, errors.Trace(err)
    56  	}
    57  	flag, err := config.NewWorker(FlagConfig{
    58  		Clock:    clock,
    59  		Facade:   facade,
    60  		Duration: config.Duration,
    61  	})
    62  	if err != nil {
    63  		return nil, errors.Trace(err)
    64  	}
    65  	return flag, nil
    66  }
    67  
    68  // Manifold returns a dependency.Manifold that will run a FlagWorker and
    69  // expose it to clients as a engine.Flag resource.
    70  func Manifold(config ManifoldConfig) dependency.Manifold {
    71  	return dependency.Manifold{
    72  		Inputs: []string{
    73  			config.ClockName,
    74  			config.APICallerName,
    75  			config.AgentName,
    76  		},
    77  		Start:  config.start,
    78  		Output: engine.FlagOutput,
    79  	}
    80  }