github.com/niedbalski/juju@v0.0.0-20190215020005-8ff100488e47/worker/credentialvalidator/manifold.go (about)

     1  // Copyright 2018 Canonical Ltd.
     2  // Licensed under the AGPLv3, see LICENCE file for details.
     3  
     4  package credentialvalidator
     5  
     6  import (
     7  	"github.com/juju/errors"
     8  	"gopkg.in/juju/worker.v1"
     9  	"gopkg.in/juju/worker.v1/dependency"
    10  
    11  	"github.com/juju/juju/api/base"
    12  	"github.com/juju/juju/cmd/jujud/agent/engine"
    13  )
    14  
    15  // ManifoldConfig holds the dependencies and configuration for a
    16  // Worker manifold.
    17  type ManifoldConfig struct {
    18  	APICallerName string
    19  
    20  	NewFacade func(base.APICaller) (Facade, error)
    21  	NewWorker func(Config) (worker.Worker, error)
    22  }
    23  
    24  // Validate is called by start to check for bad configuration.
    25  func (config ManifoldConfig) Validate() error {
    26  	if config.APICallerName == "" {
    27  		return errors.NotValidf("empty APICallerName")
    28  	}
    29  	if config.NewFacade == nil {
    30  		return errors.NotValidf("nil NewFacade")
    31  	}
    32  	if config.NewWorker == nil {
    33  		return errors.NotValidf("nil NewWorker")
    34  	}
    35  	return nil
    36  }
    37  
    38  // start is a StartFunc for a Worker manifold.
    39  func (config ManifoldConfig) start(context dependency.Context) (worker.Worker, error) {
    40  	if err := config.Validate(); err != nil {
    41  		return nil, errors.Trace(err)
    42  	}
    43  	var apiCaller base.APICaller
    44  	if err := context.Get(config.APICallerName, &apiCaller); err != nil {
    45  		return nil, errors.Trace(err)
    46  	}
    47  	facade, err := config.NewFacade(apiCaller)
    48  	if err != nil {
    49  		return nil, errors.Trace(err)
    50  	}
    51  	w, err := config.NewWorker(Config{
    52  		Facade: facade,
    53  	})
    54  	if err != nil {
    55  		return nil, errors.Trace(err)
    56  	}
    57  	return w, nil
    58  }
    59  
    60  // Manifold packages a Worker for use in a dependency.Engine.
    61  func Manifold(config ManifoldConfig) dependency.Manifold {
    62  	return dependency.Manifold{
    63  		Inputs: []string{config.APICallerName},
    64  		Start:  config.start,
    65  		Output: engine.FlagOutput,
    66  		Filter: filterErrors,
    67  	}
    68  }
    69  
    70  func filterErrors(err error) error {
    71  	cause := errors.Cause(err)
    72  	if cause == ErrValidityChanged ||
    73  		cause == ErrModelCredentialChanged {
    74  		return dependency.ErrBounce
    75  	}
    76  	return err
    77  }