github.com/niedbalski/juju@v0.0.0-20190215020005-8ff100488e47/cmd/jujud/agent/engine/api.go (about)

     1  // Copyright 2016 Canonical Ltd.
     2  // Licensed under the AGPLv3, see LICENCE file for details.
     3  
     4  package engine
     5  
     6  import (
     7  	"gopkg.in/juju/worker.v1"
     8  	"gopkg.in/juju/worker.v1/dependency"
     9  
    10  	"github.com/juju/juju/api/base"
    11  )
    12  
    13  // Some (hopefully growing number of) manifolds completely depend on an API
    14  // connection; this type configures them.
    15  type APIManifoldConfig struct {
    16  	APICallerName string
    17  }
    18  
    19  // APIStartFunc encapsulates the behaviour that varies among APIManifolds.
    20  type APIStartFunc func(base.APICaller) (worker.Worker, error)
    21  
    22  // APIManifold returns a dependency.Manifold that calls the supplied start
    23  // func with the API resource defined in the config (once it's present).
    24  func APIManifold(config APIManifoldConfig, start APIStartFunc) dependency.Manifold {
    25  	return dependency.Manifold{
    26  		Inputs: []string{
    27  			config.APICallerName,
    28  		},
    29  		Start: func(context dependency.Context) (worker.Worker, error) {
    30  			var apiCaller base.APICaller
    31  			if err := context.Get(config.APICallerName, &apiCaller); err != nil {
    32  				return nil, err
    33  			}
    34  			return start(apiCaller)
    35  		},
    36  	}
    37  }