github.com/niedbalski/juju@v0.0.0-20190215020005-8ff100488e47/cmd/jujud/agent/engine/agent.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/agent"
    11  )
    12  
    13  // Some manifolds just depend on an agent; this type configures them.
    14  type AgentManifoldConfig struct {
    15  	AgentName string
    16  }
    17  
    18  // AgentStartFunc encapsulates the behaviour that varies among AgentManifolds.
    19  type AgentStartFunc func(agent.Agent) (worker.Worker, error)
    20  
    21  // AgentManifold returns a dependency.Manifold that calls the supplied start
    22  // func with the agent resource defined in the config (once it's present).
    23  func AgentManifold(config AgentManifoldConfig, start AgentStartFunc) dependency.Manifold {
    24  	return dependency.Manifold{
    25  		Inputs: []string{
    26  			config.AgentName,
    27  		},
    28  		Start: func(context dependency.Context) (worker.Worker, error) {
    29  			var agent agent.Agent
    30  			if err := context.Get(config.AgentName, &agent); err != nil {
    31  				return nil, err
    32  			}
    33  			return start(agent)
    34  		},
    35  	}
    36  }