github.com/makyo/juju@v0.0.0-20160425123129-2608902037e9/api/uniter/relation.go (about)

     1  // Copyright 2013 Canonical Ltd.
     2  // Licensed under the AGPLv3, see LICENCE file for details.
     3  
     4  package uniter
     5  
     6  import (
     7  	"fmt"
     8  
     9  	"github.com/juju/names"
    10  
    11  	"github.com/juju/juju/apiserver/params"
    12  )
    13  
    14  // This module implements a subset of the interface provided by
    15  // state.Relation, as needed by the uniter API.
    16  
    17  // Relation represents a relation between one or two service
    18  // endpoints.
    19  type Relation struct {
    20  	st   *State
    21  	tag  names.RelationTag
    22  	id   int
    23  	life params.Life
    24  }
    25  
    26  // Tag returns the relation tag.
    27  func (r *Relation) Tag() names.RelationTag {
    28  	return r.tag
    29  }
    30  
    31  // String returns the relation as a string.
    32  func (r *Relation) String() string {
    33  	return r.tag.Id()
    34  }
    35  
    36  // Id returns the integer internal relation key. This is exposed
    37  // because the unit agent needs to expose a value derived from this
    38  // (as JUJU_RELATION_ID) to allow relation hooks to differentiate
    39  // between relations with different services.
    40  func (r *Relation) Id() int {
    41  	return r.id
    42  }
    43  
    44  // Life returns the relation's current life state.
    45  func (r *Relation) Life() params.Life {
    46  	return r.life
    47  }
    48  
    49  // Refresh refreshes the contents of the relation from the underlying
    50  // state. It returns an error that satisfies errors.IsNotFound if the
    51  // relation has been removed.
    52  func (r *Relation) Refresh() error {
    53  	result, err := r.st.relation(r.tag, r.st.unitTag)
    54  	if err != nil {
    55  		return err
    56  	}
    57  	// NOTE: The life cycle information is the only
    58  	// thing that can change - id, tag and endpoint
    59  	// information are static.
    60  	r.life = result.Life
    61  
    62  	return nil
    63  }
    64  
    65  // Endpoint returns the endpoint of the relation for the service the
    66  // uniter's managed unit belongs to.
    67  func (r *Relation) Endpoint() (*Endpoint, error) {
    68  	// NOTE: This differs from state.Relation.Endpoint(), because when
    69  	// talking to the API, there's already an authenticated entity - the
    70  	// unit, and we can find out its service name.
    71  	result, err := r.st.relation(r.tag, r.st.unitTag)
    72  	if err != nil {
    73  		return nil, err
    74  	}
    75  	return &Endpoint{result.Endpoint.Relation}, nil
    76  }
    77  
    78  // Unit returns a RelationUnit for the supplied unit.
    79  func (r *Relation) Unit(u *Unit) (*RelationUnit, error) {
    80  	if u == nil {
    81  		return nil, fmt.Errorf("unit is nil")
    82  	}
    83  	result, err := r.st.relation(r.tag, u.tag)
    84  	if err != nil {
    85  		return nil, err
    86  	}
    87  	return &RelationUnit{
    88  		relation: r,
    89  		unit:     u,
    90  		endpoint: Endpoint{result.Endpoint.Relation},
    91  		st:       r.st,
    92  	}, nil
    93  }