github.com/mwhudson/juju@v0.0.0-20160512215208-90ff01f3497f/worker/uniter/charm/charm.go (about)

     1  // Copyright 2012-2014 Canonical Ltd.
     2  // Licensed under the AGPLv3, see LICENCE file for details.
     3  
     4  package charm
     5  
     6  import (
     7  	"errors"
     8  
     9  	"github.com/juju/loggo"
    10  	"github.com/juju/utils"
    11  	"github.com/juju/utils/set"
    12  	"gopkg.in/juju/charm.v6-unstable"
    13  )
    14  
    15  var logger = loggo.GetLogger("juju.worker.uniter.charm")
    16  
    17  // CharmURLPath is the path within a charm directory to which Deployers
    18  // commonly write the charm URL of the latest deployed charm.
    19  const CharmURLPath = ".juju-charm"
    20  
    21  // Bundle allows access to a charm's files.
    22  type Bundle interface {
    23  
    24  	// Manifest returns a set of slash-separated strings representing files,
    25  	// directories, and symlinks stored in the bundle.
    26  	Manifest() (set.Strings, error)
    27  
    28  	// ExpandTo unpacks the entities referenced in the manifest into the
    29  	// supplied directory. If it returns without error, every file referenced
    30  	// in the charm must be present in the directory; implementations may vary
    31  	// in the details of what they do with other files present.
    32  	ExpandTo(dir string) error
    33  }
    34  
    35  // BundleInfo describes a Bundle.
    36  type BundleInfo interface {
    37  
    38  	// URL returns the charm URL identifying the bundle.
    39  	URL() *charm.URL
    40  
    41  	// ArchiveSha256 returns the hex-encoded SHA-256 digest of the bundle data.
    42  	ArchiveSha256() (string, error)
    43  }
    44  
    45  // BundleReader provides a mechanism for getting a Bundle from a BundleInfo.
    46  type BundleReader interface {
    47  
    48  	// Read returns the bundle identified by the supplied info. The abort chan
    49  	// can be used to notify an implementation that it need not complete the
    50  	// operation, and can immediately error out if it is convenient to do so.
    51  	Read(bi BundleInfo, abort <-chan struct{}) (Bundle, error)
    52  }
    53  
    54  // Deployer is responsible for installing and upgrading charms.
    55  type Deployer interface {
    56  
    57  	// Stage must be called to prime the Deployer to install or upgrade the
    58  	// bundle identified by the supplied info. The abort chan can be used to
    59  	// notify an implementation that it need not complete the operation, and
    60  	// can immediately error out if it convenient to do so. It must always
    61  	// be safe to restage the same bundle, or to stage a new bundle.
    62  	Stage(info BundleInfo, abort <-chan struct{}) error
    63  
    64  	// Deploy will install or upgrade the most recently staged bundle.
    65  	// Behaviour is undefined if Stage has not been called. Failures that
    66  	// can be resolved by user intervention will be signalled by returning
    67  	// ErrConflict.
    68  	Deploy() error
    69  
    70  	// NotifyRevert must be called when a conflicted deploy is abandoned, in
    71  	// preparation for a new upgrade.
    72  	NotifyRevert() error
    73  
    74  	// NotifyResolved must be called when the cause of a deploy conflict has
    75  	// been resolved, and a new deploy attempt will be made.
    76  	NotifyResolved() error
    77  }
    78  
    79  // ErrConflict indicates that an upgrade failed and cannot be resolved
    80  // without human intervention.
    81  var ErrConflict = errors.New("charm upgrade has conflicts")
    82  
    83  // ReadCharmURL reads a charm identity file from the supplied path.
    84  func ReadCharmURL(path string) (*charm.URL, error) {
    85  	surl := ""
    86  	if err := utils.ReadYaml(path, &surl); err != nil {
    87  		return nil, err
    88  	}
    89  	return charm.ParseURL(surl)
    90  }
    91  
    92  // WriteCharmURL writes a charm identity file into the supplied path.
    93  func WriteCharmURL(path string, url *charm.URL) error {
    94  	return utils.WriteYaml(path, url.String())
    95  }