github.com/cloud-green/juju@v0.0.0-20151002100041-a00291338d3d/worker/uniter/resolver/interface.go (about)

     1  // Copyright 2015 Canonical Ltd.
     2  // Licensed under the AGPLv3, see LICENCE file for details.
     3  
     4  package resolver
     5  
     6  import (
     7  	"github.com/juju/errors"
     8  	"gopkg.in/juju/charm.v6-unstable"
     9  
    10  	"github.com/juju/juju/worker/uniter/operation"
    11  	"github.com/juju/juju/worker/uniter/remotestate"
    12  )
    13  
    14  // ErrNoOperation is used to indicate that there are no
    15  // currently pending operations to run.
    16  var ErrNoOperation = errors.New("no operations")
    17  
    18  // ErrWaiting indicates that the resolver loop should
    19  // not execute any more operations until a remote state
    20  // event has occurred.
    21  var ErrWaiting = errors.New("waiting for remote state change")
    22  
    23  // ErrRestart indicates that the resolver loop should
    24  // be restarted with a new remote state watcher.
    25  var ErrRestart = errors.New("restarting resolver")
    26  
    27  // ErrTerminate is used when the unit has been marked
    28  // as dead and so there will never be any more
    29  // operations to run for that unit.
    30  var ErrTerminate = errors.New("terminate resolver")
    31  
    32  // Resolver instances use local (as is) and remote (to be) state
    33  // to provide operations to run in order to progress towards
    34  // the desired state.
    35  type Resolver interface {
    36  	// NextOp returns the next operation to run to reconcile
    37  	// the local state with the remote, desired state. The
    38  	// operations returned must be created using the given
    39  	// operation.Factory.
    40  	//
    41  	// This method must return ErrNoOperation if there are no
    42  	// operations to perform.
    43  	//
    44  	// By returning ErrTerminate, the resolver indicates that
    45  	// it will never have any more operations to perform,
    46  	// and the caller can cease calling.
    47  	NextOp(
    48  		LocalState,
    49  		remotestate.Snapshot,
    50  		operation.Factory,
    51  	) (operation.Operation, error)
    52  }
    53  
    54  type LocalState struct {
    55  	operation.State
    56  
    57  	// CharmURL reports the currently installed charm URL. This is set
    58  	// by the committing of deploy (install/upgrade) ops.
    59  	CharmURL *charm.URL
    60  
    61  	// Conflicted indicates that the uniter is in a conflicted state,
    62  	// and needs either resolution or a forced upgrade to continue.
    63  	Conflicted bool
    64  
    65  	// Restart indicates that the resolver should exit with ErrRestart
    66  	// at the earliest opportunity.
    67  	Restart bool
    68  
    69  	// UpdateStatusVersion is the version of update status from remotestate.Snapshot
    70  	// for which an update-status hook has been committed.
    71  	UpdateStatusVersion int
    72  
    73  	// ConfigVersion is the version of config from remotestate.Snapshot
    74  	// for which a config-changed hook has been committed.
    75  	ConfigVersion int
    76  
    77  	// LeaderSettingsVersion is the version of leader settings from
    78  	// remotestate.Snapshot for which a leader-settings-changed hook has
    79  	// been committed.
    80  	LeaderSettingsVersion int
    81  
    82  	// CompletedActions is the set of actions that have been completed.
    83  	// This is used to prevent us re running actions requested by the
    84  	// state server.
    85  	CompletedActions map[string]struct{}
    86  }