overlord

package
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 Go to latest Published: Feb 18, 2016 License: GPL-3.0 Imports: 2 Imported by: 0

Documentation

Overview

Package overlord implements the policies for state transitions for the operation of a snappy system.

Index

Constants

This section is empty.

Variables

This section is empty.

Functions

func WriteState 

func WriteState(s *State, w io.Writer) error

WriteState serializes the provided state into w.

Types

type AssertManager 

type AssertManager struct {
	// contains filtered or unexported fields
}

AssertManager is responsible for the enforcement of assertions in system states. It manipulates observed states to ensure nothing in them violates existing assertions, or misses required ones.

func NewAssertManager 

func NewAssertManager(o *Overlord) (*AssertManager, error)

NewAssertManager returns a new assertion manager.

func (*AssertManager) Apply 

func (m *AssertManager) Apply(s *State) error

Apply implements StateManager.Apply.

func (*AssertManager) Delta 

func (m *AssertManager) Delta(a, b *State) (Delta, error)

Delta implements StateManager.Delta.

func (*AssertManager) Learn 

func (m *AssertManager) Learn(s *State) error

Learn implements StateManager.Learn.

func (*AssertManager) Sanitize 

func (m *AssertManager) Sanitize(s *State) error

Sanitize implements StateManager.Sanitize.

type Delta 

type Delta []DeltaItem

Delta represents a list of state changes.

func (Delta) MarshalText 

func (d Delta) MarshalText() ([]byte, error)

MarshalText returns a human-oriented textual representation of the delta.

This function turns Delta into an encoding.TextMarshaler.

type DeltaItem 

type DeltaItem struct {
	Header  string // Header for grouping
	Summary string // Summary with textual description
	Reason  string // Optional reason for the change, available with sanitization
}

DeltaItem represent a single state change, possibly with a reason for it.

type Overlord 

type Overlord struct {
	// contains filtered or unexported fields
}

Overlord is the central manager of a snappy system, keeping track of all available state managers and related helpers.

func New 

func New() (*Overlord, error)

New creates a new Overlord with all its state managers.

func (*Overlord) AssertManager 

func (o *Overlord) AssertManager() *AssertManager

AssertManager returns the assertion manager enforcing assertions under the overlord.

func (*Overlord) SkillManager 

func (o *Overlord) SkillManager() *SkillManager

SkillManager returns the skill manager mantaining skill assignments under the overlord.

func (*Overlord) SnapManager 

func (o *Overlord) SnapManager() *SnapManager

SnapManager returns the snap manager responsible for snaps under the overlord.

func (*Overlord) StateJournal 

func (o *Overlord) StateJournal() *StateJournal

StateJournal returns the StateJournal used by the overlord.

type SkillManager 

type SkillManager struct {
	// contains filtered or unexported fields
}

SkillManager is responsible for the maintenance of skills in system states. It maintains skills assignments, and also observes installed snaps to track the current set of available skills and skill slots.

func NewSkillManager 

func NewSkillManager(o *Overlord) (*SkillManager, error)

NewSkillManager returns a new SkillManager.

func (*SkillManager) Apply 

func (m *SkillManager) Apply(s *State) error

Apply implements StateManager.Apply.

func (*SkillManager) Delta 

func (m *SkillManager) Delta(a, b *State) (Delta, error)

Delta implements StateManager.Delta.

func (*SkillManager) Grant 

func (m *SkillManager) Grant(s *State, skillSnap, skillName, slotSnap, slotName string) error

Grant records the intent of granting the skill in state s.

func (*SkillManager) Learn 

func (m *SkillManager) Learn(s *State) error

Learn implements StateManager.Learn.

func (*SkillManager) Revoke 

func (m *SkillManager) Revoke(s *State, skillSnap, skillName, slotSnap, slotName string) error

Revoke records the intent of revoking the skill in state s.

func (*SkillManager) Sanitize 

func (m *SkillManager) Sanitize(s *State) error

Sanitize implements StateManager.Sanitize.

type SnapManager 

type SnapManager struct {
	// contains filtered or unexported fields
}

SnapManager is responsible for the installation and removal of snaps.

func NewSnapManager 

func NewSnapManager(o *Overlord) (*SnapManager, error)

NewSnapManager returns a new snap manager.

func (*SnapManager) Apply 

func (m *SnapManager) Apply(s *State) error

Apply implements StateManager.Apply.

func (*SnapManager) Delta 

func (m *SnapManager) Delta(a, b *State) (Delta, error)

Delta implements StateManager.Delta.

func (*SnapManager) Install 

func (m *SnapManager) Install(s *State, snap string) error

Install records the intent of installing snap in state s.

func (*SnapManager) Learn 

func (m *SnapManager) Learn(s *State) error

Learn implements StateManager.Learn.

func (*SnapManager) Remove 

func (m *SnapManager) Remove(s *State, snap string) error

Remove records the intent of removing snap in state s.

func (*SnapManager) Sanitize 

func (m *SnapManager) Sanitize(s *State) error

Sanitize implements StateManager.Sanitize.

type State 

type State struct{}

State represents a snapshot of the system state.

func ReadState 

func ReadState(r io.Reader) (*State, error)

ReadState returns the state deserialized from r.

func (*State) Copy 

func (s *State) Copy() *State

Copy returns an indepent copy of the state.

func (*State) Get 

func (s *State) Get(key string, value interface{})

Get unmarshals the stored value associated with the provided key into the value parameter.

func (*State) Set 

func (s *State) Set(key string, value interface{})

Set associates value with key for future consulting by managers. The provided value must properly marshal and unmarshal with encoding/json.

type StateEngine 

type StateEngine struct{}

StateEngine controls the dispatching of state changes to state managers.

The operations performed by StateEngine resemble in some ways a transaction system, but it needs to deal with the fact that many of the system changes involved in a snappy system are not atomic, and may actually become invalid without notice (e.g. USB device physically removed).

func NewStateEngine 

func NewStateEngine() *StateEngine

NewStateEngine returns a new state engine.

func (*StateEngine) AddManager 

func (se *StateEngine) AddManager(m StateManager)

AddManager adds the provided manager to take part in state operations.

func (*StateEngine) Apply 

func (se *StateEngine) Apply(s *State) error

Apply attempts to perform the necessary changes in the system to make s the current state.

func (*StateEngine) Delta 

func (se *StateEngine) Delta(a, b *State) (Delta, error)

Delta returns the differences between state a and b, or nil if there are no relevant differences.

func (*StateEngine) Learn 

func (se *StateEngine) Learn(s *State) error

Learn records the current state into s.

func (*StateEngine) Sanitize 

func (se *StateEngine) Sanitize(s *State) (Delta, error)

Sanitize attempts to make the necessary changes in the provided state to make it ready for applying. It returns a Delta with the changes performed and the reasoning for them.

func (*StateEngine) Validate 

func (se *StateEngine) Validate(s *State) error

Validate checks whether the s state might be applied as-is if desired. It's implemented in terms of Sanitize and Delta.

type StateJournal 

type StateJournal struct {
	// contains filtered or unexported fields
}

StateJournal is responsible for keeping track of multiple states persistently and recording intended state changes so that the system may be properly recovered from an interruption by moving into the intended state completely, or retroceding to a prior good state.

func NewStateJournal 

func NewStateJournal(engine *StateEngine, dir string) (*StateJournal, error)

NewStateJournal returns a new state journal using dir as its configuration directory.

func (*StateJournal) Commit 

func (j *StateJournal) Commit(s *State) error

Commit attempts to apply the s state, recording it in the journal first to ensure the operation may be continued later if necessary.

func (*StateJournal) Current 

func (j *StateJournal) Current() (*State, error)

Current returns the current system state.

func (*StateJournal) Pending 

func (j *StateJournal) Pending() (*State, error)

Pending returns the last attempted but unfinished commit, if any. It returns ErrNotPending if there are no pending states.

func (*StateJournal) Recover 

func (j *StateJournal) Recover() error

Recover attempts to apply the currently pending state, if any. If applying the pending state fails for any reason and there's a previous good state, applying that will be attempted instead.

func (*StateJournal) Revert 

func (j *StateJournal) Revert() error

Revert attempts to revert the system to the previous known good state, whether the current state is valid or not. This is unlike Recover in that it ignores whether a pending state exists.

type StateManager 

type StateManager interface {
	Apply(s *State) error
	Learn(s *State) error
	Sanitize(s *State) error
	Delta(a, b *State) (Delta, error)
}

StateManager is implemented by types responsible for observing the system state and directly manipulating it.

See the interface of StateEngine for details on those methods.

Source Files

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