lock

Documentation

Overview

Package lock provides a mechanism for distributed locks. Several instances of components (same component name, different component IDs) can compete to execute Jobs. We want that a given job (recognised by its job name) is executed only once at a time. To achive that we use CockroachDB, a distributed ACID DB. Each component will execute a transaction to lock the job, the transaction that succeed will obtain the lock, and the component can execute the corresponding job. Also, when a lock is disabled, the Lock method will always return an ErrDisabled error.

Index

• type ErrDisabled
  • func (e *ErrDisabled) Error() string
• type ErrUnauthorised
  • func (e *ErrUnauthorised) Error() string
• type LocalLock
  • func NewLocalLock() *LocalLock
  • func (l *LocalLock) Lock() error
  • func (l *LocalLock) Unlock() error
• type Lock
  • func New(s Storage) *Lock
  • func (l *Lock) Disable(componentName, jobName string) error
  • func (l *Lock) Enable(componentName, jobName string) error
  • func (l *Lock) Lock(componentName, componentID, jobName, jobID string, ...) error
  • func (l *Lock) Unlock(componentName, componentID, jobName, jobID string) error
• type NoopLocker
  • func (l *NoopLocker) Disable(componentName, jobName string) error
  • func (l *NoopLocker) Enable(componentName, jobName string) error
  • func (l *NoopLocker) Lock(componentName, componentID, jobName, jobID string, ...) error
  • func (l *NoopLocker) Unlock(componentName, componentID, jobName, jobID string) error
• type Storage

Types

type ErrDisabled

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

ErrDisabled is the error returned when the lock is disabled.

func (*ErrDisabled) Error

func (e *ErrDisabled) Error() string

type ErrUnauthorised

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

ErrUnauthorised is the error returned when there is a call to the Lock method, but there is already another component owning the lock.

func (*ErrUnauthorised) Error

func (e *ErrUnauthorised) Error() string

type LocalLock

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

LocalLock is the local lock

func NewLocalLock

func NewLocalLock() *LocalLock

NewLocalLock returns a lock local, that is a lock that does not use the distributed Storage to assure that only one instance of the job is running in the cluster.

func (*LocalLock) Lock

func (l *LocalLock) Lock() error

Lock locks locally.

func (*LocalLock) Unlock

func (l *LocalLock) Unlock() error

Unlock unlocks locally.

type Lock

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

Lock is the locking module.

func New

func New(s Storage) *Lock

New returns a new locking module.

func (*Lock) Disable

func (l *Lock) Disable(componentName, jobName string) error

Disable disable the job. It sets the 'enabled' boolean to false for the current job.

func (*Lock) Enable

func (l *Lock) Enable(componentName, jobName string) error

Enable enable the job. It sets the 'enabled' boolean to true for the current job.

func (*Lock) Lock

func (l *Lock) Lock(componentName, componentID, jobName, jobID string, jobMaxDuration time.Duration) error

Lock try to reserve and lock the job in the distributed DB. It returns a nil error if the reservation succeeded, and an error if it didn't.

func (*Lock) Unlock

func (l *Lock) Unlock(componentName, componentID, jobName, jobID string) error

Unlock unlocks the lock in the distributed DB. A job can be unlocked it it is disabled. Unlock returns a nil error if the operation succeeded, and an error if it didn't.

type NoopLocker

type NoopLocker struct{}

NoopLocker is a lock that does nothing, it always accept lock requests. It should be used when no lock is required.

func (*NoopLocker) Disable

func (l *NoopLocker) Disable(componentName, jobName string) error

Disable does nothing.

func (*NoopLocker) Enable

func (l *NoopLocker) Enable(componentName, jobName string) error

Enable does nothing.

func (*NoopLocker) Lock

func (l *NoopLocker) Lock(componentName, componentID, jobName, jobID string, jobMaxDuration time.Duration) error

Lock does nothing.

func (*NoopLocker) Unlock

func (l *NoopLocker) Unlock(componentName, componentID, jobName, jobID string) error

Unlock does nothing.

type Storage

type Storage interface {
	Exec(query string, args ...interface{}) (sql.Result, error)
	QueryRow(query string, args ...interface{}) *sql.Row
}

Storage is the interface of the database.