mgokv

Documentation

Overview

Package mgokv defines cached MongoDB-backed global persistent storage for key-value pairs.

It is designed to be used when there is a small set of attributes that change infrequently. It shouldn't be used when there's an unbounded set of keys, as key entries are not deleted.

Index

• Variables
• type Session
  • func (s *Session) Get(key string, v interface{}) error
  • func (s *Session) Put(key string, val interface{}) error
  • func (s *Session) PutInitial(key string, val interface{}) (bool, error)
  • func (s *Session) Update(key string, update interface{}) error
• type Store
  • func NewStore(cacheLifetime time.Duration, c *mgo.Collection) *Store
  • func (s *Store) Refresh()
  • func (s *Store) Session(session *mgo.Session) *Session

Variables

var ErrNotFound = errgo.New("persistent data entry not found")

ErrNotFound is returned as the cause of the error when an entry is not found.

Types

type Session

type Session struct {
	*Store
	// contains filtered or unexported fields
}

Session associates a Store instance with a mongo session.

func (*Session) Get

func (s *Session) Get(key string, v interface{}) error

Get gets the value associated with the given key into the value pointed to by v, which should be a pointer to the same struct type used to put the value originally.

If the value is not found, it returns ErrNotFound.

func (*Session) Put

func (s *Session) Put(key string, val interface{}) error

Put stores the given value for the given key. The value must be a struct type that is marshalable as BSON (see http://gopkg.in/mgo.v2/bson).

func (*Session) PutInitial

func (s *Session) PutInitial(key string, val interface{}) (bool, error)

PutInitial puts an initial value for the given key. It does nothing if there is already a value stored for the key. It reports whether the value was actually set.

func (*Session) Update

func (s *Session) Update(key string, update interface{}) error

Update updates the value using the MongoDB update operation specified in update. The value is stored in the "value" field in the document.

For example, if a value of type struct { N int } is associated with a key, then:

s.Update(key, bson.M{"$inc": bson.M{"value.n": 1}})

will atomically increment the N value.

If there is no value associated with the key, Update returns ErrNotFound.

type Store

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

Store represents a cached set of key-value pairs.

func NewStore

func NewStore(cacheLifetime time.Duration, c *mgo.Collection) *Store

NewStore returns a Store that will cache items for at most the given time in the given collection. The session in the collection will not be used - the session passed to Store.Session will be used instead.

func (*Store) Refresh

func (s *Store) Refresh()

Refresh forgets all cached items.

func (*Store) Session

func (s *Store) Session(session *mgo.Session) *Session

Session returns a store session that uses the given session for storage. Each store entry is stored in a document in the collection.