redis-dirty-hash-js

A wrapper class for Redis hashes that performs dirty tracking. Not quite an ORM, but caches data locally, and only persists new changes.

Examples

RedisDirtyHash = require('redis_dirty_hash');
hash = new RedisDirtyHash({redis: redisClient, key: 'myHash'});

// Javascript POD will be serialized and deserialized using JSON
hash.set({name: 'John', occupation: 'baker', age: 30, hobbies: ['stamps', 'golf']});

hash.persist(function(err) {
  hash.set({name: 'John', occupation: 'hatter'});

  // This will only persist the change to the `occupation` property.
  hash.persist();
});

API

constructor(options)

Creates a new RedisDirtyHash object. Options include:

• redis (required) A Redis client.
• key (required) The key of the Redis hash.
• shouldDeleteOnPersist(key, value) A callback that determines whether a dirty value should be deleted from the hash via HDEL. By default, keys whose values are set to undefined will be deleted from Redis.
• serialize(key, value) A callback that converts values to strings that will be persisted to Redis. By default, values will be JSON-serialized.
• deserialize(key, value) A callback the converts string values from Redis into JavaScript runtime values. By default, strings will be JSON-parsed.

#get(key)

Retrieve the value of a specific key in the hash.

#get([key1, key2, ...])

Retrieve values for a list of keys in the hash. Returns a JavaScript object that maps the specified keys to their respective values.

#set(key, value)

Sets the value of a specified key. Does not persist to Redis, but marks the key as dirty if the value changed, so it will be persisted the next time #persist is called.

If you want to clear a key from Redis, set its value to undefined.

#set({key1: value1, key2: value2, ...})

Sets the values of the specified keys. Does not persist to Redis, but marks any changed key as dirty, so it will be persisted the next time #persist is called.

If you want to clear a key from Redis, set its value to undefined.

#persist(callback)

Writes changes to Redis.

#fetch(callback)

Retrieves all keys from Redis. This will clobber any local changes to the keys.

#destroy(callback)

Destroys the entire hash in Redis. This will not clear internal properties, but it will set them as dirty, so they will be persisted the next time #persist is called.

#isPersisted()

Returns true if the values in the hash have been persisted to or retrieved from Redis, regardless of new changes.

#isDirty(key)

Returns whether the value for the given key will be persisted the next time #persist is called.