Moneta: A unified interface for key/value stores
Moneta provides a standard interface for interacting with various kinds of key/value stores. A short overview of the features:
- Supports a lot of backends (See below)
- Allows a full configuration of the serialization -> compression -> adapter stack using proxies (Similar to Rack middlewares)
- Configurable serialization via
Moneta::Transformer
proxy (Marshal/JSON/YAML and many more) - Configurable value compression via
Moneta::Transformer
proxy (Zlib, Snappy, LZMA, ...) - Configurable key transformation via
Moneta::Transformer
proxy
- Configurable serialization via
- Expiration for all stores (Added via proxy
Moneta::Expires
if not supported natively) - Atomic incrementation and decrementation for most stores (Method
#increment
and#decrement
) - Includes a very simple key/value server (
Moneta::Server
) and client (Moneta::Adapters::Client
) - Integration with Rails, Rack, Sinatra and Rack-Cache
Moneta is tested thoroughly using Travis-CI.
Links
- Source: http://github.com/minad/moneta
- Bugs: http://github.com/minad/moneta/issues
- API documentation:
- Latest Gem: http://rubydoc.info/gems/moneta/frames
- GitHub master: http://rubydoc.info/github/minad/moneta/master/frames
Supported backends
Out of the box, it supports the following backends:
- Memory:
- In-memory store (
:Memory
) - LRU hash - prefer this over :Memory! (
:LRUHash
) - LocalMemCache (
:LocalMemCache
) - Memcached store (
:Memcached
,:MemcachedNative
and:MemcachedDalli
)
- In-memory store (
- Relational Databases:
- DataMapper (
:DataMapper
) - ActiveRecord (
:ActiveRecord
) - Sequel (
:Sequel
) - Sqlite3 (
:Sqlite
)
- DataMapper (
- Filesystem:
- PStore (
:PStore
) - YAML store (
:YAML
) - Filesystem directory store (
:File
) - Filesystem directory store which spreads files in subdirectories using md5 hash (
:HashFile
)
- PStore (
- Key/value databases:
- Berkeley DB (
:DBM
) - Cassandra (
:Cassandra
) - GDBM (
:GDBM
) - HBase (
:HBase
) - LevelDB (
:LevelDB
) - Redis (
:Redis
) - Riak (
:Riak
) - SDBM (
:SDBM
) - TokyoCabinet (
:TokyoCabinet
)
- Berkeley DB (
- Document databases:
- CouchDB (
:Couch
) - MongoDB (
:Mongo
)
- CouchDB (
- Moneta network protocols:
- Moneta key/value client (
:Client
works withMoneta::Server
) - Moneta HTTP/REST client (
:RestClient
works withRack::MonetaRest
)
- Moneta key/value client (
- Other
- Fog cloud storage which supports Amazon S3, Rackspace, etc. (
:Fog
) - Storage which doesn't store anything (
:Null
)
- Fog cloud storage which supports Amazon S3, Rackspace, etc. (
Some of the backends are not exactly based on key/value stores, e.g. the relational ones. These are useful if you already use the corresponding backend in your application. You get a key/value store for free then without installing any additional services and you still have the possibility to upgrade to a real key/value store.
Proxies
In addition it supports proxies (Similar to Rack middlewares) which add additional features to storage backends:
Moneta::Proxy
andMoneta::Wrapper
proxy base classesMoneta::Expires
to add expiration support to stores which don't support it natively. Add it in the builder usinguse :Expires
.Moneta::Stack
to stack multiple stores (Read returns result from first where the key is found, writes go to all stores). Add it in the builder usinguse :Stack
.Moneta::Transformer
transforms keys and values (Marshal, YAML, JSON, Base64, MD5, ...). Add it in the builder usinguse :Transformer
.Moneta::Cache
combine two stores, one as backend and one as cache (e.g.Moneta::Adapters::File
+Moneta::Adapters::Memory
). Add it in the builder usinguse :Cache
.Moneta::Lock
to make store thread safe. Add it in the builder usinguse :Lock
.Moneta::Logger
to log database accesses. Add it in the builder usinguse :Logger
.Moneta::Shared
to share a store between multiple processes. Add it in the builder usinguse :Shared
.
Supported serializers and compressors (Moneta::Transformer
)
Supported serializers:
- BEncode (
:bencode
) - BERT (
:bert
) - BSON (
:bson
) - JSON (
:json
) - Marshal (
:marshal
) - MessagePack (
:msgpack
) - Ox (
:ox
) - TNetStrings (
:tnet
) - YAML (
:yaml
)
Supported value compressors:
- LZMA (
:lzma
) - LZO (
:lzo
) - Snappy (
:snappy
) - QuickLZ (
:quicklz
) - Zlib (
:zlib
)
Special transformers:
- Digests (MD5, Shas, ...)
- Add prefix to keys (
:prefix
) - HMAC to verify values (
:hmac
, useful forRack::MonetaCookies
)
Moneta API
The Moneta API is purposely extremely similar to the Hash API with a few minor additions.
There are the additional methods #load
, #increment
, #decrement
and #close
. Every method takes also a optional
option hash. In order so support an identical API across stores, Moneta does not support iteration or partial matches.
#initialize(options) options differs per-store, and is used to set up the store.
#[](key) retrieve a key. If the key is not available, return nil.
#load(key, options = {}) retrieve a key. If the key is not available, return nil.
#fetch(key, options = {}, &block) retrieve a key. If the key is not available, execute the
block and return its return value.
#fetch(key, value, options = {}) retrieve a key. If the key is not available, return the value,
#[]=(key, value) set a value for a key. If the key is already used, clobber it.
keys set using []= will never expire.
#store(key, value, options = {}) same as []=, but you can supply options.
#delete(key, options = {}) delete the key from the store and return the current value.
#key?(key, options = {}) true if the key exists, false if it does not.
#increment(key, amount = 1, options = {}) increment numeric value. This is a atomic operation
which is not supported by all stores. Returns current value.
#decrement(key, amount = 1, options = {}) increment numeric value. This is a atomic operation
which is not supported by all stores. Returns current value.
This is just syntactic sugar for incrementing with a negative value.
#clear(options = {}) clear all keys in this store.
#close close database connection.
Creating a Store
There is a simple interface to create a store using Moneta.new
:
store = Moneta.new(:Memcached, :server => 'localhost:11211')
If you want to have control over the proxies, you have to use Moneta.build
:
store = Moneta.build do
# Adds expires proxy
use :Expires
# Transform key using Marshal and Base64 and value using Marshal
use :Transformer, :key => [:marshal, :base64], :value => :marshal
# Memory backend
adapter :Memory
end
Expiration
The Cassandra, Memcached and Redis backends supports expires values directly:
cache = Moneta::Adapters::Memcached.new
# Or using the builder...
cache = Moneta.build do
adapter :Memcached
end
# Expires in 60 seconds
cache.store(key, value, :expires => 60)
# Update expires time if value is found
cache.load(key, :expires => 30)
cache.key?(key, :expires => 30)
You can add the expires feature to other backends using the Expires proxy:
# Using the :expires option
cache = Moneta.new(:File, :dir => '...', :expires => true)
# or manually by using the proxy...
cache = Moneta::Expires.new(Moneta::Adapters::File.new(:dir => '...'))
# or using the builder...
cache = Moneta.build do
use :Expires
adapter :File, :dir => '...'
end
Incrementation and raw access
The stores support the #increment
which allows atomic increments of unsigned integer values. If you increment
a non existing value, it will be created. If you increment a non integer value an exception will be raised.
store.increment('counter') # returns 1, counter created
store.increment('counter') # returns 2
store.increment('counter', -1) # returns 1
store.increment('counter', 13) # returns 14
store.increment('counter', 0) # returns 14
store.decrement('counter') # returns 13
store['name'] = 'Moneta'
store.increment('name') # raises an Exception
If you want to access the counter value you have to use raw access to the datastore. This is only important
if you have a Moneta::Transformer
somewhere in your proxy stack which transforms the values e.g. with Marshal
.
store.increment('counter') # returns 1, counter created
store.load('counter', :raw => true) # returns 1
store.store('counter', '10', :raw => true)
store.increment('counter') # returns 11
Fortunately there is a nicer way to do this using some syntactic sugar!
store.increment('counter') # returns 1, counter created
store.raw['counter'] # returns 1
store.raw.load('counter') # returns 1
store.raw['counter'] = '10'
store.increment('counter') # returns 11
You can also keep the raw
store in a variable and use it like this:
counters = store.raw
counters.increment('counter') # returns 1, counter created
counters['counter'] # returns 1
counters.load('counter') # returns 1
counters['counter'] = '10'
counters.increment('counter') # returns 11
Stores which support incrementation (you have to use Moneta::Lock
if you want to use the store in a multithreading environment.)
- ActiveRecord
- File
- HBase
- LRUHash
- LevelDB
- Memcached
- Memory
- Redis
- SDBM/DBM/GDBM
- Sequel
- Sqlite
- TokyoCabinet
- YAML/PStore
Stores which don't support incrementation:
- Cassandra
- Couch
- DataMapper
- Fog
- LocalMemCache
- Mongo
- Riak
Syntactic sugar and option merger
For raw data access as described before the class Moneta::OptionMerger
is used. It works like this:
# All methods after 'with' get the options passed
store.with(:raw => true).load('key')
# You can also specify the methods
store.with(:raw => true, :only => :load).load('key')
store.with(:raw => true, :except => [:key?, :increment]).load('key')
# Syntactic sugar for raw access
store.raw.load('key')
# Access substore where all keys get a prefix
substore = store.prefix('sub')
substore['key'] = 'value'
store['key'] # returns nil
store['subkey'] # returns 'value'
# Set expiration time for all keys
short_lived_store = store.expires(60)
short_lived_store['key'] = 'value'
Framework Integration
Inspired by redis-store there exist integration classes for Rails, Rack and Rack-Cache. You can also use all the Rack middlewares together with the Sinatra framework. There exist the following integration classes:
- Rack and Sinatra
Rack::Session::Moneta
is a Rack middleware to use Moneta for storing sessionsRack::MonetaStore
is a Rack middleware which places a Moneta store in the environment and enables per-request cachingRack::MonetaCookies
is a Rack middleware which uses Moneta to store cookiesRack::MonetaRest
is a Rack application which exposes a Moneta store via REST/HTTPRack::Cache::Moneta
provides meta and entity stores for Rack-Cache
- Rails
ActionDispatch::Session::MonetaStore
is a Rails middleware to use Moneta for storing sessionsActiveSupport::Cache::MonetaStore
is a Rails cache implementation which uses a Moneta store as backend
Rack session store
You can use Moneta as a Rack session store. Use it in your config.ru
like this:
require 'rack/session/moneta'
# Use only the adapter name
use Rack::Session::Moneta, :store => :Redis
# Use Moneta.new
use Rack::Session::Moneta, :store => Moneta.new(:Memory, :expires => true)
# Use the Moneta builder
use Rack::Session::Moneta do
use :Expires
adapter :Memory
end
Rack Moneta middleware
There is a simple middleware which places a Moneta store in the Rack environment at env['rack.moneta_store']
. It supports per-request
caching if you add the option :cache => true
. Use it in your config.ru
like this:
# Add Rack::MonetaStore somewhere in your rack stack
use Rack::MonetaStore, :Memory, :cache => true
run lambda do |env|
env['rack.moneta_store'] # is a Moneta store with per-request caching
end
# Pass it a block like the one passed to Moneta.build
use Rack::MonetaStore do
use :Transformer, :value => :zlib
adapter :Cookie
end
run lambda do |env|
env['rack.moneta_store'] # is a Moneta store without caching
end
Rack REST server
If you want to expose your Moneta key/value store via HTTP, you can use the Rack/Moneta REST service. Use it in your config.ru
like this:
require 'rack/moneta_rest'
map '/moneta' do
run Rack::MonetaRest.new(:Memory)
end
# Or pass it a block like the one passed to Moneta.build
run Rack::MonetaRest.new do
use :Transformer, :value => :zlib
adapter :Memory
end
Rack cache
You can use Moneta as a Rack-Cache store. Use it in your config.ru
like this:
require 'rack/cache/moneta'
use Rack::Cache,
:metastore => 'moneta://Memory?expires=true',
:entitystore => 'moneta://Memory?expires=true'
# Or used named Moneta stores
Rack::Cache::Moneta['named_metastore'] = Moneta.build do
use :Expires
adapter :Memory
end
use Rack::Cache,
:metastore => 'moneta://named_metastore',
:entity_store => 'moneta://named_entitystore'
Rack cookies
Use Moneta to store cookies in Rack. It uses the Moneta::Adapters::Cookie
. You might
wonder what the purpose of this store or Rack middleware is: It makes it possible
to use all the transformers on the cookies (e.g. :prefix
, :marshal
and :hmac
for value verification).
require 'rack/moneta_cookies'
use Rack::MonetaCookies, :domain => 'example.com', :path => '/path'
run lambda do |env|
req = Rack::Request.new(env)
req. #=> is now a Moneta store!
env['rack.request.cookie_hash'] #=> is now a Moneta store!
req.['key'] #=> retrieves 'key'
req.['key'] = 'value' #=> sets 'key'
req..delete('key') #=> removes 'key'
[200, {}, []]
end
Rails session store
Add the session store in your application configuration config/environments/*.rb
.
require 'moneta'
# Only by adapter name
config.cache_store :moneta_store, :store => :Memory
# Use Moneta.new
config.cache_store :moneta_store, :store => Moneta.new(:Memory)
# Use the Moneta builder
config.cache_store :moneta_store, :store => Moneta.build do
use :Expires
adapter :Memory
end
Rails cache store
Add the cache store in your application configuration config/environments/*.rb
. Unfortunately the
Moneta cache store doesn't support matchers. If you need these features use a different server-specific implementation.
require 'moneta'
# Only by adapter name
config.cache_store :moneta_store, :store => :Memory
# Use Moneta.new
config.cache_store :moneta_store, :store => Moneta.new(:Memory)
# Use the Moneta builder
config.cache_store :moneta_store, :store => Moneta.build do
use :Expires
adapter :Memory
end
Advanced
Build your own key value server
You can use Moneta to build your own key/value server which is shared between
multiple processes. If you run the following code in two different processes,
they will share the same data which will also be persistet in the database shared.db
.
require 'moneta'
store = Moneta.build do
use :Transformer, :key => :marshal, :value => :marshal
use :Shared do
use :Cache do
cache do
adapter :LRUHash
end
backend do
adapter :GDBM, :file => 'shared.db'
end
end
end
end
If you want to go further, you might want to take a look at Moneta::Server
and Moneta::Adapters::Client
which
are used by Moneta::Shared
and provide the networking communication. But be aware that they are experimental
and subjected to change. They provide an acceptable performance (for being ruby only), but don't have a stable protocol yet.
You might wonder why I didn't use DRb to implement server and client - in fact my first versions used it, but with much worse performance and it was real fun to implement the networking directly :) There is still much room for improvement and experiments, try EventMachine, try Kgio, ...
ToyStore ORM
If you want something more advanced to handle your objects and relations,
use John Nunemaker's ToyStore which works
together with Moneta. Assuming that Person
is a ToyStore::Object
you can
add persistence using Moneta as follows:
# Use the Moneta Redis backend
Person.adapter :memory, Moneta.new(:Redis)
Testing and Benchmarks
Testing is done using Travis-CI. Currently we support Ruby 1.8.7 and 1.9.3.
Benchmarks for each store are done on Travis-CI for each build. Take a look there to compare the speed of the different key value stores for different key/value sizes and size distributions. Feel free to add your own configurations! The impact of Moneta should be minimal since it is only a thin layer on top of the different stores.
More information
- http://yehudakatz.com/2009/02/12/whats-the-point/
- http://yehudakatz.com/2009/02/12/initial-release-of-moneta-unified-keyvalue-store-api/
Alternatives
- Horcrux: Used at github, supports batch operations but only Memcached backend
- ToyStore: ORM mapper for key/value stores
- ToyStore Adapter: Adapter to key/value stores used by ToyStore, Moneta can be used directly with the ToyStore Memory adapter
Authors
- Daniel Mendler
- Hannes Georg
- Originally by Yehuda Katz and contributors