jmemcached

This is a Java implementation of the daemon (server) side of the memcached protocol.

Memcache is a network accessible key/value storage system, often used as a distributed cache.

Jmemcached is functionally equivalent in most respects to (native code) memcached, but is written in pure Java, and is thus suitable for:

Portable or Java-only distributions of applications
Embedding inside applications
Integration testing

What would I use it for?

A distributed client/server style cache. Some people use memcached to reduce load on their database. Some people just use it to share data across a cluster. It's simple and common. It's a good general purpose network available cache to compliment any network available service.

Tell me more details...

Ok.

It is implemented in, and requires at least Java 5.
It is protocol compatible with the C version of memcached. Existing clients, including the ones for Java (1 & 2), should work without modification. Replacing the Java version with the C version (and vice versa) is trivial.
Jmemcached supports both the ASCII and binary memcache protocols.
It can be embedded in your existing Java project. (For example hosted by a web application or by an OSGI bundle.)
... or it can be used from the command line interface, with commands roughly switch compatible with the C version.
... or it can be configured using your favourite dependency injection framework (like Spring, PicoContainer, etc.)
It uses JBoss Netty for non-blocking, scalable (Java NIO) network I/O.
While it is slower than the C version, it is still quite fast and suitable for most applications.
The cache portion of the project can be used independently of the daemon so that local process users can have quick low-overhead access to the cache while maintaining the client-server relationship for external clients.
The storage for the cache is abstracted so it should be possible to replace it with other cache implementations (such as OSCache, EHCache, etc.) if that is appropriate.
Cache storage can be handled either by the Java (garbage collected) heap, or, if more storage is required, in a separate memory-mapped file.

How do I use it?

There are two ways; programmatically (embedded inside your application) or using the command-line (CLI) interface.

For programmatic example, here's a snippet from the source for the main class for the CLI:

        // create daemon and start it
        final MemCacheDaemon<LocalCacheElement> daemon = new MemCacheDaemon<LocalCacheElement>();

        CacheStorage<Key, LocalCacheElement> storage = ConcurrentLinkedHashMap.create(ConcurrentLinkedHashMap.EvictionPolicy.FIFO, maxItems, maxBytes);
        daemon.setCache(new CacheImpl(storage));
        daemon.setBinary(binary);
        daemon.setAddr(addr);
        daemon.setIdleTime(idle);
        daemon.setVerbose(verbose);
        daemon.start();

To use ''jmemcached'' from the command line, just run Java against the cli "-with-dependendencies" JAR.

The CLI accepts the following options:

 -b,--binary              binary protocol mode
 -bs,--block-size <arg>   block size (in bytes) for external memory mapped
                          file allocator.  default is 8 bytes
 -c,--ceiling <arg>       ceiling memory to use; in bytes, specify K, kb,
                          M, GB for larger units
 -f,--mapped-file <arg>   use external (from JVM) heap through a memory
                          mapped file
 -h,--help                print this help screen
 -i,--idle <arg>          disconnect after idle <x> seconds
 -l,--listen <arg>        Address to listen on
 -m,--memory <arg>        max memory to use; in bytes, specify K, kb, M,
                          GB for larger units
 -p,--port <arg>          port to listen on
 -s,--size <arg>          max items
 -v                       verbose (show commands)
 -V                       Show version number

How can I get it?

To make use of jmemcached in your project, the easiest way is to use Maven 2. jmemcached artifacts are available in Maven 2 central.

And then add the dependency:

    <dependency>
        <groupId>com.thimbleware.jmemcached</groupId>
        <artifactId>jmemcached-core</artifactId>
        <version>1.0.0</version>
    </dependency>

If you are not using Maven, you can retrieve the compiled JARs directly via HTTP from the Maven 2 central repository at http://repo2.maven.org/maven2/com/thimbleware/jmemcached/

Debian/Ubuntu packages are also available in the repository in the jmemcached-cli

What's next?

Missing features (when compared against the native C version):

delayed 'flush_all'
UDP protocol

Thanks to...

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