New Open Source Cache System

>Does it implement the same built-in memory clustering mechanism as it can be seen in Terracotta?

As I understand it, Terracotta does something under the hood of the JVM so that the Java code transparently sees objects from other VMs. sccache does not work this way. It treats the external cache servers as a type of HashMap and writes/reads objects based on the hash of the object's key. I believe memcached, Coherence and JCS work this way as well.

The post contains both "is non-transactional" and "Extremely fast - >20K transactions a minute (depending on hardware)" ... I assume the latter to be an atomic write action to cache, or is it something different?

Yes, I'll correct that. I was using "transactional" with different meanings.

>exactly which parts of shop.com is this cache being used for? 

We cache generated HTML pages, SQL queries, HTTP Sessions, POJO objects, etc.

[quote=tech0513]How do you overcome file fragmentation after repeated record deletions? [/quote]

sccache uses a data store I wrote (called CCDB2). It's actually usable by itself if anyone's interested. It re-uses blocks if size allows it to. But, in general, fragmentation isn't an issue. Here's the alogrithm:

A maximum TTL must be chosen - at SHOP.COM we use 12 hours. Every max/2 hours, the current datafile is closed for new objects and a new datafile is created. After max + max/2 hours, you will have 3 datafiles. At max * 2 hours, the third datafile is guaranteed to have nothing but stale objects and is deleted.

Created a quick test:

public class TestServer {

    public static void main(String[] args) throws Exception {
        SCServerFactory factory = ShopComCacheFactory.getServerFactory();
        SCServerContext context = factory.newContext();
        context.port(1111);
        SCStorage db = CCDB2StorageFactory.create(new CCDB2Parameters());
        db.open(new File("."));
        SCServer server = factory.newServer(context, db);
        server.join();
    }

}

public class ClientWTest {

    public static void main(String[] args) throws Exception {
        SCCache myCache = getCache();
        int max = 100;
        for (int i = 0; i < max; i++) {
            Person person = new Person(getName(i));
            SCDataBlock block = new SCDataBlock(person.getName(), person);
            block.canBeStoredInMemory(false);
            block.canBeStoredExternally(true);
            myCache.put(block);
        }
    }

    static SCCache getCache() throws Exception {
        SCClientFactory clientFactory = ShopComCacheFactory.getClientFactory();
        SCClientContext context = clientFactory.newContext();
        context.address(new InetSocketAddress("localhost", 1111));
        SCClientManager manager = clientFactory.newClientManager(context);
        return new SCCache(manager);
    }

    static String getName(int i) {
        return "person" + i;
    }
} 

public class ClientRTest {

    public static void main(String[] args) throws Exception {
        SCCache myCache = ClientWTest.getCache();

        for (int i = 0; i < 20; i++) {
            SCDataBlock block = new SCDataBlock(ClientWTest.getName(i));
            block.canBeStoredInMemory(false);
            block.canBeStoredExternally(true);
            Object value = myCache.get(block);
            System.out.println("value [" + i + "] = " + value);
        }
    }
}
 

After that:

1. start the server

2. run ClientWTest

3. run ClientRTest - no results returned. Any ideas why? If it's of any help - only data file ccdb23747138201158134.db was created - no index file.

Thanks

A new patch is available:

http://code.google.com/p/sccache/