AsyncCacheLoader

[karnivas]

I want to use jdbc writes in async mode. I've tailored MyAsyncCacheLoader extending AsyncCacheLoader with overridden put methods. I'm calling super(new JDBCCacheLoader) in the constructor and loading the config file. Unexpectedly my properties file alone gets loaded, but doesn't call my put method which i've overrided, instead it writes to the DB directly. Please suggest me how to proceed. Alternate solutions are welcomed.

My Code goes as

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.Iterator;
import java.util.Map;
import java.util.Properties;
import java.util.Set;

import org.jboss.cache.DataNode;
import org.jboss.cache.Fqn;
import org.jboss.cache.PropertyConfigurator;
import org.jboss.cache.TreeCache;
import org.jboss.cache.loader.AsyncCacheLoader;
import org.jboss.cache.loader.AsyncExtendedCacheLoader;
import org.jboss.cache.loader.ExtendedCacheLoader;
import org.jboss.cache.loader.FileCacheLoader;
import org.jboss.cache.loader.JDBCCacheLoader;
import org.jboss.cache.loader.JDBCExtendedCacheLoader;


public class MyAsyncCacheLoader extends AsyncCacheLoader {
private static long timeStamp;
private static long oneHrtimeStamp;

public MyAsyncCacheLoader(){
super(new JDBCCacheLoader());

Properties cfg = new Properties();
try {
cfg.load(new FileInputStream(new File("async.properties")));
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
System.out.println("Read the value : " + cfg);
String key = "cache.async.batchSize";
String val = cfg.getProperty (key) ;
System.out.println("Read the value : " + val);
this.setConfig(cfg);
timeStamp=0;
oneHrtimeStamp=0;
}
public Object put(Fqn name, Object key, Object value) throws Exception{
System.out.println("Inside MyAsyncCacheLoader put....");
if(!name.getLast().equals("operation"))
{
System.out.println(name.toString()+ " written to DB");
super.put(name, key, value);
}
else
System.out.println(name.toString()+ " will not be written to DB");

return value;

}

public void put(Fqn name, Map attributes) throws Exception
{
System.out.println("Inside MyAsyncCacheLoader Put (map) method :: Fqn = "+ name );
if(!name.getLast().equals("operation"))
{
System.out.println(name.toString()+ " written to DB");

super.put(name, attributes);
}
else
System.out.println(name.toString()+ " will not be written to DB");


}
}

[manik]

?!?? If you want to use a JDBC cache loader in Async mode just set async to true in the Cache Loader config.

Internally, we will wrap the JDBCCacheLoader with an AsyncCacheLoader if async is true, but this is transparent to you.

See section 7.2 in:

http://labs.jboss.com/file-access/default/members/jbosscache/freezone/docs/1.4.1.SP2/TreeCache/en/html/cache_loaders.html

[karnivas]

Thanks for the reply !!

If i'm setting async to true, does the db writes happen in a separate thread. In that case can i control the no. of DB writes in a specific time ? eg: Can i write 1000 requests in 1 min ?

[karnivas]

Adding to the above, can i make the cache store data into the persistent store or DB every 1 minute irrespective of the no. operations performed on the cache.

Further, irrespective of any operations done on the cache, how can i schedule the cache loader to persist cache data every 1 min.

If this isn't possible how else can i configure the async behaviour ? Is there a configuration file ?

[genman]

Take a look at the Javadoc:

http://labs.jboss.com/file-access/default/members/jbosscache/freezone/docs/1.4.1.SP2/api/org/jboss/cache/loader/AsyncCacheLoader.html

If you want a flush every minute, and no more, then set batchSize to a very high value, then pollWait to one minute (in milliseconds.)

My recommendation would be to flush every 1-5 seconds at most, and set the batch size to a reasonable value (such as 100). This is so that one DB operation is not too long.

[karnivas]

Thanks Again !!

I need to schedule the cacheloader to persist DB for a specific node alone in the cache data every 1 min. Can i achieve and configure this ?

I've tried with batchSize and pollWait but unsuccessful, so let me know how can i achieve this. An example will be more sufficient. Thanks in advance.

[genman]

What did you try and what did you see and how did it not match your expectations?

I'm not sure the Async cache loader is going to be what you want if you want to persist a single node every minute. Perhaps you should use a timer and "evict" call instead.