CounterBuffer

Buffered counters for Java

Sometimes is useful to write counters in a database or a storage system. But, what if we need to continuously increment those counters? Maybe it’s slow or a waste of resources.

Here comes the idea to have a buffer of counters with an automatic system to flush the increments when the buffer is too big or time is passed.

Single counters

The basic usage is to have items and for every one of them having a single counter. For example counting names repetitions; every time a name appears we increment hits counter.

---

Here an example on how to write a counterBuffer basic class:

public class CountingNamesCounterBuffer extends CounterBufferSingleDataSource {

    public CountingNamesCounterBuffer(int maxSize, long maxTimeInSeconds, DataSource dataSource) {
        super( maxSize, maxTimeInSeconds, dataSource );
    }

    @Override
    public void flushObj( CounterAbstract item ) throws FlushException {

        try {
            CounterSingle myItem = (CounterSingle) item;

            Statement stat = getConnection().createStatement();
            try{
                stat.execute("insert into names "
                        + "values('" + myItem.getId() + "', " + myItem.getCount() + ") "
                        + "on duplicate key update count=count+" +  myItem.getCount()
                );
            }finally{
                stat.close();
            }
        } catch (SQLException e) {
            throw new FlushException( e );
        }
    }

}

And here how to use it:

VisitsSingleCounterBuffer visitsBuffer = new VisitsSingleCounterBuffer( 10, 120, dataSource );

visitsBuffer.increment( "George" );
visitsBuffer.increment( "Arthur");
visitsBuffer.increment( "George" );

In this example a counterBuffer with a buffer of size 10 is build. Every 120 seconds a flush thread will run.
The third parameter (datasource) is a JdbcConnectionPool, CounterBuffer will get a connection to run the flush and will close is when finished.

---

Multiple counters

Now, a more serious example.
Imagine you need more than a single counter per every item. For example counting per every item: impressions, views and clicks.

VisitsMultiCounterBuffer visitsBuffer = new VisitsMultiCounterBuffer( 5, 1, dataSource );
		
visitsBuffer.increment( "firstItem", "impression", 1 );
visitsBuffer.increment( "firstItem", "impression", 1 );
visitsBuffer.increment( "firstItem", "view", 1 );
visitsBuffer.increment( "firstItem", "impression", 1 );
visitsBuffer.increment( "firstItem", "click", 1 );
visitsBuffer.increment( "secondItem", "impression", 1);
visitsBuffer.increment( "secondItem", "view", 1);
visitsBuffer.increment( "firstItem", "view", 1 );
visitsBuffer.increment( "secondItem", "impression", 1);
		

And here the code for the class to store in DB out counters

public class VisitsMultiCounterBuffer extends CounterBufferMultiDataSource {

	public VisitsMultiCounterBuffer(int maxSize, long maxTimeInSeconds, DataSource dataSource) {
		super( maxSize, maxTimeInSeconds, dataSource );
	}

	@Override
	public void flushObj( CounterAbstract item ) throws FlushException {
		
		try {
			CounterMulti myItem = (CounterMulti) item;
			
			Statement stat = getConnection().createStatement();
			try{
				
				stat.execute("insert into visits_multi " +
						"values('" + myItem.getId() + "', " + 
						myItem.getCount("impression") + ", " + 
						myItem.getCount("view") +", " + 
						myItem.getCount("click") + ") " +
						"on duplicate key update " +
						"impression=impression+" +  myItem.getCount("impression") +
						", view=view+" +  myItem.getCount("view") +
						", click=click+" +  myItem.getCount("click")
						);
			}finally{
				stat.close();
			}
		} catch (SQLException e) {
			throw new FlushException( e );
		}
	}

}