Question

I have a CXF-based web service with a one-way method say:
Service.report()

While a report() from a client is being processed, I want to make another incoming report() from the same client IP wait till the first request is processed. Seen from a client, report() is an atomic operation and successive calls to report() should be processed sequentially.

How can I best implement this locking mechanism? Will I need to implement a per-client queue or is there a simple way to accomplish this?

Answer 1

You don’t need a full blown queue for this. A simple object synchronisation should work

static ConcurrentMap syncMap = new ConcurrentHashMap();

public void report()
{
   String clientIp =  ...
   syncMap.putIfAbsent(clientIp, new Object()); // just new Object is good enough to sync on
   synchronized(syncMap.get(clientIp))
   {
      //do synchronized stuff.
   }
}