JBoss Community Archive (Read Only)

Infinispan 5.0

Invocation Flags

A very important aspect of getting the most of Infinispan data grids is the use of per-invocation flags in order to provide specific behaivour to each particular cache call. By doing this, some very important optimizations can be implemented potentially saving precious time. One of the most popular usages of flags can be found right in Cache API, underneath the putForExternalRead() method which is used to load an Infinispan cache with data read from an external resource. In order to make this call efficient, Infinispan basically calls a normal put operation passing the following flags: FAIL_SILENTLY, FORCE_ASYNCHRONOUS, ZERO_LOCK_ACQUISITION_TIMEOUT

What Infinispan is doing here is effectively saying that when putting data read from external read, it will use an almost-zero lock aquisition time and that if the locks cannot be acquired, it will fail silently without throwing any exception related to lock acquisition. It also specifies that regardless of the cache mode, if the cache is clustered, it will replicate asynchronously and so won't wait for responses from other nodes. The combination of all these flags make this kind of operation very efficient, and the efficiency comes from the fact this type of putForExternalRead calls are used with the knowledge that client can always head back to a persistent store of some sorts to retrieve the data that should be stored in memory. So, any attempt to store the data is just a best effort and if not possible, the client should try again if there's a cache miss.

If you want to use these or any other flags available, which by the way are described in detail the Flag enumeration, you simply need to get hold of the advanced cache and add the flags you need via the withFlags() method call. For example:

Cache cache = ...
   .put("local", "only"); 

It's worth noting that these flags are only active for the duration of the cache operation. If the same flags need to be used in several invocations, even if they're in the same transaction, withFlags() needs to be called repeatedly. Clearly, if the cache operation is to be replicated in another node, the flags are carried over to the remote nodes as well.

Another very important use case is when you want a write operation such as put() to not return the previous value. To do that, you need to use two flags to make sure that in a distributed environment, no remote lookup is done to potentially get previous value, and if the cache is configured with a cache loader, to avoid loading the previous value from the cache store. You can see these two flags in action in the following example:

Cache cache = ...
   .put("local", "only")

For more information, please check the Flag enumeration javadoc.

JBoss.org Content Archive (Read Only), exported from JBoss Community Documentation Editor at 2020-03-11 09:08:36 UTC, last content change 2011-07-20 09:57:21 UTC.