[jboss-jira] [JBoss JIRA] Updated: (JBCACHE-658) Fast locking for mostly-read PojoCache

[Ben Wang (JIRA)]

     [ http://jira.jboss.com/jira/browse/JBCACHE-658?page=all ]

Ben Wang updated JBCACHE-658:
-----------------------------

      Component/s: PojoCache
    Fix Version/s: POJOCache

> Fast locking for mostly-read PojoCache
> --------------------------------------
>
>                 Key: JBCACHE-658
>                 URL: http://jira.jboss.com/jira/browse/JBCACHE-658
>             Project: JBoss Cache
>          Issue Type: Feature Request
>      Security Level: Public(Everyone can see) 
>          Components: PojoCache
>            Reporter: Nitzan Niv
>         Assigned To: Ben Wang
>             Fix For: POJOCache
>
>
> The locking mechanism locks all the nodes in the path from the tree root to the modified node. If the cache contains a deep hierarchy of nodes (e.g., PojoCache that contains complex objects) and the usage of the cache
> is mostly-read the locking overhead is unnecessarilly large.
> To enable REPEATABLE_READ isolation level with minimal overhead (but with reduced update parallelism) just the tree root should be locked instead of the nodes-path. To define this policy as a new isloation level ("single"):
> Change in PessimisticLockInterceptor (line 199):
>          else {
>              if(isolation_level == IsolationLevel.SINGLE)  {//XXX
>                  if (i == 0) {
>                      acquired=child_node.acquire(owner, lock_timeout, lock_type);
>                  }
>              } else {
>             if(lock_type == DataNode.LOCK_TYPE_WRITE && i == (treeNodeSize - 1)) {
>                acquired=child_node.acquire(owner, lock_timeout, DataNode.LOCK_TYPE_WRITE);
>             }
>             else {
>                acquired=child_node.acquire(owner, lock_timeout, DataNode.LOCK_TYPE_READ);
>             }
>              }//XXX
>          }
> in LockStrategyFactory.java:
>       if (lockingLevel == IsolationLevel.REPEATABLE_READ || lockingLevel == IsolationLevel.SINGLE) //XXX
>          return new LockStrategyRepeatableRead();
> and add the "SINGLE" isolation level to IsolationLevel.java.

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