[infinispan-issues] [JBoss JIRA] (ISPN-2916) Group-based expiration

[Dan Berindei (JIRA)]

    [ https://issues.jboss.org/browse/ISPN-2916?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12958662#comment-12958662 ] 

Dan Berindei commented on ISPN-2916:
------------------------------------

Indeed [~pferraro], that was the solution I was going to suggest as well.

OTOH Radim is also right, there are two problems:
1. Expiration doesn't actually remove the entry, so it's possible for an entry to re-appear in the cache if the timer is not monotonic. In particular, it's very likely that the key does not expire at the exact same time on all the nodes, so a node that doesn't have the group locally may get different results depending on which owner answers first (since we send the remote get to all the owners). True, this won't happen very often, but it can certainly happen during state transfer.
2. Reading doesn't acquire any locks. So just because you read the a key in a transaction, it doesn't mean that the key can't expire while the transaction is active. Note that expiration doesn't acquire any locks either, but that might need to change in order to implement expiration listeners.

                
> Group-based expiration
> ----------------------
>
>                 Key: ISPN-2916
>                 URL: https://issues.jboss.org/browse/ISPN-2916
>             Project: Infinispan
>          Issue Type: Feature Request
>          Components: Core
>    Affects Versions: 5.2.5.Final
>            Reporter: Paul Ferraro
>            Assignee: Mircea Markus
>
> Now that WildFly represents a web session as a group of cache entries (instead of a single entry containing an atomic map), there are a few hurdles preventing us from leveraging infinispan-managed expiration.
> One of which is the fact that expiration of cache entries within a group *must* be atomic.  It would be very bad if a request arrives for a session whose entries are in the process of being expired.  The expiration thread should obtain a lock on *all* the keys for a group (or at least some pre-determined "primary" key), so that late session access doesn't result in session attributes mysteriously disappearing (because they were independently expired).  This can also cause integrity constraint violations if cache entries reference other entries in the group.  e.g. currently the "primary" cache entry for a session (keyed by session id), contains a set of attribute names.  These names correspond to other cache entries that contain the value of a given attribute for that session.

--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators
For more information on JIRA, see: http://www.atlassian.com/software/jira