[infinispan-issues] [JBoss JIRA] (ISPN-694) Create expiration notification for in-memory cache entries

[Dan Berindei (JIRA)]

    [ https://issues.jboss.org/browse/ISPN-694?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12959593#comment-12959593 ] 

Dan Berindei commented on ISPN-694:
-----------------------------------

[~william.burns] right, I was thinking that without key affinity the requests will go to random nodes, so the chance of hitting either owner is the same. But I guess if {{maxIdle}} is on the same scale as the average access interval, it's still possible to get a big difference in expiration times.

I do think that, for most of the users, using {{maxIdle}} and {{lifespan}} implies that a {{null}} value is always correct: should the user disable caching altogether, the application should still work. So I don't see the fact that an entry expires on different nodes at different times as a consistency problem, it's just that the user must have another source for the data in the cache.

In fact, I'm not sure what a {{maxIdle}} expiration listener could do. It can't invalidate the values on the other owners, because it might actually be used there. It shouldn't reload the entry from the canonical source, like a {{lifespan}} expiration listener might do, because the notification itself tells it the entry isn't needed. So I wonder if we shouldn't design the expiration listeners to not fire on {{maxIdle}} expiration.

For web server sessions as well, I think they need to be updated on each request with the last access time, so they could use {{lifespan}} instead of {{maxIdle}} for a sentinel entry and no expiration for the rest of the entries.
                
> Create expiration notification for in-memory cache entries
> ----------------------------------------------------------
>
>                 Key: ISPN-694
>                 URL: https://issues.jboss.org/browse/ISPN-694
>             Project: Infinispan
>          Issue Type: Feature Request
>          Components: Eviction
>         Environment: any
>            Reporter: Edouard Boily
>            Assignee: Galder Zamarreño
>         Attachments: 01.patch
>
>
> Create a CacheEntryExpired notification and make EvictionManager send this notification when a cache entry is evicted because it is expired.
> Also mage sure the cache entry value is sent over in the event.
> CacheEntryEvicted notification should also send the entry value in the event.

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