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From "Mark Payne (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (NIFI-989) Support size() operation in distributed map cache
Date Wed, 23 Sep 2015 18:20:04 GMT

    [ https://issues.apache.org/jira/browse/NIFI-989?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14904968#comment-14904968
] 

Mark Payne commented on NIFI-989:
---------------------------------

[~joemeszaros] - one thing to note here is that the DistributedMapCacheClient is an interface
that exists in the services-api nar. This means that there can be many different implementations
of the interface. I know others do exist, outside of apache nifi. As a result, we can't really
change the API of that service in a non-backward-compatible way. I.e., we can't add new methods
to that interface. At least, not until version 1.0.0.

One way to address this is to provide a new interface, SizableDistributedMapCacheClient that
extends DistributedMapCacheClient, and then add the size() method there. Then any processor
or extension point that wants to use the size() method would rely on this SizableDistributedMapCacheClient.

Thanks
-Mark

> Support size() operation in distributed map cache
> -------------------------------------------------
>
>                 Key: NIFI-989
>                 URL: https://issues.apache.org/jira/browse/NIFI-989
>             Project: Apache NiFi
>          Issue Type: Improvement
>          Components: Core Framework
>            Reporter: Joe Mészáros
>            Priority: Minor
>              Labels: cache, command-line, distributed, improvement
>
> The distributed map cache server is a great tool for caching along with the cache client
(DistributedMapCacheClientService), but after you configure and enable it, it is a black box.
You are unable to get any information from the cache e.g how much entries live in the cache.
> The purpose of this issue to extend the cache interface and associated implementations
to support the size() operation, which returns the number of 
> entries in the distributed cache. 
> It could be a first step in a direction of a more transparent cache, where the user can
understand, what happens with the distributed cache. I mean after the size() operation, it
could be really helpful to implement a stats() command, which s used to query the server about
statistics it
> maintains and other internal data (e.g. evictions, hit rates, ...). 
> Similar to:
>  - memcached : https://docs.oracle.com/cd/E17952_01/refman-5.0-en/ha-memcached-stats-general.html
> - couchbase: http://blog.couchbase.com/monitoring-couchbase-cluster
> - redis: http://haydenjames.io/using-redis-stat-for-redis-statistics-tracking/
> I implemented a really simple command line tool, which can interact with the cache server
from the command line, e.g. get a cache entry and it also able to get the size of the cache,
which could be useful, when you would like to debug cache related problems, or just get basic
interaction with the cache.



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