[NIFI-989] Support size() operation in distributed map cache server

• Type: Improvement
• Status: Open
• Priority: Minor
• Resolution: Unresolved
• Component/s: Core Framework
• Labels: cache command-line distributed improvement
• Assignee: Unassigned
• Reporter: Joe Mészáros
• Created: 23/Sep/15 15:23
• Updated: 29/Mar/22 22:24

Description

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.