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https://issues.apache.org/jira/browse/SOLR-15859?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17651088#comment-17651088
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Shawn Heisey commented on SOLR-15859:
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{quote}I think it might be possible (and preferable?) to implement this as a
custom {{SolrCache<K, V>}} implementation that wraps {{{}solr.CaffeineCache<K,
MetadataWrapper<V>>{}}}. I think [~ben.manes] was alluding to something like
this "MetadataWrapper" approach in his comment above.
{quote}
I have no idea how to go from those statements to actual usable code. And I
don't want to ask you to write it for me, I'd like to do that myself. But if
you can come up with back-of-the-envelope pseudocode very quickly that I can
flesh out into actual code, that would be appreciated.
If what you're describing would involve changes to the way that specific caches
(like filterCache) get implemented, then I'm REALLY going to be out of my
depth. I once tried to look at that and got completely lost trying to follow
the code. In much the same way as what happened when I tried to understand
SolrCloud cluster management with the overseer.
> Add handler to dump filter cache
> --------------------------------
>
> Key: SOLR-15859
> URL: https://issues.apache.org/jira/browse/SOLR-15859
> Project: Solr
> Issue Type: Improvement
> Reporter: Andy Lester
> Assignee: Shawn Heisey
> Priority: Major
> Labels: FQ, cache, filtercache, metrics
> Attachments: cacheinfo-1.patch, cacheinfo-2.patch, cacheinfo.patch,
> fix_92_startup.patch
>
>
> It would be very helpful to be able to inspect the contents of the
> filterCache.
> I'd like to be able to query something like
> {{/admin/caches?type=filter&nentries=1000&sort=numHits+DESC}}
> nentries would be allowed to be -1 to get everything.
> It would be nice to see these data items for each entry. I don't know which
> are available, but I'm thinking blue sky here:
> * cache key, exactly as stored
> * Timestamp when the entry was inserted
> * Whether the insertion of the entry evicted another entry, and if so which
> one
> * Timestamp of when this entry was last hit
> * Number of hits on this entry forever
> * Number of hits on this entry over some time period
> * Number of documents matched by the filter
> * Number of bytes of memory used by the filter
> These are the sorts of questions I'd like to be able answer:
> * "I just did a query that I expect will have added a cache entry. Did it?"
> * "Are my queries hitting existing cache entries?"
> * "How big should I set my filterCache size? Should I limit it by number of
> entries or RAM usage?"
> * "Which of my FQs are getting used the most? These are the ones I want in
> my firstSearcher queries." (I currently determine this by processing my old
> solr logs)
> * "Which filters give me the most bang for the buck in terms of RAM usage?"
> * "I have filter X and filter Y, but would it be beneficial if I made a
> filter X AND Y?"
> * "Which FQs are used more at certain times of the day? (Assuming I take
> regular snapshots throughout the day)"
> I imagine a response might look like:
> {{{}}
> {{ "responseHeader": {}}
> {{ "status": 0,}}
> {{ "QTime": 961}}
> {{ },}}
> {{ "response": {}}
> {{ "numFound": 12104,}}
> {{ "filterCacheKeys": {}}
> {{ [}}
> {{ "language:eng": {}}
> {{ "inserted": "2021-12-04T07:34:16Z",}}
> {{ "lastHit": "2021-12-04T18:17:43Z",}}
> {{ "numHits": 15065,}}
> {{ "numHitsInPastHour": 2319,}}
> {{ "evictedKey": "agelevel:4 shippable:Y",}}
> {{ "numRecordsMatchedByFilter": 24328753,}}
> {{ "bytesUsed": 3041094}}
> {{ }}}
> {{ ],}}
> {{ [}}
> {{ "is_set:N": {}}
> {{ ...}}
> {{ }}}
> {{ ],}}
> {{ [}}
> {{ "language:spa": {}}
> {{ ...}}
> {{ }}}
> {{ ]}}
> {{ }}}
> {{}}}
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