ben-manes commented on a change in pull request #580:
URL: https://github.com/apache/solr/pull/580#discussion_r797143819
##########
File path:
solr/core/src/java/org/apache/solr/core/TransientSolrCoreCacheDefault.java
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@@ -89,6 +86,21 @@ public TransientSolrCoreCacheDefault(CoreContainer
coreContainer) {
transientDescriptors = new LinkedHashMap<>(initialCapacity);
}
+ private void onEvict(SolrCore core) {
+ if (core.getOpenCount() > 1) {
Review comment:
The way to handle this is to [pin
entries](https://github.com/ben-manes/caffeine/wiki/Faq#pinning-entries). When
an entry should be pinned you can update it through the cache (e.g.
`cache.asMap.compute`) and have a `Weigher` to evaluate the entry's size as
`0`. Then it won't take any capacity and be skipped over during size eviction.
Similarly for expiration using an `Expiry` that gives an infinite lifetime.
This approach is preferred because then the cache won't surprisingly violate
the contracts, won't perform O(n) scans searching for candidates, and the
decisions are more explicit. Caffeine skips over zero-weight entries, but in
the future it could move them elsewhere. So far this pin/unpin approach seems
to clearer than Ehcache's
[EvictionAdvisor](https://github.com/ehcache/ehcache3/blob/master/ehcache-api/src/main/java/org/ehcache/config/EvictionAdvisor.java)
(a soft no; will evict an entry
[regardless](https://github.com/ehcache/ehcache3/blob/5cfa96b868423f0fbb19bf27ead647823b14a165/ehcache-impl/src/main/java/org/ehcache/impl/internal/store/heap/OnHeapStore.java#L1578-L1583)
of the advice) and Coherence's
[EvictionApprover](https://github.com/oracle/coherence/blob/d97c16ca8069143a8117356914da1bc341e8c19f/prj/coherence-core/src/main/java/com/tangosol/net/cache/ConfigurableCacheMap.java#L331-L364)
is a hard no (which could lead to heap exhaustion), but please let me know if
you ru
n into issues that advocate for reevaluating our approach.
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