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https://issues.apache.org/jira/browse/CAMEL-21888?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17937633#comment-17937633
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Ben Manes commented on CAMEL-21888:
-----------------------------------
Oh good, I’ll need to look into your approach! I hope your fix nails the
problem.
The design that I use is to record the access into a queue (ring buffer) that
is drained when full using a tryLock. That can guard a normal lru so it just
batches the work under the lock for replay instead of lru lock contention.
It’s surprisingly hard to get whatever scheme to work as desired. Ehcache uses
sampling for their lru and
[busted|https://gist.github.com/ben-manes/6312727adfa2235cb7c5e25cae523ad0] it
up really badly by not understanding how hash tables work.
> High CPU usage at startup due to Deque.size() iteration in SimpleLRUCache
> -------------------------------------------------------------------------
>
> Key: CAMEL-21888
> URL: https://issues.apache.org/jira/browse/CAMEL-21888
> Project: Camel
> Issue Type: Bug
> Components: came-core
> Affects Versions: 4.7.0
> Reporter: Nadina Florea
> Assignee: Nicolas Filotto
> Priority: Major
>
> Hello,
> Starting with *Camel 4.7.0,* a change was introduced in *SimpleLRUCache,*
> where a *Deque* is now used to track *lastChanges.*
> Please see:
> [https://github.com/apache/camel/commit/a7e696927dea30795a49a4c0ac4a36ee700131ff]
> and CAMEL-20850
> This change causes *high CPU usage at startup* when the cache is populated,
> as *Deque.size() iterates over all cache entries.* This results in 100% CPU
> usage, and the *application failed to start.*
> This issue was observed only in production, after migrating to Camel 4.7.0,
> where the cache size is significantly large (1,200,000 entries at that time).
> Current stable version is Camel 4.6.0. The behavior was reproduced with Camel
> 4.10.0 as well.
>
> We are using {*}KafkaIdempotentRepository{*}, which relies on SimpleLRUCache.
> In our app, we expose a metric that contains the size of the cache at a
> certain point.
> {code:java}
> @Bean
> @ConditionalOnBean(KafkaIdempotentRepository.class)
> public MeterBinder cacheSize(final KafkaIdempotentRepository
> idempotentRepository) {
> return registry ->
> Gauge.builder("cacheSize",idempotentRepository::getCacheSize)
> .register(registry);
> }{code}
> Would appreciate any insights on this issue.
>
>
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