Details
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Bug
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Status: Resolved
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Major
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Resolution: Fixed
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3.10.0, 4.6.0
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None
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Unknown
Description
Out Of Memory (OOM) occurs when using the Recipient List with a large number of dynamic URLs. For example:
.recipientList(simple("http://downstream-server/employee/${header.emplId}"))
with a large number of values for ${header.emplId} leads to the OOM.
REPRODUCER:
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https://github.com/artnaseef/camel-recipient-list-oom-reproducer
See the README.md for instructions to reproduce and detect the problem
DETAILS
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The MulticastProcessor, which RecipientListProcessor extends, has the following "unlimited" cache:
private final ConcurrentMap<Processor, Processor> errorHandlers = new ConcurrentHashMap<>();
Entries are added to this map for every unique processor created - every unique URL generates a unique processor. The entries themselves are wrapped processor instances for error handling IIUC (to support the custom error handling used by multicast and recipient-list). Entries are only removed from this map on shutdown. Ironically, there is an LRUCache for the processors themselves, with a default maximum size of 1000, so the wrapped processors may get recreated even though the error handler remains in the map indefinitely.
IMPACT VERSIONS:
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Appears to impact versions >= 3.10.0
COMMIT: 0d9227ff16fb00e047fdd087740c87cce01bb545
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It appears this commit introduced the use of the errorHandlers "unlimited" cache for recipient lists.
FOLLOW-UP
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I have ideas and questions for implemeting a fix:
- IDEA 1: We can use an LRUCache for this data structure as well.
- Does it make more sense to remove the entries from errorHandlers when the related Processor entry is removed from it's LRUCache?
- IDEA 2: setting on recipient list to disable the errorHandler cache (for dyamic urls with little chance of duplicates, this could be the best)
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