Kalithas Sendrayan created CAMEL-24321:
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Summary: Stream caching: allow the spool directory to be resolved
per-Exchange
Key: CAMEL-24321
URL: https://issues.apache.org/jira/browse/CAMEL-24321
Project: Camel
Issue Type: Improvement
Components: came-core
Affects Versions: 4.14.2
Reporter: Kalithas Sendrayan
h3. Use case
Multi-route runtimes need each route's spilled bytes to go to a caller-decided
directory. For example:
* We need each route's spool data isolated (route A's payloads must not share
a directory with route B's)
* We need to monitor spool directory usage at the route level
h3. Current behavior
Stream caching is scoped per CamelContext: the spool directory is resolved once
at startup (DefaultStreamCachingStrategy.doStart() via TempDirHelper) into a
single directory. Every route that spills to disk uses that one context-wide
directory.
h3. Limitation
The Exchange is available where CachedOutputStream is constructed (and it
carries
the route id via getFromRouteId()), but it is dropped before the directory is
chosen.
FileInputStreamCache.TempFileManager.createOutputStream(StreamCachingStrategy)
resolves the location from the no-arg strategy.getSpoolDirectory() and never
sees
the Exchange:
{code:java}
tempFile = FileUtil.createTempFile("cos", ".tmp", strategy.getSpoolDirectory());
{code}
So even a custom StreamCachingStrategy cannot make a per-route decision - the
information it needs - the Exchange, from which the route id is available - is
not passed to the point where the directory is selected.
h3. Expected capability
A way to choose the spool directory per route (per Exchange), so a custom
StreamCachingStrategy can direct each route's spilled bytes to its own
directory.
h3. Steps to reproduce
# Configure stream caching with spooling enabled (low spool threshold).
# Deploy two routes intended to spill into different directories.
# Send a large body (over the threshold) to each so both spill to disk.
# Both temp files land in the same context-wide spool directory - there is no
API to make them differ per route.
h3. Environment / version
Reproduced on Apache Camel 4.14.2. The stream-cache classes are in camel-support
(CachedOutputStream, FileInputStreamCache); the strategy is in camel-base-engine
(DefaultStreamCachingStrategy).
h3. Relevant implementation references
* org.apache.camel.converter.stream.CachedOutputStream (camel-support)
* org.apache.camel.converter.stream.FileInputStreamCache (camel-support; inner
TempFileManager)
* org.apache.camel.impl.engine.DefaultStreamCachingStrategy
(camel-base-engine; doStart via TempDirHelper)
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