Details
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Type:
Bug
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Status: Resolved
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Priority:
Major
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Resolution: Fixed
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Affects Version/s: 2.16.3, 2.17.3
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Fix Version/s: 2.19.0
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Component/s: camel-core
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Labels:None
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Environment:
MacOS 10.11.6, JRE 1.7.0_79
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Estimated Complexity:Advanced
Description
Problem
The oldExchange is null more than once in the aggregator if a recipient list is processed in parallel.
Camel route
In my Camel route, a recipient list is worked of in parallel:
from("direct:start") .to("direct:pre") .recipientList().method(new MyRecipientListBuilder()) .stopOnException() .aggregationStrategy(new MyAggregationStrategy()) .parallelProcessing() .end() .bean(new MyPostProcessor());
Snippet of MyAggregationStrategy:
@Override @SuppressWarnings("unchecked") public Exchange aggregate(final Exchange oldExchange, final Exchange newExchange) { if (oldExchange == null) { // this is the case more than once which is not expected! } // ...
oldExchange is null more than once which is not expected and which contradicts the contract with Camel.
Analysis
Unfortunately, I am not able to provide a (simple) unit test for comprehending the problem. Furthermore our (complex) unit tests are not deterministic due to the root cause of the problem.
During the processing, Camel invokes ParallelAggregateTask.doAggregateInternal(). If aggregation is not done in parallel (as it is the case in our route), this is supposed to be done synchronously:
protected void doAggregateInternal(AggregationStrategy strategy, AtomicExchange result, Exchange exchange) { if (strategy != null) { // prepare the exchanges for aggregation Exchange oldExchange = result.get(); ExchangeHelper.prepareAggregation(oldExchange, exchange); result.set(strategy.aggregate(oldExchange, exchange)); } }
However, is it possible that we face a race condition in doAggregateInternal even if this method is supposed to be invoked synchronously?
