Under high load when the timing is just right our camel routes are getting ConcurrentModificationExceptions. We have tracked this down to NormalizedMessageImpl.java in servicemix-core. Specifically in the createPropertiesMap method on line 295. There's a comment that Normalized exchanges do not need to be thread-safe but we are definitely seeing issues with this. We changed the use of HashMap to ConcurrentHashMap and do not see the problem anymore.
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