Error (sometimes) occurs while deserializing the session.notes

[rik-overvelde]

Hello,

I'm trying to get Hazelcast session replication up and running for an existing application running under tomcat9. I'm using the hazelcast-tomcat9-sessionmanager, with sticky="false".
However, I sometimes get an issue where a session can no longer be deserialized because of the ofllowing error:
com.hazelcast.nio.serialization.HazelcastSerializationException: Problem while reading DataSerializable, namespace: 0, ID: 0, class: 'com.hazelcast.session.HazelcastSession', exception: Illegal initial capacity: -2147483648

Some debugging has made me come to the conclusion that the problem lies with the session.notes map (Originally a hashtable). When deserializing the map, it find a mapSize (or initial load) of '1886388339'. When initializing the hashmap, Java uses the following calculation to determine the initial map size : (initialLoad / 0.75) + 1. The +1 leads to an overflow, so that it tries to initialize the map with a negative value.

Sadly, I haven't found out yet what happens that causes the session to get serialized with this map size. This seems rather random right now. A workaround might be to limit the mapSize to a max value of '1886388338' so that the map will always be initialized with the right value.