Github user HeartSaVioR commented on a diff in the pull request:
https://github.com/apache/storm/pull/477#discussion_r26999928
--- Diff: docs/documentation/FAQ.md ---
@@ -62,6 +62,10 @@ You can join streams with join, merge or multiReduce.
At time of writing, you can't emit to multiple output streams from Trident
-- see [STORM-68](https://issues.apache.org/jira/browse/STORM-68)
+### Why am I getting a NotSerializableException/IllegalStateException when
my topology is being started up?
+
+Within the Storm lifecycle, the topology is instantiated and then
serialized to byte format to be stored in ZooKeeper, prior to the topology
being executed. Within this step, if a spout or bolt within the topology has an
initialized unserializable property, serialization will fail. If there is a
need for a field that is unserializable, initialize it within the bolt or
spout's prepare method, which is run after the topology is delivered to the
worker.
--- End diff --
I'm not sure but it may be better to document "serialized fields' values
are reused when workers are relaunched whether live worker modifies it or
not.".
I had this issue earlier, and sure it was by mistake, but it would be hard
to find bug.
Wish to hear everyone's thought.
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