Github user justinleet commented on the issue: https://github.com/apache/metron/pull/970 @merrimanr I fixed the metaalert template; I'd forgotten to update the original placeholder one in addition to the test one. I haven't had a chance to run it up and see if it fixes what you saw, but it explains the _childDocuments_ problem. The message itself is a bit of a red herring: it's a special field, so the lack of definition at all caused problem.
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