How to solve the problem of storm trident distributed query

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The background is a simple scenario where sentences are read from a document, and then the number of times each word appears is calculated, and the results are stored in MyMemoryMapState.

Then do a distributed query:

Topology.newDRPCStream ("word", drpc) / / the default input fields is "args" .stateQuery (wordCounts, new Fields ("args"), new MapGet (), new Fields ("count"))

Code for drpc invocation

Drpc.execute ("word", "first")

The result shows that sometimes the query is null, sometimes there is data. It's strange that since you already have data in memory, why can't you find it?

Later I tried to modify the distributed query code.

The default input fields for topology.newDRPCStream ("word", drpc) / / is "args" .groupBy (new Fields ("args")) .stateQuery (wordCounts, new Fields ("args"), new MapGet (), new Fields ("count"))

And then the results can be queried every time. I don't understand why we have to groupby. Need to know the process of stateQuery!

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