[jira] [Created] (BEAM-3039) DatastoreIO.Write fails multiple mutations of same entity

["Alexander Hoem Rosbach (JIRA)" <ji...@apache.org>]

Alexander Hoem Rosbach created BEAM-3039:
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             Summary: DatastoreIO.Write fails multiple mutations of same entity
                 Key: BEAM-3039
                 URL: https://issues.apache.org/jira/browse/BEAM-3039
             Project: Beam
          Issue Type: Bug
          Components: sdk-java-extensions
    Affects Versions: 2.1.0
            Reporter: Alexander Hoem Rosbach
            Assignee: Reuven Lax
            Priority: Minor


When streaming messages from a source that doesn't guarantee once-only-delivery, but has at-least-once-delivery, then the DatastoreIO.Write will throw an exception which leads to Dataflow retrying the same commit multiple times before giving up. This leads to a significant bottleneck in the pipeline, with the end-result that the data is dropped. This should be handled better.

There are a number of ways to fix this. One of them could be to drop any duplicate mutations within one batch. Non-duplicates should also be handled in some way. Perhaps a use NON-TRANSACTIONAL commit, or make sure the mutations are commited in different commits.

{code}
com.google.datastore.v1.client.DatastoreException: A non-transactional commit may not contain multiple mutations affecting the same entity., code=INVALID_ARGUMENT
        com.google.datastore.v1.client.RemoteRpc.makeException(RemoteRpc.java:126)
        com.google.datastore.v1.client.RemoteRpc.makeException(RemoteRpc.java:169)
        com.google.datastore.v1.client.RemoteRpc.call(RemoteRpc.java:89)
        com.google.datastore.v1.client.Datastore.commit(Datastore.java:84)
        org.apache.beam.sdk.io.gcp.datastore.DatastoreV1$DatastoreWriterFn.flushBatch(DatastoreV1.java:1288)
        org.apache.beam.sdk.io.gcp.datastore.DatastoreV1$DatastoreWriterFn.processElement(DatastoreV1.java:1253) 
{code}



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