[BEAM-14023] Slowly updating global window side inputs example reads singleton side input with multiple elements per window

• Type: Bug
• Status: Open
• Priority: P2
• Resolution: Unresolved
• Component/s: examples-java, sdk-java-core
• Assignee: Unassigned
• Reporter: John Gerassimou
• Created: 01/Mar/22 22:51
• Updated: 04/Jun/22 23:22

Description

The example "The Slowly updating global window side inputs" [1] produces an unexpected error. Our implementation follows the example but uses a 30-second duration. The error first occurred after 4000 triggers. The pipeline ran on Dataflow using Java 1.8 and Beam SDK 2.33.0.

 

Caused by: org.apache.beam.vendor.guava.v26_0_jre.com.google.common.util.concurrent.UncheckedExecutionException: java.lang.IllegalArgumentException: PCollection with more than one element accessed as a singleton view. 

 

 

Applying a combine function before applying the view singleton has no positive effect. Changing the refresh duration to 5 minutes alleviates or delays the error. 

Relevant post:

• https://lists.apache.org/thread/v005b7osqxv774wjpjhg103bqto4v7yh
• https://lists.apache.org/thread/wfm77wkqrkwlrhgbnq9f3x8nyzsn51xm
• https://github.com/spotify/scio/issues/1190
• https://github.com/spotify/scio/issues/3521

Please let me know if you have any questions.

References:

 [1] https://beam.apache.org/documentation/patterns/side-inputs/