[Feature Request]: Add soft-deadline before 1 minute hard-deadline to Spanner Change Stream IO connector

[dedocibula]

Currently, Spanner Change Stream IO connector expects the beam framework to issue a split event either 5s or every 5MB of processed payload. In case that such event doesn't occur processing will continue until ultimately 1m pre-set timeout for Change Stream query is reached. This will cause the existing work to be dropped and query to be rescheduled. This feature tracks work for adding a soft deadline before the hard deadline that will allow to commit already processed work and updates internal processing low watermark

Issue Priority

Priority: 2 (default / most feature requests should be filed as P2)

Issue Components

• Component: Python SDK
• Component: Java SDK
• Component: Go SDK
• Component: Typescript SDK
• Component: IO connector
• Component: Beam YAML
• Component: Beam examples
• Component: Beam playground
• Component: Beam katas
• Component: Website
• Component: Infrastructure
• Component: Spark Runner
• Component: Flink Runner
• Component: Samza Runner
• Component: Twister2 Runner
• Component: Hazelcast Jet Runner
• Component: Google Cloud Dataflow Runner

[dedocibula]

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