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Posted to github@beam.apache.org by "raishakti-1983 (via GitHub)" <gi...@apache.org> on 2026/02/20 20:49:50 UTC
[I] [Bug]: Behavior change between Beam 2.66 and 2.71 causing severe buffering [beam]
raishakti-1983 opened a new issue, #37664:
URL: https://github.com/apache/beam/issues/37664
### What happened?
**Environment:**
Beam SDK: 2.66.0 (stable) vs 2.71.0 (problematic)
Runner: Google Cloud Dataflow (Streaming)
Language: Java
Source: KafkaIO
**Pipeline Structure**
KafkaIO
→ MapElements (KafkaRecordToKV)
→ Window.into(...)
→ GroupByKey
→ Sort
→ BigtableIO read/ write
→ Write to Kafka
**Window / Trigger configuration**
window
.triggering(
AfterWatermark.pastEndOfWindow()
.withEarlyFirings(
AfterPane.elementCountAtLeast(elementCount))
.withLateFirings(
AfterPane.elementCountAtLeast(lateElementCount)))
.discardingFiredPanes()
.withAllowedLateness(Duration.standardSeconds(allowedLateness));
window duration: 1 sec
allowed lateness: 600 sec
early count: 100
late count: 1
**Observed behavior**
**Beam 2.66**
Stable message delay, not a big accumulation at GroupAndSort step. Data Freshness graph shows a stable pattern
**Beam 2.71**
Delay shows saw-tooth pattern (buffer → flush cycles). Seems accumulate significantly larger panes before flushing
**Important observation**
No code or traffic change — only Beam version upgrade.
<img width="1795" height="532" alt="Image" src="https://github.com/user-attachments/assets/1457d3ba-5bc4-4407-a702-642ba9f8298c" />
<img width="1839" height="671" alt="Image" src="https://github.com/user-attachments/assets/488b2e7c-af00-422a-aaf3-e2fc98776e25" />
### Issue Priority
Priority: 2 (default / most bugs should be filed as P2)
### Issue Components
- [ ] Component: Python SDK
- [x] 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
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Re: [I] [Bug]: Behavior change between Beam 2.66 and 2.71 causing severe buffering [beam]
Posted by "raishakti-1983 (via GitHub)" <gi...@apache.org>.
raishakti-1983 commented on issue #37664:
URL: https://github.com/apache/beam/issues/37664#issuecomment-3937104530
<img width="1814" height="672" alt="Image" src="https://github.com/user-attachments/assets/dacfe3bd-27ac-4435-854e-617edb27efbb" />
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Re: [I] [Bug]: Behavior change between Beam 2.66 and 2.71 causing severe buffering [beam]
Posted by "github-actions[bot] (via GitHub)" <gi...@apache.org>.
github-actions[bot] commented on issue #37664:
URL: https://github.com/apache/beam/issues/37664#issuecomment-5078542666
This issue has been marked as stale due to 150 days of inactivity. It will be closed in 30 days if no further activity occurs. If you think that’s incorrect or this issue still needs to be addressed, please simply write any comment. If closed, you can reopen the issue at any time. Thank you for your contributions.
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Re: [I] [Bug]: Behavior change between Beam 2.66 and 2.71 causing severe buffering [beam]
Posted by "github-actions[bot] (via GitHub)" <gi...@apache.org>.
github-actions[bot] closed issue #37664: [Bug]: Behavior change between Beam 2.66 and 2.71 causing severe buffering
URL: https://github.com/apache/beam/issues/37664
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Re: [I] [Bug]: Behavior change between Beam 2.66 and 2.71 causing severe buffering [beam]
Posted by "stankiewicz (via GitHub)" <gi...@apache.org>.
stankiewicz commented on issue #37664:
URL: https://github.com/apache/beam/issues/37664#issuecomment-3953784229
is the same behaviour visible in runner v1 and runner v2?
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Re: [I] [Bug]: Behavior change between Beam 2.66 and 2.71 causing severe buffering [beam]
Posted by "raishakti-1983 (via GitHub)" <gi...@apache.org>.
raishakti-1983 commented on issue #37664:
URL: https://github.com/apache/beam/issues/37664#issuecomment-3937110281
Let me know if any other Graph or details are needed.
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Re: [I] [Bug]: Behavior change between Beam 2.66 and 2.71 causing severe buffering [beam]
Posted by "raishakti-1983 (via GitHub)" <gi...@apache.org>.
raishakti-1983 commented on issue #37664:
URL: https://github.com/apache/beam/issues/37664#issuecomment-3954296981
We haven't checked in Runner V2. Let us check and I will bet back to you.
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Re: [I] [Bug]: Behavior change between Beam 2.66 and 2.71 causing severe buffering [beam]
Posted by "github-actions[bot] (via GitHub)" <gi...@apache.org>.
github-actions[bot] commented on issue #37664:
URL: https://github.com/apache/beam/issues/37664#issuecomment-5410583514
This issue has been closed due to lack of activity. If you think that is incorrect, you can reopen the issue at any time.
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