jaymitdp opened a new issue, #35034:
URL: https://github.com/apache/beam/issues/35034
### What happened?
In the Apache Beam Python SDK, the GenerateSequence transform’s constructor
does not accept the period parameter, even though the Java SDK requires it when
elements_per_period is specified.
This means that if you want to use elements_per_period to generate a
rate-limited sequence, you cannot specify the accompanying period through the
Python SDK. This mismatch leads to a runtime failure inside the Java expansion
service with the error:
```
RuntimeError: java.lang.IllegalArgumentException: elements per period
specified, but no period specified
...
```
This prevents users from correctly controlling the rate of elements
generated by GenerateSequence from Python, making elements_per_period unusable
without period.
### Steps to Reproduce
1. In a Beam Python pipeline, attempt to instantiate GenerateSequence with
elements_per_period set, e.g.:
```
GenerateSequence(start=0, elements_per_period=1)
```
2. Notice that you cannot pass `period` to the constructor since it is not
accepted as an argument.
3. Run the pipeline on a runner using the expansion service (e.g.,
FlinkRunner).
4. Observe the runtime error about missing `period`.
### Expected Behavior
- The Python SDK GenerateSequence constructor should support a period
parameter.
- This would allow users to specify elements_per_period and period, aligning
with the Java SDK and the underlying runner’s requirements.
### Actual Behavior
- Python SDK constructor rejects `period` parameter (no support).
- Pipeline fails at runtime with an IllegalArgumentException from the Java
expansion service due to missing `period`.
### Environment
- Apache Beam Python SDK version: 2.65.0
- Runner: FlinkRunner (with expansion service)
- Java expansion service version: matches Beam 2.65.0
This gap between the Python SDK interface and the Java expansion service
causes confusing runtime failures and limits the usability of GenerateSequence
in Python for rate-limited sequences.
### Issue Priority
Priority: 2 (default / most bugs should be filed as P2)
### Issue Components
- [x] 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
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