Make KAFKA_RESCHEDULE_MS a Kafka table setting #90112
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azat
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Nov 15, 2025
| SELECT level, sum(total) FROM daily GROUP BY level; | ||
| ``` | ||
| To improve performance, received messages are grouped into blocks the size of [max_insert_block_size](../../../operations/settings/settings.md#max_insert_block_size). If the block wasn't formed within [stream_flush_interval_ms](/operations/settings/settings#stream_flush_interval_ms) milliseconds, the data will be flushed to the table regardless of the completeness of the block. | ||
| To improve performance, received messages are grouped into blocks the size of [max_insert_block_size](../../../operations/settings/settings.md#max_insert_block_size). If the block wasn't formed within [stream_flush_interval_ms](/operations/settings/settings#stream_flush_interval_ms) milliseconds, the data will be flushed to the table regardless of the completeness of the block. |
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| To improve performance, received messages are grouped into blocks the size of [max_insert_block_size](../../../operations/settings/settings.md#max_insert_block_size). If the block wasn't formed within [stream_flush_interval_ms](/operations/settings/settings#stream_flush_interval_ms) milliseconds, the data will be flushed to the table regardless of the completeness of the block. | |
| To improve performance, received messages are grouped into blocks the size of [max_insert_block_size](../../../operations/settings/settings.md#max_insert_block_size). If the block wasn't formed within [stream_flush_interval_ms](/operations/settings/settings#stream_flush_interval_ms) milliseconds, the data will be flushed to the table regardless of the completeness of the block. |
| main_configs=["configs/kafka.xml", "configs/named_collection.xml"], | ||
| user_configs=["configs/users.xml"], | ||
| with_kafka=True, | ||
| with_zookeeper=True, # For Replicated Table |
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| with_zookeeper=True, # For Replicated Table | |
| with_zookeeper=True, # For Kafka2 |
| instance.wait_for_log_line(f"{kafka_table}.*Committed offset 20000") | ||
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| logging.debug("Timestamps: %s", instance.query(f"SELECT max(consume_ts), min(consume_ts) FROM test.{kafka_table}_destination")) | ||
| assert int(instance.query(f"SELECT max(consume_ts) - min(consume_ts) FROM test.{kafka_table}_destination")) < 8 |
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What is this test is about? Why 8?
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Ah, this should be removed. I used test_batch_slow_1.py as a template for this, and this test comes from that. Sorry for the confusion. I will address Monday alongside your suggestions
| instance.wait_for_log_line(f"{kafka_table}.*Committed offset 50") | ||
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| # Wait a bit for stream to stall and log the reschedule message | ||
| time.sleep(2.0) |
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I guess we can remove this, since wait_for_log_line should have retries that are greater then 2 secs in total
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Changelog entry (a [user-readable short description]
Add
kafka_consumer_reschedule_msas a tunableKafkatable engine setting in order to adjust how long consumers sleep for new data.Documentation entry for user-facing changes
This pull request is to address this issue that I reported: #89204
Essentially, if one were to set
kafka_flush_interval_msto be quite low (say, 250ms), one would expect that data would make its way to the downstream table in ~250ms. However, this is not the case, even if ingestion is happening very quickly. The reason is because there is a hardcoded 500ms stall that happens (a) when a consumer sees no messages or (b) when 1 minute passes.This means that ingestion can happen much later than expected, as noted in my investigation. To fix, allow end users to tune this param while keeping the 500ms default.