DEVX-2271: Document additional cp-demo troubleshooting steps #297
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javabrett
approved these changes
Dec 3, 2020
mikebin
reviewed
Dec 3, 2020
docs/index.rst
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| @@ -280,7 +284,7 @@ Its embedded producer is configured to be idempotent, exactly-once in order sema | |||
| .. figure:: images/ksql_properties.png | |||
| :alt: image | |||
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| #. This example creates two streams ``EN_WIKIPEDIA_GT_1`` and ``EN_WIKIPEDIA_GT_1_COUNTS``, and the reason is to demonstrate how ksqlDB windows work. ``EN_WIKIPEDIA_GT_1`` counts occurences with a tumbling window, and for a given key it writes a `null` into the table on the first seen message. The underlying Kafka topic for ``EN_WIKIPEDIA_GT_1`` does not filter out those nulls, but to send just the counts greater than one downstream, there is a separate Kafka topic for ``EN_WIKIPEDIA_GT_1_COUNTS`` which does filter out those nulls (e.g., the query has a clause ``where ROWTIME is not null``). From the bash prompt, view those underlying Kafka topics. | |||
| #. This example creates two streams ``EN_WIKIPEDIA_GT_1`` and ``EN_WIKIPEDIA_GT_1_COUNTS``, and the reason is to demonstrate how ksqlDB windows work. ``EN_WIKIPEDIA_GT_1`` counts occurrences with a tumbling window, and for a given key it writes a `null` into the table on the first seen message. The underlying Kafka topic for ``EN_WIKIPEDIA_GT_1`` does not filter out those nulls, but to send just the counts greater than one downstream, there is a separate Kafka topic for ``EN_WIKIPEDIA_GT_1_COUNTS`` which does filter out those nulls (e.g., the query has a clause ``where ROWTIME is not null``). From the bash prompt, view those underlying Kafka topics. | |||
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EN_WIKIPEDIA_GT_1 is a topic name. EN_WIKIPEDIA_GT_1_STREAM is the stream name.
The where rowtime is not null condition is somewhat confusing, because the null-valued records actually have a timestamp. It's the fact that there's a where clause that causes the null-valued records to be silently dropped: confluentinc/ksql#5634
By the way, this behavior will likely be changing in ksqlDB 6.1.0: confluentinc/ksql#3558
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@mikebin 👍 thank you for surfacing this and flagging the potential behavior change. Since this PR is for troubleshooting steps (and spelling errors), I filed https://confluentinc.atlassian.net/browse/DEVX-2298 to track the issue separately.
ybyzek
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Description
https://confluentinc.atlassian.net/browse/DEVX-2271
What behavior does this PR change, and why?
.. code-block:: JSONAuthor Validation
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