Support Article
Unable to save records to Cassandra
SA-83806
Summary
Unable to save all records to an external Cassandra after reading messages from Kafka through a data flow.
Error Messages
No functional DDS nodes available after waiting 30 seconds
Unable to obtain session. Cassandra hasn't been started or is unavailable
Steps to Reproduce
- Run the data flow to read messages from a Kafka stream through a dataset.
- Save it to an external Cassandra through another dataset.
Root Cause
The source data (Kafka) consists of duplicate records and Cassandra only writes distinct records. Hence the difference in record count.
Resolution
Here's the explanation for the reported behavior:
The difference in the count of records between the source (Kafka) and destination (Cassandra) is due to distinct values which persist to the Cassandra table.
Write the results to a database table to perform a quick test. The distinct values count is the same as the record count in Cassandra keyspace.
Published December 2, 2021
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