Change Data Capture (CDC) logging
Change Data Capture (CDC) logging captures and tracks data that has changed. CDC logging is configured per table, with limits on the amount of disk space to consume for storing the CDC logs. CDC logs use the same binary format as the commit log.
The location of the CDC directory depends on the type of installation:
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Package installations:
/var/lib/cassandra/cdc_raw -
Tarball installations:
/var/lib/cassandra/cdc_raw
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When all tables having mutations in a completed commitlog segment are flushed, a hard link to that commitlog segment is created in the If the disk space limit is reached, CDC-enabled tables reject writes until space is freed. |
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Before enabling CDC logging, define a plan for moving and consuming the CDC log information. DataStax recommends a physical device for the CDC log that is separate from the data directories.
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Enable CDC logging and configure CDC directories and space in
cassandra.yaml.The location of the
cassandra.yamlfile depends on the type of installation:-
Package installations and Installer-Services installations:
/etc/dse/cassandra/cassandra.yaml -
Tarball installations and Installer-No Services installations:
<installation_location>/resources/cassandra/conf/cassandra.yaml
For example, to enable CDC logging with default values:
cdc_enabled: true cdc_total_space_in_mb: 4096 cdc_free_space_check_interval_ms: 250 cdc_raw_directory: /var/lib/cassandra/cdc_raw -
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To enable CDC logging for a database table, create or alter the table with the table property.
For example, to enable CDC logging on the cycling table:
ALTER TABLE cycling WITH cdc=true;
