Configuration & Environment Overrides

The cluster definition also supports overriding configuration properties and environment variables, either per role or per role group, where the more specific override (role group) has precedence over the less specific one (role).

Do not override port numbers. This will lead to cluster malfunction.

Configuration Overrides

Apache NiFi runtime configuration is stored in several files listed below. The configOverrides block enables you to customize parameters in these files. The complete list of the configuration options can be found in the Apache NiFi documentation.

The following files can be edited directly via the configOverrides mechanism:

  • bootstrap.conf

  • nifi.properties

  • security.properties

Overrides are key, value pairs defined under one of the configuration files from the list above. They must match the names values as expected by NiFi. In the example below, a property nifi.flow.configuration.archive.enabled is being explicitly set to 'false', overriding the default value.

The following snippet shows how to disable workflow file backups in the NifiCluster definition:

  nodes:
    configOverrides:
      nifi.properties:
        nifi.flow.configuration.archive.enabled: false
Please be aware that by overriding config settings in this section you have a very high risk of breaking things, because the product does not behave the way the Stackable Operator for Apache NiFi expects it to behave anymore.

The security.properties file

The security.properties file is used to configure JVM security properties. It is very seldom that users need to tweak any of these, but there is one use-case that stands out, and that users need to be aware of: the JVM DNS cache.

The JVM manages its own cache of successfully resolved host names as well as a cache of host names that cannot be resolved. Some products of the Stackable platform are very sensible to the contents of these caches and their performance is heavily affected by them. As of version 1.21.0 Apache Nifi performs poorly if the positive cache is disabled. To cache resolved host names, and thus increase the performance your Nifi cluster, you can configure the TTL of entries in the positive cache like this:

  nodes:
    configOverrides:
      security.properties:
        networkaddress.cache.ttl: "30"
        networkaddress.cache.negative.ttl: "0"
The operator configures DNS caching by default as shown in the example above.

For details on the JVM security see https://docs.oracle.com/en/java/javase/11/security/java-security-overview1.html

Environment Variables

Environment variables can be (over)written by adding the envOverrides property.

For example per role group:

nodes:
  roleGroups:
    default:
      config: {}
      replicas: 1
      envOverrides:
        MY_ENV_VAR: "MY_VALUE"

or per role:

nodes:
  envOverrides:
    MY_ENV_VAR: "MY_VALUE"
  roleGroups:
    default:
      config: {}
      replicas: 1