Configures a Kafka Bridge cluster.

Configuration options relate to:

* Kafka cluster bootstrap address
* Security (encryption, authentication, and authorization)
* Consumer configuration
* Producer configuration
* HTTP configuration

[id='property-kafka-bridge-logging-{context}']
= `logging`

Kafka Bridge has its own configurable loggers:

* `rootLogger.level`
* `logger.__<operation-id>__`

You can replace `_<operation-id>_` in the `logger.__<operation-id>__` logger to set log levels for specific operations:

* `createConsumer`
* `deleteConsumer`
* `subscribe`
* `unsubscribe`
* `poll`
* `assign`
* `commit`
* `send`
* `sendToPartition`
* `seekToBeginning`
* `seekToEnd`
* `seek`
* `healthy`
* `ready`
* `openapi`

Each operation is defined according OpenAPI specification, and has a corresponding API endpoint through which the bridge receives requests from HTTP clients.
You can change the log level on each endpoint to create fine-grained logging information about the incoming and outgoing HTTP requests.

Each logger has to be configured assigning it a `name` as `http.openapi.operation.__<operation-id>__`.
For example, configuring the logging level for the `send` operation logger means defining the following:

```
logger.send.name = http.openapi.operation.send
logger.send.level = DEBUG
```

Kafka Bridge uses the Apache `log4j2` logger implementation.
Loggers are defined in the `log4j2.properties` file, which has the following default configuration for `healthy` and `ready` endpoints:

```
logger.healthy.name = http.openapi.operation.healthy
logger.healthy.level = WARN
logger.ready.name = http.openapi.operation.ready
logger.ready.level = WARN
```
The log level of all other operations is set to `INFO` by default.

Use the `logging` property to configure loggers and logger levels.

You can set the log levels by specifying the logger and level directly (inline) or use a custom (external) ConfigMap.
If a ConfigMap is used, you set `logging.valueFrom.configMapKeyRef.name` property to the name of the ConfigMap containing the external logging configuration.
The `logging.valueFrom.configMapKeyRef.name` and `logging.valueFrom.configMapKeyRef.key` properties are mandatory.
Default logging is used if the `name` or `key` is not set.
Inside the ConfigMap, the logging configuration is described using `log4j.properties`.
For more information about log levels, see {ApacheLoggers}.

Here we see examples of `inline` and `external` logging.

.Inline logging
[source,yaml,subs="+quotes,attributes"]
----
apiVersion: {KafkaApiVersion}
kind: KafkaBridge
spec:
  # ...
  logging:
    type: inline
    loggers:
      rootLogger.level: INFO
      # enabling DEBUG just for send operation
      logger.send.name: "http.openapi.operation.send"
      logger.send.level: DEBUG
  # ...
----

.External logging
[source,yaml,subs="+quotes,attributes"]
----
apiVersion: {KafkaApiVersion}
kind: KafkaBridge
spec:
  # ...
  logging:
    type: external
    valueFrom:
      configMapKeyRef:
        name: customConfigMap
        key: bridge-logj42.properties
  # ...
----

Any available loggers that are not configured have their level set to `OFF`.

If the Kafka Bridge was deployed using the Cluster Operator,
changes to Kafka Bridge logging levels are applied dynamically.

If you use external logging, a rolling update is triggered when logging appenders are changed.

.Garbage collector (GC)

Garbage collector logging can also be enabled (or disabled) using the xref:con-common-configuration-garbage-collection-reference[`jvmOptions` property].
