// This module is included in the following files:
//
// using/using.adoc

[id='con-common-configuration-properties-{context}']
== Common configuration properties

Common configuration properties apply to more than one resource.

[id='con-common-configuration-replicas-{context}']
=== `replicas`

Use the `replicas` property to configure replicas.

The type of replication depends on the resource.

* `KafkaTopic` uses a replication factor to configure the number of replicas of each partition within a Kafka cluster.
* Kafka components use replicas to configure the number of pods in a deployment to provide better availability and scalability.

NOTE: When running a Kafka component on Kubernetes it may not be necessary to run multiple replicas for high availability.
When the node where the component is deployed crashes, Kubernetes will automatically reschedule the Kafka component pod to a different node.
However, running Kafka components with multiple replicas can provide faster failover times as the other nodes will be up and running.

[id='con-common-configuration-bootstrap-{context}']
=== `bootstrapServers`

Use the `bootstrapServers` property to configure a list of bootstrap servers.

The bootstrap server lists can refer to Kafka clusters that are not deployed in the same Kubernetes cluster.
They can also refer to a Kafka cluster not deployed by Strimzi.

If on the same Kubernetes cluster, each list must ideally contain the Kafka cluster bootstrap service which is named `_CLUSTER-NAME_-kafka-bootstrap` and a port number.
If deployed by Strimzi but on different Kubernetes clusters, the list content depends on the approach used for exposing the clusters (routes, ingress, nodeports or loadbalancers).

When using Kafka with a Kafka cluster not managed by Strimzi, you can specify the bootstrap servers list according to the configuration of the given cluster.

[id='con-common-configuration-ssl-{context}']
=== `ssl`

Use the three allowed `ssl` configuration options for client connection using a specific _cipher suite_ for a TLS version.
A cipher suite combines algorithms for secure connection and data transfer.

You can also configure the `ssl.endpoint.identification.algorithm` property to enable or disable hostname verification.

.Example SSL configuration
[source,yaml,subs="attributes+"]
----
# ...
spec:
  config:
    ssl.cipher.suites: "TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384" <1>
    ssl.enabled.protocols: "TLSv1.2" <2>
    ssl.protocol: "TLSv1.2" <3>
    ssl.endpoint.identification.algorithm: HTTPS <4>
# ...
----
<1> The cipher suite for TLS using a combination of `ECDHE` key exchange mechanism, `RSA` authentication algorithm,
`AES` bulk encyption algorithm and `SHA384` MAC algorithm.
<2> The SSl protocol `TLSv1.2` is enabled.
<3> Specifies the `TLSv1.2` protocol to generate the SSL context.
Allowed values are `TLSv1.1` and `TLSv1.2`.
<4> Hostname verification is enabled by setting to `HTTPS`. An empty string disables the verification.

[id='con-common-configuration-trusted-certificates-{context}']
=== `trustedCertificates`

Having set `tls` to configure TLS encryption, use the `trustedCertificates` property to provide a list of secrets with key names under which the certificates are stored in X.509 format.

You can use the secrets created by the Cluster Operator for the Kafka cluster,
or you can create your own TLS certificate file, then create a `Secret` from the file:

[source,shell,subs=+quotes]
kubectl create secret generic _MY-SECRET_ \
--from-file=_MY-TLS-CERTIFICATE-FILE.crt_

.Example TLS encryption configuration
[source,yaml,subs=attributes+]
----
tls:
  trustedCertificates:
    - secretName: my-cluster-cluster-cert
      certificate: ca.crt
    - secretName: my-cluster-cluster-cert
      certificate: ca2.crt
----

If certificates are stored in the same secret, it can be listed multiple times.

If you want to enable TLS, but use the default set of public certification authorities shipped with Java,
you can specify `trustedCertificates` as an empty array:

.Example of enabling TLS with the default Java certificates
[source,yaml,subs=attributes+]
----
tls:
  trustedCertificates: []
----

For information on configuring TLS client authentication, see xref:type-KafkaClientAuthenticationTls-reference[`KafkaClientAuthenticationTls` schema reference].

[id='con-common-configuration-resources-{context}']
=== `resources`

Configure resource _requests_ and _limits_ to control resources for Strimzi containers.
You can specify requests and limits for `memory` and `cpu` resources.
The requests should be enough to ensure a stable performance of Kafka.  

How you configure resources in a production environment depends on a number of factors.
For example, applications are likely to be sharing resources in your Kubernetes cluster.

For Kafka, the following aspects of a deployment can impact the resources you need:

* Throughput and size of messages
* The number of network threads handling messages
* The number of producers and consumers
* The number of topics and partitions

The values specified for resource requests are reserved and always available to a container.
Resource limits specify the maximum resources that can be consumed by a given container.
The amount between the request and limit is not reserved and might not be always available.
A container can use the resources up to the limit only when they are available.
Resource limits are temporary and can be reallocated.

.Resource request and limit
image:common-config-resources.png[Boundaries of a resource request and limit]

If you set limits without requests or vice versa, Kubernetes uses the same value for both.
Setting equal requests and limits for resources guarantees quality of service, as
Kubernetes will not kill containers unless they exceed their limits.

You can configure resource requests and limits for one or more supported resources.

.Example resource configuration
[source,yaml,subs="+attributes"]
----
apiVersion: {KafkaApiVersion}
kind: Kafka
metadata:
  name: my-cluster
spec:
  kafka:
    #...
    resources:
      requests:
        memory: 64Gi
        cpu: "8"
      limits:
        memory: 64Gi
        cpu: "12"
  entityOperator:
    #...
    topicOperator:
      #...
      resources:
        requests:
          memory: 512Mi
          cpu: "1"
        limits:
          memory: 512Mi
          cpu: "1"
----

Resource requests and limits for the Topic Operator and User Operator are set in the `Kafka` resource.

If the resource request is for more than the available free resources in the Kubernetes cluster, the pod is not scheduled.

NOTE: Strimzi uses the Kubernetes syntax for specifying `memory` and `cpu` resources.
For more information about managing computing resources on Kubernetes, see {K8sManagingComputingResources}.

Memory resources:: When configuring memory resources, consider the total requirements of the components.
+
--
Kafka runs inside a JVM and uses an operating system page cache to store message data before writing to disk.
The memory request for Kafka should fit the JVM heap and page cache.
You can xref:con-common-configuration-jvm-{context}[configure the `jvmOptions` property] to control the minimum and maximum heap size.

Other components don't rely on the page cache.
You can configure memory resources without configuring the `jvmOptions` to control the heap size.

Memory requests and limits are specified in megabytes, gigabytes, mebibytes, and gibibytes.
Use the following suffixes in the specification:

* `M` for megabytes
* `G` for gigabytes
* `Mi` for mebibytes
* `Gi` for gibibytes

.Example resources using different memory units
[source,yaml,subs="attributes+"]
----
# ...
resources:
  requests:
    memory: 512Mi
  limits:
    memory: 2Gi
# ...
----

For more details about memory specification and additional supported units, see {K8sMeaningOfMemory}.
--

CPU resources:: A CPU request should be enough to give a reliable performance at any time.
CPU requests and limits are specified as _cores_ or _millicpus_/_millicores_.
+
--
CPU cores are specified as integers (`5` CPU core) or decimals (`2.5` CPU core).
1000 _millicores_ is the same as `1` CPU core.

.Example CPU units
[source,yaml,subs="attributes+"]
----
# ...
resources:
  requests:
    cpu: 500m
  limits:
    cpu: 2.5
# ...
----

The computing power of 1 CPU core may differ depending on the platform where Kubernetes is deployed.

For more information on CPU specification, see {K8sMeaningOfCpu}.
--

[id='con-common-configuration-images-{context}']
=== `image`

Use the `image` property to configure the container image used by the component.

Overriding container images is recommended only in special situations where you need to use a different container registry or a customized image.

For example, if your network does not allow access to the container repository used by Strimzi, you can copy the Strimzi images or build them from the source.
However, if the configured image is not compatible with Strimzi images, it might not work properly.

A copy of the container image might also be customized and used for debugging.

You can specify which container image to use for a component using the `image` property in the following resources:

* `Kafka.spec.kafka`
* `Kafka.spec.zookeeper`
* `Kafka.spec.entityOperator.topicOperator`
* `Kafka.spec.entityOperator.userOperator`
* `Kafka.spec.entityOperator.tlsSidecar`
* `Kafka.spec.jmxTrans`
* `KafkaConnect.spec`
* `KafkaMirrorMaker.spec`
* `KafkaMirrorMaker2.spec`
* `KafkaBridge.spec`

*Configuring the `image` property for Kafka, Kafka Connect, and Kafka MirrorMaker*

Kafka, Kafka Connect, and Kafka MirrorMaker support multiple versions of Kafka.
Each component requires its own image.
The default images for the different Kafka versions are configured in the following environment variables:

* `STRIMZI_KAFKA_IMAGES`
* `STRIMZI_KAFKA_CONNECT_IMAGES`
* `STRIMZI_KAFKA_MIRROR_MAKER_IMAGES`

These environment variables contain mappings between the Kafka versions and their corresponding images.
The mappings are used together with the `image` and `version` properties:

* If neither `image` nor `version` are given in the custom resource then the `version` will default to the Cluster Operator's default Kafka version, and the image will be the one corresponding to this version in the environment variable.

* If `image` is given but `version` is not, then the given image is used and the `version` is assumed to be the Cluster Operator's default Kafka version.

* If `version` is given but `image` is not, then the image that corresponds to the given version in the environment variable is used.

* If both `version` and `image` are given, then the given image is used. The image is assumed to contain a Kafka image with the given version.

The `image` and `version` for the different components can be configured in the following properties:

* For Kafka in `spec.kafka.image` and `spec.kafka.version`.
* For Kafka Connect and Kafka MirrorMaker in `spec.image` and `spec.version`.

WARNING: It is recommended to provide only the `version` and leave the `image` property unspecified.
This reduces the chance of making a mistake when configuring the custom resource.
If you need to change the images used for different versions of Kafka, it is preferable to configure the Cluster Operator's environment variables.

*Configuring the `image` property in other resources*

For the `image` property in the other custom resources, the given value will be used during deployment.
If the `image` property is missing, the `image` specified in the Cluster Operator configuration will be used.
If the `image` name is not defined in the Cluster Operator configuration, then the default value will be used.

* For Topic Operator:
. Container image specified in the `STRIMZI_DEFAULT_TOPIC_OPERATOR_IMAGE` environment variable from the Cluster Operator configuration.
. `{DockerTopicOperator}` container image.
* For User Operator:
. Container image specified in the `STRIMZI_DEFAULT_USER_OPERATOR_IMAGE` environment variable from the Cluster Operator configuration.
. `{DockerUserOperator}` container image.
* For Entity Operator TLS sidecar:
. Container image specified in the `STRIMZI_DEFAULT_TLS_SIDECAR_ENTITY_OPERATOR_IMAGE` environment variable from the Cluster Operator configuration.
. `{DockerEntityOperatorStunnel}` container image.
* For Kafka Exporter:
. Container image specified in the `STRIMZI_DEFAULT_KAFKA_EXPORTER_IMAGE` environment variable from the Cluster Operator configuration.
. `{DockerKafka}` container image.
* For Kafka Bridge:
. Container image specified in the `STRIMZI_DEFAULT_KAFKA_BRIDGE_IMAGE` environment variable from the Cluster Operator configuration.
. `{DockerKafkaBridge}` container image.
* For Kafka broker initializer:
. Container image specified in the `STRIMZI_DEFAULT_KAFKA_INIT_IMAGE` environment variable from the Cluster Operator configuration.
. `{DockerKafkaInit}` container image.
* For Kafka jmxTrans:
. Container image specified in the `STRIMZI_DEFAULT_JMXTRANS_IMAGE` environment variable from the Cluster Operator configuration.
. `{DockerJmxtrans}` container image.

.Example container image configuration
[source,yaml,subs=attributes+]
----
apiVersion: {KafkaApiVersion}
kind: Kafka
metadata:
  name: my-cluster
spec:
  kafka:
    # ...
    image: my-org/my-image:latest
    # ...
  zookeeper:
    # ...
----

[id='con-common-configuration-healthchecks-{context}']
=== `livenessProbe` and `readinessProbe` healthchecks

Use the `livenessProbe` and `readinessProbe` properties to configure healthcheck probes supported in Strimzi.

Healthchecks are periodical tests which verify the health of an application.
When a Healthcheck probe fails, Kubernetes assumes that the application is not healthy and attempts to fix it.

For more details about the probes, see {K8sLivenessReadinessProbes}.

Both `livenessProbe` and `readinessProbe` support the following options:

* `initialDelaySeconds`
* `timeoutSeconds`
* `periodSeconds`
* `successThreshold`
* `failureThreshold`

.Example of liveness and readiness probe configuration
[source,yaml,subs="attributes+"]
----
# ...
readinessProbe:
  initialDelaySeconds: 15
  timeoutSeconds: 5
livenessProbe:
  initialDelaySeconds: 15
  timeoutSeconds: 5
# ...
----

For more information about the `livenessProbe` and `readinessProbe` options, see xref:type-Probe-reference[Probe schema reference].

[id='con-common-configuration-prometheus-{context}']
=== `metricsConfig`

Use the `metricsConfig` property to enable and configure Prometheus metrics.

The `metricsConfig` property contains a reference to a ConfigMap that has additional configurations for the {JMXExporter}.
Strimzi supports Prometheus metrics using Prometheus JMX exporter to convert the JMX metrics supported by Apache Kafka and ZooKeeper to Prometheus metrics.

To enable Prometheus metrics export without further configuration, you can reference a ConfigMap containing an empty file under `metricsConfig.valueFrom.configMapKeyRef.key`.
When referencing an empty file, all metrics are exposed as long as they have not been renamed.

.Example ConfigMap with metrics configuration for Kafka
[source,yaml,subs="+attributes"]
----
kind: ConfigMap
apiVersion: v1
metadata:
  name: my-configmap
data:
  my-key: |
    lowercaseOutputName: true
    rules:
    # Special cases and very specific rules
    - pattern: kafka.server<type=(.+), name=(.+), clientId=(.+), topic=(.+), partition=(.*)><>Value
      name: kafka_server_$1_$2
      type: GAUGE
      labels:
       clientId: "$3"
       topic: "$4"
       partition: "$5"
    # further configuration
----

.Example metrics configuration for Kafka
[source,yaml,subs="+attributes"]
----
apiVersion: {KafkaApiVersion}
kind: Kafka
metadata:
  name: my-cluster
spec:
  kafka:
    # ...
    metricsConfig:
      type: jmxPrometheusExporter
      valueFrom:
        configMapKeyRef:
          name: my-config-map
          key: my-key
    # ...
  zookeeper:
    # ...
----

When metrics are enabled, they are exposed on port 9404.

When the `metricsConfig` (or deprecated `metrics`) property is not defined in the resource, the Prometheus metrics are disabled.

For more information about setting up and deploying Prometheus and Grafana, see link:{BookURLDeploying}#assembly-metrics-setup-str[Introducing Metrics to Kafka] in the _Deploying and Upgrading Strimzi_ guide.

[id='con-common-configuration-jvm-{context}']
=== `jvmOptions`

The following Strimzi components run inside a Java Virtual Machine (JVM):

* Apache Kafka
* Apache ZooKeeper
* Apache Kafka Connect
* Apache Kafka MirrorMaker
* Strimzi Kafka Bridge

To optimize their performance on different platforms and architectures, you configure the `jvmOptions` property in the following resources:

* `Kafka.spec.kafka`
* `Kafka.spec.zookeeper`
* `Kafka.spec.entityOperator.userOperator`
* `Kafka.spec.entityOperator.topicOperator`
* `Kafka.spec.cruiseControl`
* `KafkaConnect.spec`
* `KafkaMirrorMaker.spec`
* `KafkaMirrorMaker2.spec`
* `KafkaBridge.spec`

You can specify the following options in your configuration:

`-Xms`:: Minimum initial allocation heap size when the JVM starts.
`-Xmx`:: Maximum heap size.
`-XX`:: Advanced runtime options for the JVM.
`javaSystemProperties`:: Additional system properties.
`gcLoggingEnabled`:: xref:con-common-configuration-garbage-collection-{context}[Enables garbage collector logging].

The full schema of `jvmOptions` is described in xref:type-JvmOptions-reference[`JvmOptions` schema reference].

NOTE: The units accepted by JVM settings, such as `-Xmx` and `-Xms`, are the same units accepted by the JDK `java` binary in the corresponding image.
Therefore, `1g` or `1G` means 1,073,741,824 bytes, and `Gi` is not a valid unit suffix.
This is different from the units used for xref:con-common-configuration-resources-reference[memory requests and limits], which follow the Kubernetes convention where `1G` means 1,000,000,000 bytes, and `1Gi` means 1,073,741,824 bytes

.`-Xms` and `-Xmx` options

The default values used for `-Xms` and `-Xmx` depend on whether there is a xref:con-common-configuration-resources-reference[memory request] limit configured for the container.

* If there is a memory limit, the JVM's minimum and maximum memory is set to a value corresponding to the limit.
* If there is no memory limit, the JVM's minimum memory is set to `128M`. The JVM's maximum memory is not defined to allow the memory to increase as needed. This is ideal for single node environments in test and development.

Before setting `-Xmx` explicitly, consider the following:

* Total JVM memory usage can be a lot more than the maximum heap size. Try experimenting to find a value for `-Xmx` that makes the best use of the container's memory request without exceeding it.
* Setting an appropriate Kubernetes memory request.
** Kubernetes might kill the container if there is pressure on memory from other pods running on the node.
** Kubernetes might schedule the container to a node with insufficient memory.
If `-Xms` is set to `-Xmx`, the container will crash immediately; if not, the container will crash at a later time.

It is _recommended_ to:

* Set the memory request and the memory limit to the same value
* Use a memory request that is at least 4.5 × the `-Xmx`
* Consider setting `-Xms` to the same value as `-Xmx`

In this example, the JVM uses 2 GiB (=2,147,483,648 bytes) for its heap.
Its total memory usage is approximately 8GiB.

.Example `-Xmx` and `-Xms` configuration
[source,yaml,subs=attributes+]
----
# ...
jvmOptions:
  "-Xmx": "2g"
  "-Xms": "2g"
# ...
----

Setting the same value for initial (`-Xms`) and maximum (`-Xmx`) heap sizes avoids the JVM having to allocate memory after startup, at the cost of possibly allocating more heap than is really needed.

IMPORTANT: Containers performing lots of disk I/O, such as Kafka broker containers, require available memory for use as an operating system page cache.
On such containers, the requested memory should be significantly higher than the memory used by the JVM.

.-XX option

`-XX` options are used to configure the `KAFKA_JVM_PERFORMANCE_OPTS` option of Apache Kafka.

.Example `-XX` configuration
[source,yaml,subs=attributes+]
----
jvmOptions:
  "-XX":
    "UseG1GC": true
    "MaxGCPauseMillis": 20
    "InitiatingHeapOccupancyPercent": 35
    "ExplicitGCInvokesConcurrent": true
----

.JVM options resulting from the `-XX` configuration
[source]
----
-XX:+UseG1GC -XX:MaxGCPauseMillis=20 -XX:InitiatingHeapOccupancyPercent=35 -XX:+ExplicitGCInvokesConcurrent -XX:-UseParNewGC
----

NOTE: When no `-XX` options are specified, the default Apache Kafka configuration of `KAFKA_JVM_PERFORMANCE_OPTS` is used.

.`javaSystemProperties`

`javaSystemProperties` are used to configure additional Java system properties, such as debugging utilities.

.Example `javaSystemProperties` configuration
[source,yaml,subs=attributes+]
----
jvmOptions:
  javaSystemProperties:
    - name: javax.net.debug
      value: ssl
----


[id='con-common-configuration-garbage-collection-{context}']
=== Garbage collector logging

The `jvmOptions` property also allows you to enable and disable garbage collector (GC) logging.
GC logging is disabled by default.
To enable it, set the `gcLoggingEnabled` property as follows:

.Example GC logging configuration
[source,yaml,subs=attributes+]
----
# ...
jvmOptions:
  gcLoggingEnabled: true
# ...
----
