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Elasticsearch with Custom Configuration Files

The KubeDB operator allows a user to deploy an Elasticsearch cluster with custom configuration files. The operator also allows the user to configure the security plugins such as X-Pack, SearchGurad, and OpenDistro. If the custom configuration files are not provided, the operator will start the cluster with default configurations.

Overview

Elasticsearch has three configuration files:

  • elasticsearch.yml: for configuring Elasticsearch
  • jvm.options: for configuring Elasticsearch JVM settings
  • log4j2.properties: for configuring Elasticsearch logging

In KubeDB managed Elasticsearch cluster, the configuration files are located at /usr/share/elasticsearch/config directory of Elasticsearch pods. To know more about configuring the Elasticsearch cluster see here.

The X-Pack security plugin has the following configuration files:

  • roles.yml - define roles and the associated permissions.
  • role_mapping.yml - define which roles should be assigned to each user based on their username, groups, or other metadata.

The SearchGuard security plugin has the following configuration files:

  • sg_config.yml - configure authenticators and authorization backends.
  • sg_roles.yml - define roles and the associated permissions.
  • sg_roles_mapping.yml - map backend roles, hosts, and users to roles.
  • sg_internal_users.yml - stores users, and hashed passwords in the internal user database.
  • sg_action_groups.yml - define named permission groups.
  • sg_tenants.yml - defines tenants for configuring the Kibana access.
  • sg_blocks.yml - defines blocked users and IP addresses.

The OpenDistro security plugin has the following configuration files:

  • internal_users.yml - contains any initial users that you want to add to the security plugin’s internal user database.
  • roles.yml - contains any initial roles that you want to add to the security plugin.
  • roles_mapping.yml - maps backend roles, hosts, and users to roles.
  • action_groups.yml - contains any initial action groups that you want to add to the security plugin.
  • tenants.yml - contains the tenant configurations.
  • nodes_dn.yml - contains nodesDN mapping name and corresponding values.

Custom Config Seceret

The custom configuration files are passed via a Kubernetes secret. The file names are the keys of the Secret with the file-contents as the values. The secret name needs to be mentioned in spec.configSecret.name of the Elasticsearch object.

apiVersion: kubedb.com/v1alpha2
kind: Elasticsearch
metadata:
  name: es-custom-config
  namespace: demo
spec:
  version: searchguard-7.9.3
  configSecret:
    name: es-custom-config
apiVersion: v1
kind: Secret
metadata:
  name: es-custom-config
  namespace: demo
stringData:
  elasticsearch.yml: |-
        logger.org.elasticsearch.discovery: DEBUG

How the resultant configuration files are generated?

  • YML: The default configuration file pre-stored at config directories is overwritten by the operator-generated configuration file (if any). Then the resultant configuration file is overwritten by the user-provided custom configuration file (if any). The yq tool is used to merge two YAML files.

    $ yq merge -i --overwrite file1.yml file2.yml
    
  • Non-YML: The default configuration file is replaced by the operator-generated one (if any). Then the resultant configuration file is replaced by the user-provided custom configuration file (if any).

    $ cp -f file2 file1
    

How to provide node-role specific configurations?

If an Elasticsearch cluster is running in the topology mode (ie. spec.topology is set), a user may want to provide node-role specific configurations, say configurations that will only be merged to master nodes. To achieve this, users need to add the node role as a prefix to the file name.

  • Format: <node-role>-<file-name>.extension
  • Samples:
    • data-elasticsearch.yml: Only applied to data nodes.
    • master-jvm.options: Only applied to master nodes.
    • ingest-log4j2.properties: Only applied to ingest nodes.
    • elasticsearch.yml: applied to all nodes.

How to provide additional files that are referenced from the configurations?

All these files provided via configSecret is stored in each Elasticsearch node (i.e. pod) at ES_CONFIG_DIR/custom_config/ ( i.e. /usr/share/elasticsearch/config/custom_config/) directory. So, user can use this path while configuring the Elasticsearch.

Next Steps

  • Learn how to use custom configuration in combined cluster from here.
  • Learn how to use custom configuration in topology cluster from here.