FAQ about features of Elasticsearch clusters

If you're considering implementing Alibaba Cloud Elasticsearch as your environment, you likely have some questions about its features and capabilities.

Can I upgrade or downgrade the version of an Elasticsearch cluster?

You can upgrade the versions of clusters only from V5.5 to V5.6, from V5.6 to V6.3, or from V6.3 to V6.7.

If you want to perform upgrades between other versions or perform version downgrades, purchase an Elasticsearch cluster of the desired version. Then, migrate data from the original cluster to the new cluster and unsubscribe from or release the original cluster.

For information about how to upgrade the version of an Elasticsearch cluster, see Upgrade the version of a cluster.
For information about how to create an Elasticsearch cluster, see Create an Alibaba Cloud Elasticsearch cluster.
For information about how to migrate data between Elasticsearch clusters, see Data migration between Alibaba Cloud Elasticsearch clusters.
For information about how to unsubscribe from an unexpired subscription Elasticsearch cluster, see Unsubscription and refund policies. For information about how to release a pay-as-you-go Elasticsearch cluster, see Release a cluster.

Can I log on to an Elasticsearch cluster over SSH and modify the configuration of the cluster?

No, for security purposes, you are not allowed to log on to your Elasticsearch cluster over SSH. If you want to modify the configuration of your cluster, use the cluster configuration feature of Elasticsearch. For more information, see Overview of cluster configuration.

Is Logstash V6.7 compatible with Elasticsearch V6.3?

Yes, Logstash V6.7 is compatible with Elasticsearch V6.3. For more information, see Compatibility matrixes.

Can Elasticsearch be used as a data source of Quick BI?

No, Elasticsearch cannot be used as a data source of Quick BI. You can use Kibana to analyze data and present analysis results.

Does Elasticsearch support scoring plug-ins?

Yes, Elasticsearch supports scoring plug-ins. When you create an index, Elasticsearch allows you to create a tokenizer. This way, when you search for data, Elasticsearch uses a scoring plug-in to sort search results by score. For more information, see Step 5: Search for data.

Does Elasticsearch support LDAP?

Yes, Elasticsearch supports Lightweight Directory Access Protocol (LDAP). If you want to use LDAP to authenticate the requests that are sent to your Elasticsearch cluster, you must deploy an on-premises Elasticsearch cluster of the same version and use this cluster to conduct an authentication test. If LDAP runs as expected, configure your cluster to support LDAP based on the configurations of the on-premises Elasticsearch cluster. For more information, see Use X-Pack to configure LDAP authentication.

Does Alibaba Cloud provide Elasticsearch SDK for Java?

Yes, Alibaba Cloud provides Elasticsearch SDK for Java. Different Elasticsearch versions use different SDKs. For more information, see Java API.

How do I view the kernel version of an Elasticsearch cluster?

By default, Elasticsearch clusters use the kernel of the latest version. For more information about kernel versions, see AliES release notes. If your cluster does not use the kernel of the latest version, the A new kernel patch is available message appears on the Basic Information page of your cluster. You can click the message to view the current kernel version of your cluster.

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When am I allowed to forcefully restart an Elasticsearch cluster? What is the impact of a forced restart?

If your Elasticsearch cluster is in an abnormal state (indicated by the color red or yellow) and you want to restart the cluster, you can forcefully restart the cluster. During the forced restart, your Elasticsearch service may be unstable, data may be lost, or data read and write operations may fail. Proceed with caution.

How do I check whether the vulnerability in Apache Log4j 2 is fixed for my Elasticsearch cluster?

The vulnerability is fixed after your Elasticsearch cluster is restarted. For more information, see [Vulnerability notice] RCE vulnerability in Apache Log4j 2.

Do I need to upgrade the version of my Elasticsearch cluster to fix the vulnerability in Apache Log4j 2?

No, you do not need to upgrade the version of your Elasticsearch cluster. You need to only follow the instructions provided in Procedure to fix the vulnerability.

How do I enable communication between Elasticsearch clusters that reside in different regions over an internal network?

You can use one of the following methods to enable communication between Elasticsearch clusters that reside in different regions over an internal network:

Create a VPC peering connection between the VPCs in which the Elasticsearch clusters are deployed. For more information, see Create and manage a VPC peering connection.
Use a Cloud Enterprise Network (CEN) instance. For more information, see Step 1: Network planning.

How do I migrate data to an Alibaba Cloud Elasticsearch cluster?

You can migrate data to an Alibaba Cloud Elasticsearch cluster from another Alibaba Cloud Elasticsearch cluster, a self-managed Elasticsearch cluster, or a third-party Elasticsearch source. The data migration solution and tool vary based on the data migration scenario. For more information, see Select a data migration solution.

Can I enable HTTPS for an Elasticsearch cluster that does not contain client nodes?

Before you enable HTTPS for an Elasticsearch cluster of a version other than the following versions, you must make sure that the cluster contains client nodes.

V7.16 and later

If an Elasticsearch cluster is of one of the preceding versions and contains client nodes, you can disable the client nodes for the cluster. If an Elasticsearch cluster is of a version other than the preceding versions and contains client nodes, you cannot release, unsubscribe from, or disable the client nodes for the cluster.

For security purposes, after you enable HTTPS for an Elasticsearch cluster, the system regularly maintains and updates the certificates on which the cluster depends. You cannot perform a rolling update for certificates installed on data nodes in Elasticsearch clusters of V7.10 or earlier. To reduce the impact of a node restart on online services during a certificate update, the system deploys the certificates on client nodes, which are used to forward requests. When you enable HTTPS for an Elasticsearch cluster that does not contain client nodes, the system displays a message to prompt you to purchase client nodes for the cluster. You must purchase client nodes for the cluster before you can enable HTTPS for the cluster. For more information, see Enable HTTPS.

What is the maximum number of shards that can be allocated for indexes on a single data node in an Elasticsearch cluster?

Alibaba Cloud Elasticsearch allows you to allocate a maximum of 1,000 shards for indexes on a single data node in Elasticsearch V7.X clusters. The number of shards that can be allocated for indexes on a single data node is not limited for Elasticsearch clusters of other versions. You must configure shards for indexes on a single data node based on the specifications of the Elasticsearch cluster. For more information, see Evaluate specifications and storage capacity and Size your shards.

You can run the following command in which the max_shards_per_node parameter is configured to temporarily change the maximum number of shards that a single data node can store:

PUT /_cluster/settings
{
   "transient": {
      "cluster": {
        "max_shards_per_node":10000
      }
   }
}

How are indexes whose names start with .monitoring-es generated? What can I do with such indexes?

By default, the X-Pack monitoring component collects monitoring data from an Elasticsearch cluster at intervals of 10 seconds and stores the data to the indexes whose names start with .monitoring- in the cluster. In Elasticsearch V6.X clusters, the .monitoring-es-6-* and .monitoring-kibana-6-* indexes are used to store monitoring data. These indexes are rolled over every day. The name of a .monitoring-es-6-* index ends with the date when the monitoring data is stored.

A .monitoring-es-6-* index stores information such as the cluster status, cluster statistics, node statistics, and index statistics. Such indexes consume a large amount of disk space. For more information, see Configure monitoring indexes.

What encryption algorithm is used to encrypt disks for an Elasticsearch cluster?

Alibaba Cloud Elasticsearch uses the industry-standard AES-256 encryption algorithm and Key Management Service (KMS) to encrypt disks for Elasticsearch clusters. For more information, see Overview of disk encryption.

Is port 9300 supported by Elasticsearch clusters?

Only Elasticsearch V5.X clusters support port 9300 for TCP and port 9200 for HTTP and HTTPS. Elasticsearch clusters of other versions support only port 9200.

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