Help Center/ Cloud Search Service/ User Guide/ Using Elasticsearch for Data Search/ Scaling an Elasticsearch Cluster/ Scaling Out an Elasticsearch Cluster
Updated on 2024-10-26 GMT+08:00
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Scaling Out an Elasticsearch Cluster

If the workloads on the data plane of an Elasticsearch or OpenSearch cluster increase, you can scale out the cluster by increasing the quantity or capacity of its nodes, including changing the node specifications and types.

Scenario

CSS supports multiple scale-out methods, as described in Table 1.

Table 1 Scaling out an Elasticsearch cluster

Scenario

Description

Details

Increasing the quantity and capacity of nodes

Only the quantity and storage capacity of nodes can be increased. Applicable scenarios:

  • If a data node (ess) is under heavy pressure and responds slowly, you can expand its storage capacity to improve its performance and storage reliability. If some nodes become unavailable due to excessively large data volumes or misoperations, you can add new nodes to ensure cluster availability.
  • Cold data nodes (ess-cold) are used to share the load of data nodes. To prevent the loss of cold data, you can expand the storage capacity of existing cold data nodes or add new ones.

Adding More Nodes and Increasing Node Storage Capacity

Increasing node specifications

You can only change the node specifications of a cluster by node type. Applicable scenarios:

  • If the allocation of new indexes or shards takes too long or the coordination and scheduling of nodes are inefficient, increase the master node (ess-master) specifications.
  • If too many requests need to be handled or too many results need to be aggregated, increase the client node (ess-client) specifications.
  • If data nodes (ess) are becoming slower in responding to data writing and query requests, increase the specifications of the data nodes.
  • If cold data query becomes slow, increase the cold node (ess-cold) specifications.

Changing the Node Specifications of an Elasticsearch Cluster

Adding new node types

For a cluster that has no master (ess-master) or client (ess-client) nodes, as the load on its data plane increases, you can add master or client nodes as needed to scale up capacity.

Adding Master or Client Nodes

Constraints

  • The node storage capacity of a cluster can only be increased but cannot be reduced. Select an appropriate node storage capacity based on the data volume and projected data growth.
  • The number of nodes and node storage capacity cannot be expanded at the same time for a yearly/monthly cluster.
  • In each cluster, the number of nodes supported by each node type varies, depending on the types of nodes used in that cluster. For details, see Table 2.
    Table 2 Number of nodes of different types allowed in a single cluster

    Node Type

    Node Quantity

    ess

    ess: 1-32

    ess, ess-master

    ess: 1-200

    ess-master: an odd number ranging from 3 to 9

    ess, ess-client

    ess: 1-32

    ess-client: 1-32

    ess, ess-cold

    ess: 1-32

    ess-cold: 1-32

    ess, ess-master, ess-client

    ess: 1-200

    ess-master: an odd number ranging from 3 to 9

    ess-client: 1-32

    ess, ess-master, ess-cold

    ess: 1-200

    ess-master: an odd number ranging from 3 to 9

    ess-cold: 1-32

    ess, ess-client, ess-cold

    ess: 1-32

    ess-client: 1-32

    ess-cold: 1-32

    ess, ess-master, ess-client, ess-cold

    ess: 1-200

    ess-master: an odd number ranging from 3 to 9

    ess-client: 1-32

    ess-cold: 1-32
    NOTE:
    • ess: data node, which is the default node type that is mandatory for cluster creation. The other three node types are optional.
    • ess-master: master node
    • ess-client: client node
    • ess-cold: cold data node

Prerequisites

  • The cluster is available and has no tasks in progress.
  • CSS has sufficient resources to expand cluster capacity.

Adding More Nodes and Increasing Node Storage Capacity

  1. Log in to the CSS management console.
  2. In the navigation pane, choose a cluster type. The cluster management page is displayed.
  3. Choose More > Modify Configuration in the Operation column of the target cluster. The Modify Configuration page is displayed.
  4. Click the Scale Cluster tab.
  5. Set the necessary parameters.
    Table 3 Adding more nodes or increasing node storage capacity

    Parameter

    Description

    Action

    Select Scale out.

    Resources

    Shows the change of resources for this scale-out operation.

    Nodes

    Increase the number of nodes and node storage capacity in the Nodes and Node Storage Type columns. You can change multiple node types at the same time.

    • For the value range of node quantity for each node type, see Table 2.
    • The value range of node storage capacity is determined by the node specifications. The value must be a multiple of 20.
    NOTE:

    The number of nodes and node storage capacity cannot be expanded at the same time for a yearly/monthly cluster.
    Figure 1 Scaling out a cluster
  6. Click Next.
  7. Confirm the information and click Submit.
  8. Click Back to Cluster List to switch to the Clusters page. The Task Status is Scaling out. When Cluster Status changes to Available, the cluster has been successfully scaled out.

Adding Master or Client Nodes

  1. Log in to the CSS management console.
  2. In the navigation pane, choose a cluster type. The cluster management page is displayed.
  3. In the cluster list, select the target cluster, and choose More > Modify Configuration in the Operation column. The Modify Configuration page is displayed.
  4. On the Modify Configuration page, choose the Add Master/Client Node tab.

    If a cluster already has both master and client nodes, the Add Master/Client Node tab is unavailable.

  5. Select the target node type and set the node specifications, quantity, and storage.
    Table 4 Adding master or client nodes

    Parameter

    Description

    Node types

    Select the type of nodes you want to add.

    • Only one node type can be selected at a time. If you need to add both Master and Client nodes, you need to perform this task twice.
    • If the cluster already has Master or Client nodes, only the other node type is displayed here.

    Node Specifications

    Select node specifications based on site requirements.

    Nodes

    Set the number of nodes to add for this node type. For the value range, see Table 2.

    Node Storage Type

    Set the node storage type and capacity. The value range of node storage capacity is determined by the node specifications. The value must be a multiple of 20.
    Figure 2 Adding master/client nodes
  6. Click Next.
  7. Confirm the information and click Submit.

    Return to the cluster list page. The Task Status of the cluster is Scaling out.

    • If you add a master node and Cluster Status changes to Available, the master node has been successfully added.

      If the cluster version is earlier than 7.x, when the Cluster Status changes to Available, you need to restart all data nodes and cold data nodes in the cluster to make the new node take effect. If the data nodes and cold data nodes are not restarted, the cluster may be reported as unavailable. (The cluster services still run properly.) For details, see Restarting an Elasticsearch Cluster.

    • If you add a client node and Cluster Status changes to Available, the client node has been added. You can restart data nodes and cold data nodes to shut down Cerebro and Kibana processes on these nodes.