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Tribe node

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Tribe node

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The tribes feature allows a tribe node to act as a federated client across multiple clusters.

The tribe node works by retrieving the cluster state from all connected clusters and merging them into a global cluster state. With this information at hand, it is able to perform read and write operations against the nodes in all clusters as if they were local. Note that a tribe node needs to be able to connect to each single node in every configured cluster.

The elasticsearch.yml config file for a tribe node just needs to list the clusters that should be joined, for instance:

tribe:
    t1: 
        cluster.name:   cluster_one
    t2: 
        cluster.name:   cluster_two

t1 and t2 are arbitrary names representing the connection to each cluster.

The example above configures connections to two clusters, name t1 and t2 respectively. The tribe node will create a node client to connect each cluster using unicast discovery by default. Any other settings for the connection can be configured under tribe.{name}, just like the cluster.name in the example.

The merged global cluster state means that almost all operations work in the same way as a single cluster: distributed search, suggest, percolation, indexing, etc.

However, there are a few exceptions:

  • The merged view cannot handle indices with the same name in multiple clusters. By default it will pick one of them, see later for on_conflict options.
  • Master level read operations (eg Cluster State, Cluster Health) will automatically execute with a local flag set to true since there is no master.
  • Master level write operations (eg Create Index) are not allowed. These should be performed on a single cluster.

The tribe node can be configured to block all write operations and all metadata operations with:

tribe:
    blocks:
        write:    true
        metadata: true

The tribe node can also configure blocks on selected indices:

tribe:
    blocks:
        write.indices:    hk*,ldn*
        metadata.indices: hk*,ldn*

When there is a conflict and multiple clusters hold the same index, by default the tribe node will pick one of them. This can be configured using the tribe.on_conflict setting. It defaults to any, but can be set to drop (drop indices that have a conflict), or prefer_[tribeName] to prefer the index from a specific tribe.

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