73 lines
2.8 KiB
Plaintext
73 lines
2.8 KiB
Plaintext
[[cluster-reroute]]
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== Cluster Reroute
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The reroute command allows to explicitly execute a cluster reroute
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allocation command including specific commands. For example, a shard can
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be moved from one node to another explicitly, an allocation can be
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canceled, or an unassigned shard can be explicitly allocated on a
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specific node.
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Here is a short example of how a simple reroute API call:
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[source,js]
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--------------------------------------------------
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curl -XPOST 'localhost:9200/_cluster/reroute' -d '{
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"commands" : [ {
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"move" :
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{
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"index" : "test", "shard" : 0,
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"from_node" : "node1", "to_node" : "node2"
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}
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},
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{
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"allocate" : {
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"index" : "test", "shard" : 1, "node" : "node3"
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}
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}
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]
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}'
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--------------------------------------------------
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An important aspect to remember is the fact that once when an allocation
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occurs, the cluster will aim at re-balancing its state back to an even
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state. For example, if the allocation includes moving a shard from
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`node1` to `node2`, in an `even` state, then another shard will be moved
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from `node2` to `node1` to even things out.
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The cluster can be set to disable allocations, which means that only the
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explicitly allocations will be performed. Obviously, only once all
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commands has been applied, the cluster will aim to be re-balance its
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state.
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Another option is to run the commands in `dry_run` (as a URI flag, or in
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the request body). This will cause the commands to apply to the current
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cluster state, and return the resulting cluster after the commands (and
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re-balancing) has been applied.
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If the `explain` parameter is specified, a detailed explanation of why the
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commands could or could not be executed is returned.
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The commands supported are:
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`move`::
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Move a started shard from one node to another node. Accepts
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`index` and `shard` for index name and shard number, `from_node` for the
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node to move the shard `from`, and `to_node` for the node to move the
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shard to.
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`cancel`::
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Cancel allocation of a shard (or recovery). Accepts `index`
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and `shard` for index name and shard number, and `node` for the node to
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cancel the shard allocation on. It also accepts `allow_primary` flag to
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explicitly specify that it is allowed to cancel allocation for a primary
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shard. This can be used to force resynchronization of existing replicas
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from the primary shard by cancelling them and allowing them to be
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reinitialized through the standard reallocation process.
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`allocate`::
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Allocate an unassigned shard to a node. Accepts the
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`index` and `shard` for index name and shard number, and `node` to
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allocate the shard to. It also accepts `allow_primary` flag to
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explicitly specify that it is allowed to explicitly allocate a primary
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shard (might result in data loss).
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