Cluster Scaling
Introduces new ReST API for cluster grow and cluster shrink. Also outlines changes to the python and CLI components to reflect the new operations. Change-Id: I6e2b8b1c96c2d5e667f5aaf7d017428805ce8136 Implements: blueprint cluster-scaling
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Morgan Jones
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specs/liberty/cluster-scaling.rst
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specs/liberty/cluster-scaling.rst
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..
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This work is licensed under a Creative Commons Attribution 3.0 Unported
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License.
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http://creativecommons.org/licenses/by/3.0/legalcode
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Sections of this template were taken directly from the Nova spec
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template at:
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https://github.com/openstack/nova-specs/blob/master/specs/template.rst
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===============
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Cluster Scaling
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===============
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Cluster support in trove currently has no direct support for growing
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or shrinking clusters. The current MongoDB cluster implementation
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does currently support adding a "shard" via the "add-shard" action,
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but it has been decided that this should be changed to use the new
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cluster-grow functionality outlined in this spec.
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The cluster-grow and cluster-shrink functionality has been discussed
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at the previous mid-cycle and summit, and it was accepted as a
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preferable alternative to the add-shard functionality currently
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implemented by the MongoDB datastore. This specification is intended
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to develop a foundation for the shrink/grow functionality in Percona
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and Redis clustering, and to be backward compatible with the MongoDB
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clustering implementation.
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Launchpad Blueprint:
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https://blueprints.launchpad.net/trove/+spec/cluster-scaling
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Problem Description
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===================
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Trove cluster support needs to be extended with support for increasing
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or decreasing the size of a cluster. This support will be provided by
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adding new ReST APIs for cluster-grow and cluster-shrink with
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corresponding CLI and python-troveclient support.
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The MongoDB cluster implementation will be enhanced to support
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cluster-grow in addition to the currently supported "add-shard"
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action.
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Proposed Change
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===============
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New ReST APIs
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-------------
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Two new ReST APIs will be added for this feature.
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cluster-grow
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////////////
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Adds nodes to a cluster.
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This new API adds 3 new attributes to the usual instance payload:
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:name: Name to assign to the instance
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:instance_type: Datastore specific type of the instance (eg.,
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query/replica for Mongo, master/slave for Redis).
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:related_to: Defines a relationship from one member to another. The
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value is datastore specific, but will likely refer to the
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name of a previously defined instance in the same ReST
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payload.
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Request::
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POST /v1.0/<tenant_id>/clusters/<cluster-id>/action
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{
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"grow": [
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{
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"name": "redis-clstr-member-5",
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"instance_type": "master",
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"flavorRef": "2",
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"volume": {
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"size": 2
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},
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},
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{
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"name": "redis-clstr-member-6",
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"instance_type": "slave",
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"related_to": "redis-clstr-member-5",
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"flavorRef": "2",
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"volume": {
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"size": 2
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},
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}
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]
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}
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Response::
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{
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"cluster": {
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"id": "edaac9ca-b5e1-4028-adb7-fa7653e11224",
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"task": {
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"id": 2,
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"name": "BUILDING",
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"description": "Building the initial cluster."
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},
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"name": "redis-clstr",
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"created": "2015-01-29T20:19:23",
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"updated": "2015-01-29T20:19:23",
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"links": [{...}],
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"datastore": {
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"type": "redis",
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"version": "3.0"
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},
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"ip": [],
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"instances": [
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{
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"id": "416b0b16-ba55-4302-bbd3-ff566032e1c1",
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"name": "redis-clstr-member-5",
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"instance_type": "master",
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"status": "BUILD",
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"ip": [],
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"links": [{...}],
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"flavor": {
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"id": "2",
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"links": [{...}]
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},
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"volume": {
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"size": 2
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}
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},
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{
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"id": "965ef811-7c1d-47fc-89f2-a89dfdd23ef2",
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"name": "redis-clstr-member-6",
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"instance_type": "slave",
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"related_to": "redis-clstr-member-5",
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"status": "BUILD",
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"ip": [],
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"links": [{...}],
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"flavor": {
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"id": "2",
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"links": [{...}]
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},
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"volume": {
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"size": 2
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}
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},
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]
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}
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}
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HTTP Codes::
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202 - Accepted.
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400 - BadRequest. Server could not understand request.
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403 - Forbidden. Local storage not specified in flavor ID: <ID>.
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403 - Forbidden. A flavor is required for each instance in the cluster.
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404 - Not Found. Flavor <id> not found.
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404 - Not Found. Cluster <id> not found.
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cluster-shrink
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//////////////
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Deletes the specified instances from the cluster.
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Request::
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POST /v1.0/<tenant_id>/clusters/<cluster_id>/action
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"shrink": [
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{
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"id": "416b0b16-ba55-4302-bbd3-ff566032e1c1",
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},
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{
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"id": "965ef811-7c1d-47fc-89f2-a89dfdd23ef2",
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}
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]
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}
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Response::
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N/A
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HTTP codes::
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202 - Accepted.
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403 - Forbidden. Instance <instance_id> not in state to be removed.
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404 - Instance <instance_id> not found in cluster <id>.
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Configuration
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-------------
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n/a
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Database
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--------
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n/a
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Public API
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----------
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This change adds new CLI commands cluster-grow and cluster-shrink,
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detailed below. These CLI commands and their corresponding APIs
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should be consistent with existing CLI and API usage.
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Public API Security
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-------------------
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No security impacts are expected.
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Python API
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----------
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The following methods will be added to the Clusters class in
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the python-troveclient::
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class Clusters:
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def grow(self, cluster, instances)
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"""Grow the specified cluster.
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:param cluster: The cluster to grow
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:param instances: JSON describing instances to add
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"""
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def shrink(self, cluster, instances)
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"""Shrink the specified cluster.
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:param cluster: The cluster to shrink
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:param instances: JSON describing instances to remove
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"""
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CLI (python-troveclient)
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------------------------
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cluster-grow
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////////////
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Basic Grow
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++++++++++
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Basic Grow would be suitable to databases such as Galera or Cassandra
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where all nodes are effectively peers - no special options are
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required.
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::
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$ trove cluster-grow mycluster --instance flavor=7
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<example output to follow>
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--instance parameter may be specified multiple times.
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Generated Request::
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POST /v1.0/<tenant_id>/clusters/<cluster-id>/action
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{
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"grow": [
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{
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"flavorRef": "7",
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}
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]
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}
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Add Master and Slave
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++++++++++++++++++++
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Master and Slave grow would be suitable for databases such as Redis
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which support master/slave replication within a cluster.
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::
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$ trove cluster-grow mycluster \
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--instance name=newnode1,type=master,flavor=7 \
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--instance name=newnode2,type=slave,related_to=newnode1,flavor=7
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Generated Request::
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POST /v1.0/<tenant_id>/clusters/<cluster-id>/action
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{
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"grow": [
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{
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"name": "newnode1",
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"instance_type": "master",
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"flavorRef": "7"
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},
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{
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"name": "newnode2",
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"instance_type": "slave",
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"related_to": "newnode1",
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"flavorRef": "7 "
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}
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]
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}
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To add a standby node to a node named "node1" in a database such as
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Vertica or Redis, a simpler form of the above could be used.
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::
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$ trove cluster-grow mycluster \
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--instance type=standby,related_to=node1,flavor=7
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Generated Request::
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POST /v1.0/<tenant_id>/clusters/<cluster-id>/action
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{
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"grow": [
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{
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"instance_type": "standby",
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"related_to": "node1",
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"flavorRef": "7 "
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}
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]
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}
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Add Replica Set
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+++++++++++++++
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This form of Grow Cluster would be used for databases such as MongoDB
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which implement growth by shards, in this case called "replica sets".
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The example below creates a new query server plus two replica sets of
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3 nodes each.
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::
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$ trove cluster-grow mycluster \
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--instance name=rs2q,type=query,flavor=7 \
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--instance name=rs2a,type=replica,flavor=7 \
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--instance name=rs2b,type=replica,related_to=rs2a,flavor=7 \
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--instance name=rs2c,type=replica,related_to=rs2b
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--instance name=rs3a,type=replica,flavor=7 \
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--instance name=rs3b,type=replica,related_to=rs3a,flavor=7 \
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--instance name=rs3c,type=replica,related_to=rs3b
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Generated Request::
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POST /v1.0/<tenant_id>/clusters/<cluster-id>/action
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{
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"grow": [
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{
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"name": "rs2q",
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"instance_type": "query",
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"flavorRef": "7"
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},
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{
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"name": "rs2a",
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"instance_type": "replica",
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"flavorRef": "7"
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},
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{
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"name": "rs2b",
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"instance_type": "replica",
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"related_to": "rs2a",
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"flavorRef": "7 "
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},
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{
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"name": "rs2c",
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"instance_type": "replica",
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"related_to": "rs2b",
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"flavorRef": "7 "
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},
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{
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"name": "rs3a",
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"instance_type": "replica",
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"flavorRef": "7"
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},
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{
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"name": "rs3b",
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"instance_type": "replica",
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"related_to": "rs3a",
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"flavorRef": "7 "
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},
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{
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"name": "rs3c",
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"instance_type": "replica",
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"related_to": "rs3b",
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"flavorRef": "7 "
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}
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]
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}
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cluster-shrink
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//////////////
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::
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$ trove cluster-shrink mycluster nodename-1 nodename-2
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<example output to follow>
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Internal API
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------------
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Appropriate methods will be added to the base Cluster Strategy.
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Guest Agent
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-----------
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Appropriate methods will be added to the base Cluster Strategy.
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The MongoDB Implementation will be adapted to support both the existing
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add-shard functionality, plus the new cluster-grow functionality.
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Alternatives
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------------
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n/a
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Implementation
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==============
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Assignee(s)
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-----------
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Primary assignee:
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Matthew Van Dijk
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Morgan Jones
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Milestones
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----------
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Target Milestone for completion:
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Liberty-3
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Work Items
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----------
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- Implement base cluster-shrink/cluster-grow functionality
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- Update MongoDB Clustering implementation to use new APIs
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Upgrade Implications
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====================
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The MongoDB clustering implementation will continue to support the
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existing "add-shard" functionality.
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Dependencies
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============
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n/a
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Testing
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=======
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int-tests for clustering functionality is still under consideration.
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Documentation Impact
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====================
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The new cluster-grow and cluster-shrink functionality will need to be
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documented.
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The MongoDB Datastore documentation will need to be updated to reflect
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Mongo's implementation of both the old and new functionality.
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References
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==========
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n/a
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