trove-specs/specs/liberty/percona-cluster.rst

Implement Percona cluster provisioning

To continue the Trove HA story, high availability of database instances is required in order to give users a peace of mind when running their production workloads in Trove. Apart from replication, clustering makes the deployment to be highly available by allowing data to be accessed from any node in the cluster. It enhances system uptime, it prevents from data loss and makes the architecture more scalable for future growth. Trove Clustering for the Percona datastore will be based on the Percona XtraDB Cluster, which is a true Multimaster Cluster based on synchronous replication.

This change will focus on the Create, List, Show, and Delete of a Peronca cluster. Grow and shrink of the cluster will be handled in a separate blueprint.

https://blueprints.launchpad.net/trove/+spec/support-pxc-56

Problem Description

The Percona datastore does not have support for clustering. Adding a cluster implementation will allow users to create read and write scalable and highly available deployments.

Proposed Change

Percona cluster will leverage the base cluster implementation that currently exists in Trove by creating plugabble and configurable strategies.

Requirements:

• The cluster should not have less than three nodes.
• Initial cluster creation will start with 3 or more.
• The cluster will return all IPs of its nodes. This is done so that the cluster can be used for multi write and read.
• The name of each instance will be automatically generated; it will be the <cluster_name>-<instance_num>.
• The clusters shall have nodes of same volumes but not for flavors.
• Clusters shall allow the instances/cluster members to be resizable for volume and flavors. No validation will occur if a user resizes volumes or flavors of an instance.

The following will be changed:

• A percona-cluster implementation will be added to common/strategies/cluster/experimental/mysql/xtradbcluster
• Task manager strategy to handle the cluster provisioning for percona.
• Guestagent strategy to handle the clustering provisioning, configuration and execution.
• Unit and integration tests.

Configuration

A new datastore configuration section will be added. This initial implementation will add no Percona-Cluster specific configuration options.

Trove Integration

The Redstack script will create a datastore configuration for percona-cluster to open ports 3306, 4444, 4567, and 4568.

Elements will be added to support "redstack kick-start percona-cluster-5.6".

Database

This implementation will leverage the existing database schema for cluster.

Public API

The API request for creating/deleting cluster will remain unchanged. However, there will be subtle differences in the response. Percona clustering will return all IPs of its nodes. This will be used for the user who wants to scale read/write.

Create Cluster

Request:

POST /v1.0/<tenant_id>/clusters
{
  "cluster": {
    "name": "products",
    "datastore": {
      "type": "percona",
      "version": "5.5"
    },
    "instances": [
      {
        "flavorRef": "2",
        "volume": {
          "size": 100
        },
      },
      {
        "flavorRef": "2",
        "volume": {
          "size": 100
        },
      },
      {
        "flavorRef": "2",
        "volume": {
          "size": 100
        },
      }
    ],
  }
}

Response:

{
  "cluster": {
    "id": "dfbbd9ca-b5e1-4028-adb7-f78643e17998",
    "task": {
      "id": 2,
      "name": "BUILDING",
      "description": "Building the initial cluster."
    },
    "name": "products",
    "created": "2014-04-25T20:19:23",
    "updated": "2014-04-25T20:19:23",
    "links": [{...}],
    "datastore": {
      "type": "percona",
      "version": "5.5"
    },
    "instances": [
      {
        "id": "416b0b16-ba55-4302-bbd3-ff566032e1c1",
        "status": "BUILD",
        "flavor": {
          "id": "2",
          "links": [{...}]
        },
        "volume": {
          "size": 100
        },
      },
      {
        "id": "965ef811-7c1d-47fc-89f2-a89dfdd23ef2",
        "status": "BUILD",
        "flavor": {
          "id": "2",
          "links": [{...}]
        },
        "volume": {
          "size": 100
        },
      },
      {
        "id": "3642f41c-e8ad-4164-a089-3891bf7f2d2b",
        "status": "BUILD",
        "flavor": {
          "id": "2",
          "links": [{...}]
        },
        "volume": {
          "size": 100
        },
      }
    ],
  }
}

Show Cluster

Request:

GET /v1.0/<tenant_id>/clusters/dfbbd9ca-b5e1-4028-adb7-f78643e17998

Response:

{
  "cluster": {
    "id": "dfbbd9ca-b5e1-4028-adb7-f78643e17998",
    "task": {
      "id": 1,
      "name": "NONE",
      "description": "No tasks for the cluster."
    },
    "name": "products",
    "created": "2014-04-25T20:19:23",
    "updated": "2014-04-25T20:19:23",
    "links": [{...}],
    "datastore": {
      "type": "percona",
      "version": "5.5"
    },
    "instances": [
      {
        "id": "416b0b16-ba55-4302-bbd3-ff566032e1c1",
        "status": "ACTIVE",
        "flavor": {
          "id": "7",
          "links": [{...}]
        },
        "volume": {
          "size": 100
        },
        "ip": "10.0.0.1"
      }
      {
        "id": "965ef811-7c1d-47fc-89f2-a89dfdd23ef2",
        "status": "ACTIVE",
        "flavor": {
          "id": "7",
          "links": [{...}]
        },
        "volume": {
          "size": 100
        },
        "ip": "10.0.0.2"
      },
      {
        "id": "3642f41c-e8ad-4164-a089-3891bf7f2d2b",
        "status": "BUILD",
        "flavor": {
          "id": "7",
          "links": [{...}]
        },
        "volume": {
          "size": 100
        },
        "ip": "10.0.0.3"
      }
    ],
  }
}

Show Instance

Request:

GET /v1.0/<tenant_id>/clusters/dfbbd9ca-b5e1-4028-adb7-f78643e17998/instances/416b0b16-ba55-4302-bbd3-ff566032e1c1

Response:

{
  "instance": {
    "status": "ACTIVE",
    "id": "416b0b16-ba55-4302-bbd3-ff566032e1c1",
    "cluster_id": "dfbbd9ca-b5e1-4028-adb7-f78643e17998",
    "name": "products-1",
    "created": "2014-04-25T20:19:23",
    "updated": "2014-04-25T20:19:23",
    "links": [{...}],
    "datastore": {
      "type": "percona",
      "version": "5.5"
    },
    "ip": ["10.0.0.1"],
    "flavor": {
      "id": "7",
      "links": [{...}],
    },
    "volume": {
      "size": 100,
      "used": 0.17
    },
  }
}

List Clusters

Request:

GET /v1.0/<tenant_id>/clusters

Response:

{
  "clusters": [
    {
      "id": "dfbbd9ca-b5e1-4028-adb7-f78643e17998",
      "task": {
        "id": 1,
        "name": "NONE",
        "description": "No tasks for the cluster."
      },
      "name": "products",
      "created": "2014-04-25T20:19:23",
      "updated": "2014-04-25T20:19:23",
      "links": [{...}],
      "ip": ["10.0.0.1", "10.0.0.2", "10.0.0.3"],
      "datastore": {
        "type": "percona",
        "version": "5.5"
      },
      "instances": [
        {
          "id": "416b0b16-ba55-4302-bbd3-ff566032e1c1",
          "status": "ACTIVE",
          "flavor": {
            "id": "7",
            "links": [{...}]
          },
          "volume": {
            "size": 100
          },
          "ip": "10.0.0.1",
        }
        {
          "id": "965ef811-7c1d-47fc-89f2-a89dfdd23ef2",
          "status": "ACTIVE",
          "flavor": {
            "id": "7",
            "links": [{...}]
          },
          "volume": {
            "size": 100
          },
          "ip": "10.0.0.2",
        },
        {
          "id": "3642f41c-e8ad-4164-a089-3891bf7f2d2b",
          "status": "ACTIVE",
          "flavor": {
            "id": "7",
            "links": [{...}]
          },
          "volume": {
            "size": 100
          },
          "ip": "10.0.0.3",
        }
      ]
    },
    ...
  ]
}

Delete Cluster

Request:

DELETE /v1.0/<tenant_id>/clusters/dfbbd9ca-b5e1-4028-adb7-f78643e17998

Response:

HTTP 202 (Empty Body)

Public API Security

None

Internal API

No changes in the internal API yet.

Guest Agent

No API changes in the guest agent. This feature will just be adding a new strategy to support a different type of clustering.

CLI (python-troveclient)

The following illustrates the clustering CLI

Create Cluster

$ trove help cluster-create

usage: trove cluster-create <name> <datastore> <datastore_version>
                            [--instance <instance>]

Creates a new cluster.

Positional arguments:
  <name>                Name of the cluster.
  <datastore>           A datastore name or UUID.
  <datastore_version>   A datastore version name or UUID.

Optional arguments:

  --instance <flavor_id=flavor_id,volume=volume,parameters=<key=value>>
                        Create an instance for the cluster. Specify
                        multiple times to create multiple instances.

Request:

$ trove cluster-create products percona "5.5" \
  --instance flavor_id=7,volume=2 \
  --instance flavor_id=7,volume=2 \
  --instance flavor_id=7,volume=2

Response:

+-------------------+--------------------------------------+
| Property          | Value                                |
+-------------------+--------------------------------------+
| created           | 2014-08-16T01:46:51                  |
| datastore         | percona                              |
| datastore_version | 5.5                                  |
| id                | aa6ef0f5-dbef-48cd-8952-573ad881e717 |
| name              | products                             |
| task_description  | Building the initial cluster.        |
| task_name         | BUILDING                             |
| updated           | 2014-08-16T01:46:51                  |
+-------------------+--------------------------------------+

The cluster-create command will create a cluster of functionally equivalent trove instances. Trove will choose a instance to start with the --wsrep-new-cluster option, then the remaining instances will be started sequentially. The cluster will be marked ACTIVE when all instances have started and the database is available for use.

Show Cluster

$ trove help cluster-show

usage: trove cluster-show <cluster>

Shows details of a cluster.

Positional arguments:
  <cluster>  ID or name of the cluster.

Request:

$ trove cluster-show aa6ef0f5-dbef-48cd-8952-573ad881e717

Response:

+-------------------+--------------------------------------+
| Property          | Value                                |
+-------------------+--------------------------------------+
| created           | 2014-08-16T01:46:51                  |
| datastore         | percona                              |
| datastore_version | 5.5                                  |
| id                | aa6ef0f5-dbef-48cd-8952-573ad881e717 |
| ip                | 10.0.0.2, 10.0.0.1, 10.0.0.3         |
| name              | products                             |
| task_description  | No tasks for the cluster.            |
| task_name         | NONE                                 |
| updated           | 2014-08-16T01:59:33                  |
+-------------------+--------------------------------------+

Show Cluster Instance

$ trove help cluster-instances

usage: trove cluster-instances <cluster>

Lists all instances of a cluster.

Positional arguments:
  <cluster>  ID or name of the cluster.

Request:

$ trove cluster-instances aa6ef0f5-dbef-48cd-8952-573ad881e717

Response:

+-------------------------------------+----------------+-----------+------+
| ID                                  | Name           | Flavor ID | Size |
+-------------------------------------+----------------+-----------+------+
| 45532fc4-661c-4030-8ca4-18f02a2b337 | products-1     | 7         |    2 |
| 7458a98d-6f89-4dfd-bb61-5cf1d65c121 | products-2     | 8         |    2 |
| 1557208f-5c23-4537-a9f2-52a9db38d3a | products-3     | 7         |    2 |
+-------------------------------------+----------------+-----------+------+

List Clusters

$ trove help cluster-list

usage: trove cluster-list [--limit <limit>] [--marker <ID>]

Lists all the clusters.

Optional arguments:
  --limit <limit>  Limit the number of results displayed.
  --marker <ID>    Begin displaying the results for IDs greater than the
                   specified marker. When used with --limit, set this to
                   the last ID displayed in the previous run.

Request:

$ trove cluster-list

Response:

+--------+----------+-----------+-----------+----------+-----------+
| ID     | Name     | Datastore | DsVersion | IP       | Task Name |
+--------+----------+-----------+-----------+----------+-----------+
| uuid-1 | products | percona   | 5.5       | ip1      | NONE      |
| uuid-2 | items    | percona   | 5.5       | ip2, ip3 | BUILDING  |
+--------+----------+-----------+-----------+----------+-----------+

Delete Cluster

$ trove help cluster-delete

usage: trove cluster-delete <cluster>

Deletes a cluster.

Positional arguments:
  <cluster>  ID of the cluster.

Request:

$ trove cluster-delete aa6ef0f5-dbef-48cd-8952-573ad881e717

Response:

(None)

Replication Impact

Due to the scope of adding a replica to a cluster this will be disabled as part of this blueprint and added as a separate blueprint.¹

Python API

???

Alternatives

None defined yet.

Upgrade Implications

To enable MySQL cluster support, a different package will be needed to install on the guest instance rather than the default. There are 2 ways to mitigate this in an upgrade path.

1. Update the packages installed on the datastore version.
2. Build a new image with the new package installed into the guest image.

Implementation

Assignee(s)

+---------------+--------------+---------+--------------------+ + Name + Launchpad Id + IRC + Email + +===============+==============+=========+====================+ + Steve Leon + steve-leon + esmute + kokhang@gmail.com + +---------------+--------------+---------+--------------------+ + Morgan Jones + 6-morgan + vgnbkr + morgan@tesora.com + +---------------+--------------+---------+--------------------+ + Craig Vyvial + cp16net + cp16net + cp16net@gmail.com + +---------------+--------------+---------+--------------------+

Milestones

Liberty-3

Work Items

• trove-integration change to add percona-xtradb-cluster-server package
• API strategy implementation
• Taskmanager strategy implementation
• Guestagent strategy implementation
• Unit and integration tests

Dependencies

None

Testing

There will be unit tests that test every components in the strategies. There will be integration tests which will test end-to-end cluster features

Documentation Impact

The response API will look different due to the nature of XtraDB clusters. For example, the view will contain all the IPs of the instances.

References

API strategy to handle clustering request for Percona. Besides the existing API, there will be new API to grow/shrink cluster handled in another blueprint. (bp/cluster-scaling² )

Trove does not monitor the status of cluster instances. Should an instance in the cluster become detached from the primary instance it will be up to the user to detect the situation and take corrective action. If the instance does not re-attach to the cluster in a state where an Incremental State Transfer (IST) is possible, it is suggested to delete the instance and add a new node to the cluster. (In the future, a user will be able to delete the instance from a cluster via the shrink action and add a new instance to the cluster with the grow action.)

In the event of a nova compute reboot, the nodes will automatically restart, and the cluster will automatically recover provided that the nodes can determine that the PRIMARY component can be properly recovered. In the case that the PRIMARY component cannot be recovered, operator intervention would be required to manually restart the cluster.

List of other cluster related blueprints. These blueprints will likely cause conflicts with changes.

---

1. percona-xtradb-with-replica: https://blueprints.launchpad.net/trove/+spec/percona-add-replica-of-cluster↩︎

2. bp/cluster-scaling: https://blueprints.launchpad.net/trove/+spec/cluster-scaling↩︎