Set up database replication

updated: 2019-10-26 10:22

Set up database replication¶

You can create a replica of an existing database instance. When you make subsequent changes to the original instance, the system automatically applies those changes to the replica.

Replicas are read-only.
When you create a replica, do not specify the --users or --databases options.
You can choose a smaller volume or flavor for a replica than for the original, but the replica’s volume must be big enough to hold the data snapshot from the original.

This example shows you how to replicate a MySQL database instance.

Set up replication¶

Get the instance ID

Get the ID of the original instance you want to replicate:

$ trove list
+-----------+------------+-----------+-------------------+--------+-----------+------+
|     id    |  name      | datastore | datastore_version | status | flavor_id | size |
+-----------+------------+-----------+-------------------+--------+-----------+------+
| 97b...ae6 | base_1     |   mysql   |     mysql-5.5     | ACTIVE |     10    |  2   |
+-----------+------------+-----------+-------------------+--------+-----------+------+

Create the replica

Create a new instance that will be a replica of the original instance. You do this by passing in the --replica_of option with the trove create command. This example creates a replica called replica_1. replica_1 is a replica of the original instance, base_1:
```
$ trove create replica_1 6 --size=5 --datastore_version mysql-5.5 \
  --datastore mysql --replica_of ID_OF_ORIGINAL_INSTANCE
```

Verify replication status

Pass in replica_1’s instance ID with the trove show command to verify that the newly created replica_1 instance is a replica of the original base_1. Note that the replica_of property is set to the ID of base_1.

$ trove show INSTANCE_ID_OF_REPLICA_1
+-------------------+--------------------------------------+
| Property          | Value                                |
+-------------------+--------------------------------------+
| created           | 2014-09-16T11:16:49                  |
| datastore         | mysql                                |
| datastore_version | mysql-5.5                            |
| flavor            | 6                                    |
| id                | 49c6eff6-ef91-4eff-91c0-efbda7e83c38 |
| name              | replica_1                            |
| replica_of        | 97b4b853-80f6-414f-ba6f-c6f455a79ae6 |
| status            | BUILD                                |
| updated           | 2014-09-16T11:16:49                  |
| volume            | 5                                    |
+-------------------+--------------------------------------+

Now pass in base_1’s instance ID with the trove show command to list the replica(s) associated with the original instance. Note that the replicas property is set to the ID of replica_1. If there are multiple replicas, they appear as a comma-separated list.

$ trove show INSTANCE_ID_OF_BASE_1
+-------------------+--------------------------------------+
| Property          | Value                                |
+-------------------+--------------------------------------+
| created           | 2014-09-16T11:04:56                  |
| datastore         | mysql                                |
| datastore_version | mysql-5.5                            |
| flavor            | 6                                    |
| id                | 97b4b853-80f6-414f-ba6f-c6f455a79ae6 |
| ip                | 172.16.200.2                         |
| name              | base_1                               |
| replicas          | 49c6eff6-ef91-4eff-91c0-efbda7e83c38 |
| status            | ACTIVE                               |
| updated           | 2014-09-16T11:05:06                  |
| volume            | 5                                    |
| volume_used       | 0.11                                 |
+-------------------+--------------------------------------+

Detach the replica

If the original instance goes down, you can detach the replica. The replica becomes a standalone database instance. You can then take the new standalone instance and create a new replica of that instance.

You detach a replica using the trove detach-replica command:
```
$ trove detach-replica INSTANCE_ID_OF_REPLICA
```

updated: 2019-10-26 10:22

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