Create a Reference

To perform Cross Datacenter Replication (XDCR), you start by creating a reference to the remote cluster and bucket that will receive the replicated data.

Understanding References

A reference is the registration, on the local cluster, of details that identify a remote cluster as a suitable target for XDCR replication. The registration must contain the following details:

  • The name of the remote cluster.

  • The IP address or hostname of a node within the remote cluster.

  • A username and password, associated on the remote cluster with a role that provides XDCR management-privileges. The possible roles are Full, Cluster, and XDCR Administrator. Note that the administrator setting up XDCR must also have one of these roles on the local cluster.

  • Whether the the connection between source and target clusters will be managed securely, and if so, by what secure methodology. Corresponding TLS certificates may need to be provided. Securing a connection is described in detail in Secure a Replication.

Once the reference has been saved, it can be used to specify a target cluster, when an XDCR replication is created.

Examples on This Page

The examples in the subsections below show how to create the same reference; using the UI, the CLI, and the REST API respectively. The examples assume:

  • Two clusters already exist; each containing a single node. These are named after their IP addresses: 10.142.180.101 and 10.142.180.102.

  • Each cluster contains a single bucket, which is the travel-sample bucket. To access and install this, see Sample Buckets.

  • Each cluster has the Full Administrator username of Administrator, and password of password.

Choosing a Target Bucket

Since XDCR requires specification of a bucket on the target cluster, to which data is to be replicated, prior to creating a reference to a target cluster, you must know either:

  • The name of the existing target bucket to which data will be replicated

  • That you have the ability to create a target bucket to which data will be replicated.

The examples on this page use the travel-sample bucket, whose installation is described in Sample Buckets. For information on listing and creating additional buckets, see Manage Buckets.

Create an XDCR Reference with the UI

Proceed as follows:

  1. Access Couchbase Web Console. Left-click on the XDCR tab, in the right-hand navigation menu.

    left click on xdcr tab

    This displays the XDCR Replications screen:

    xdcr replications screen initial

    The lower part of the main panel is entitled Remote Clusters. The list, which is designed to show the name and IP address or hostname of each registered remote cluster, is currently empty, and so bears the notification No cluster references defined.

  2. Define a reference, by left-clicking on the Add Remote Cluster button, at the upper right.

    xdcr add remote cluster button

    The Add Remote Cluster dialog is now displayed:

    xdcr add remote cluster dialog

    The fields in this dialog are explained above, in Understanding References.

  3. For Cluster Name and IP/Hostname, specify the IP address of the second cluster, which is 10.142.180.102. For Username and Password, specify those stated above. Do not, for the current example, check the Enable Secure Connection checkbox. The complete dialog appears as follows:

    xdcr add remote cluster dialog complete

    When you have entered the data, left-click on the Save button.

    The XDCR Replications screen is again displayed. The Remote Clusters panel now contains the reference you have defined.

    xdcr replications screen with reference

This concludes reference-definition.

Editing and Deleting References with the UI

By left-clicking on the Edit and Delete options, provided on the row for each defined reference, you can respectively edit (by means of the Edit Remote Cluster dialog, which is identical to the Add Remote Cluster dialog) and delete defined references. Note that if a reference is already associated with a replication, you cannot delete the reference; nor can you modify its target IP address. However, you can change the registered name of the target cluster, and you can change the security settings for the replication.

Create an XDCR Reference with the CLI

Starting from the scenario defined above, in Examples on This Page, use the CLI xdcr-setup command to create an XDCR reference, as follows:

couchbase-cli xdcr-setup -c 10.142.180.101 -u Administrator \
 -p password \
--create \
--xdcr-cluster-name 10.142.180.102 \
--xdcr-hostname 10.142.180.102 \
--xdcr-username Administrator \
--xdcr-password password

If successful, this provides the following response:

SUCCESS: Cluster reference created

Note that a complete list of references established for a cluster can be retrieved with the xdcr-setup command, used with the list option:

couchbase-cli xdcr-setup -c 10.142.180.101 \
-u Administrator -p password --list

The following is returned. Note the uuid associated with the reference, which will be used later in the current section.

cluster name: 10.142.180.102
        uuid: 82026f90f5f573b5e50ec8b7a7012ab1
   host name: 10.142.180.102:8091
   user name: Administrator
         uri: /pools/default/remoteClusters/10.142.180.102

For more information, see the complete reference for the xdcr-setup command, which includes details on how to edit an existing reference.

Create an XDCR Reference with the REST API

Starting from the scenario defined above, in Examples on This Page, using the REST API’s POST /pools/default/remoteClusters HTTP method and URI, create an XDCR reference as follows:

curl -X  POST -u Administrator:password \
>  http://10.142.180.101:8091/pools/default/remoteClusters \
>  -d username=Administrator \
>  -d password=password \
>  -d hostname=10.142.180.102 \
>  -d name=10.142.180.102 \
>  -d demandEncryption=0

The output, if formatted, is as follows;

{
  "deleted": false,
  "hostname": "10.142.180.102:8091",
  "name": "10.142.180.102",
  "secureType": "none",
  "uri": "/pools/default/remoteClusters/10.142.180.102",
  "username": "Administrator",
  "uuid": "82026f90f5f573b5e50ec8b7a7012ab1",
  "validateURI": "/pools/default/remoteClusters/10.142.180.102?just_validate=1"
}

To return a list of the cluster’s current references, use the method as follows:

curl -i -X GET -u Administrator:password \
http://10.142.180.101:8091/pools/default/remoteClusters

Formatted, the output is as follows:

{
  "deleted": false,
  "hostname": "10.142.180.102:8091",
  "name": "10.142.180.102",
  "secureType": "none",
  "uri": "/pools/default/remoteClusters/10.142.180.102",
  "username": "Administrator",
  "uuid": "82026f90f5f573b5e50ec8b7a7012ab1",
  "validateURI": "/pools/default/remoteClusters/10.142.180.102?just_validate=1"
}

For more information on the REST APIs remoteClusters method, see the detailed reference pages on setting and getting references.

Next Steps

Once a reference to a target cluster has been defined, you can Create a Replication.