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Connect Two Self-Managed Clusters

On this page

  • Connection Strings
  • Authentication
  • Roles
  • Behavior
  • Example

The mongosync utility creates a connection between MongoDB clusters. mongosync can connect to any of the following clusters:

  • self-managed clusters

  • MongoDB Atlas hosted clusters

  • a self-managed cluster and an Atlas hosted cluster

This page provides instructions to connect self-managed clusters using MongoDB Cluster-to-Cluster Sync.

Note

For best performance, upgrade your source and destination clusters to the most recent MongoDB Server patch release prior to migration. For more information, see Upgrade to the Latest Self-Managed Patch Release of MongoDB.

Connection Strings

mongosync uses a MongoDB URI connection string to connect clusters:

  • The SRV connection scheme has the form:

    mongodb+srv://[username:password@][host.domain.TLD][:port][/defaultauthdb][?options]

  • The standard URI connection scheme has the form:

    mongodb://[username:password@]host1[:port1][,...hostN[:portN]][/[defaultauthdb][?options]]

Specify the hostnames of the mongod instances the same way that they are listed in your replica set configuration.

For sharded clusters, specify the hostnames of the mongos instances instead of the mongod instances.

Note

mongosync does not require the replicaSet option.

mongosync requires the primary read preference to connect to the source and destination clusters. For more information, see Read Preference Options.

Authentication

If either the source or destination cluster requires authentication, you must give the correct credentials when calling mongosync.

Roles

The user specified in the mongosync connection string must have the required permissions on the source and destination clusters. The permissions vary depending on your environment and if you want to run a write-blocking or reverse sync.

The self-managed permissions are:

Sync Type
Required Source Permissions
Required Destination Permissions
Default
Write-blocking
Reversing

For details on server roles, see: Role-Based Access Control in Self-Managed Deployments.

To update user permissions, see: grantRolesToUser.

Behavior

Hosting

The mongosync utility can be hosted on its own hardware close to either the source or destination cluster. It does not have to be hosted on the same server as one of the mongod or mongos instances in the cluster. This flexibility allows you to push, or pull, data to the destination cluster with minimal impact on the mongod or mongos instances running there.

Initial State

When mongosync connects, it is in the IDLE state. You must issue the start command to begin syncing.

Example

Gather Connection Information

The source cluster, cluster0, is hosted on the following servers and ports:

  • clusterOne01.fancyCorp.com:20020

  • clusterOne02.fancyCorp.com:20020

  • clusterOne03.fancyCorp.com:20020

The destination cluster, cluster1, is hosted on the following servers and ports:

  • clusterTwo01.fancyCorp.com:20020

  • clusterTwo02.fancyCorp.com:20020

  • clusterTwo03.fancyCorp.com:20020

There is an administrative user, clusterAdmin configured on each cluster with password, superSecret.

Connect the Source and Destination Clusters with mongosync

The generic connection string format is:

mongodb://<user>:<password>@<ip-address>:<port>,<ip-address>:<port>,<ip-address>:<port>

Use the connection information you gathered to create the connection strings for cluster0 and cluster1:

cluster0:
mongodb://clusterAdmin:superSecret@clusterOne01.fancyCorp.com:20020,clusterOne02.fancyCorp.com:20020,clusterOne03.fancyCorp.com:20020
cluster1:
mongodb://clusterAdmin:superSecret@clusterTwo01.fancyCorp.com:20020,clusterTwo02.fancyCorp.com:20020,clusterTwo03.fancyCorp.com:20020

The mongosync command layout below is modified for display. To connect cluster0 to cluster1 with mongosync, enter the following command on one line:

mongosync \
      --cluster0 "mongodb://clusterAdmin:superSecret@clusterOne01.fancyCorp.com:20020,clusterOne02.fancyCorp.com:20020,clusterOne03.fancyCorp.com:20020" \
      --cluster1 "mongodb://clusterAdmin:superSecret@clusterTwo01.fancyCorp.com:20020,clusterTwo02.fancyCorp.com:20020,clusterTwo03.fancyCorp.com:20020"

You can also use mongodb+srv connection strings with mongosync. You do not need to add the tls=true option to a mongodb+srv connection string. For example:

mongosync \
   --cluster0 "mongodb+srv://clusterAdmin:superSecret@clusterOne01.fancyCorp.com/" \
   --cluster1 "mongodb+srv://clusterAdmin:superSecret@clusterTwo01.fancyCorp.com/"

For more details about mongodb+srv connection strings, see SRV Connection Format.

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