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Connect Two Atlas Clusters

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  • Connection Strings
  • Authentication
  • Roles
  • Behavior
  • Example

The mongosync utility creates a connection between MongoDB clusters. mongosync can make a connection between:

  • self-managed clusters,

  • MongoDB Atlas hosted clusters, or

  • a self-managed cluster and an Atlas hosted cluster.

This page provides instructions to connect Atlas clusters using MongoDB Cluster-to-Cluster Sync. For additional details on connecting to an Atlas cluster, see Connect to a Database Deployment

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]

    For information on how to find your SRV connection string in Atlas, see Connect to Your Cluster.

  • 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 cluster. For more information, see Read Preference Options.

Authentication

Provide valid authentication to connect to a MongoDB Atlas cluster. If you do not already have an Atlas database user, you must create a user.

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 Atlas permissions are:

Sync Type
Target
Required Permissions
default
source cluster

  • atlasAdmin

  • backup

default
destination cluster

  • atlasAdmin

write-blocking or reversing
source cluster

  • atlasAdmin

  • backup

  • bypassWriteBlockMode privilege

write-blocking or reversing
destination cluster

  • atlasAdmin

  • backup

  • bypassWriteBlockMode privilege

For details on Atlas roles, see: Atlas User Roles.

To update Atlas user permissions, see: Manage Access to a Project.

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.

Limitations

Before you attempt to run mongosync with an M10+ Atlas cluster, disable the Require Indexes for All Queries option.

Example

Gather Connection Information

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

  • clusterOne-shard-00-00.abc12.mongodb.net:27017

  • clusterOne-shard-00-01.abc12.mongodb.net:27017

  • clusterOne-shard-00-02.abc12.mongodb.net:27017

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

  • clusterTwo-shard-00-00.abc12.mongodb.net:27017

  • clusterTwo-shard-00-01.abc12.mongodb.net:27017

  • clusterTwo-shard-00-02.abc12.mongodb.net:27017

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

Connect the Source and Destination Clusters with mongosync

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

cluster0:
mongodb+srv://clusterAdmin:superSecret@clusterOne.abc12.mongodb.net
cluster1:
mongodb+srv://clusterAdmin:superSecret@clusterTwo.abc12.mongodb.net

Note

Atlas clusters require TLS connections. To use mongosync with Atlas clusters, add the tls=true option or use the mongodb+srv connection string format. For more details about mongodb+srv connection strings, see SRV Connection Format.

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+srv://clusterAdmin:superSecret@clusterOne.abc12.mongodb.net" \
      --cluster1 "mongodb+srv://clusterAdmin:superSecret@clusterTwo.abc12.mongodb.net"
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