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mongosync Binary

Definition

The mongosync binary is the primary process used in Cluster-to-Cluster Sync. mongosync migrates data from a source cluster to a destination cluster and keeps the clusters in continuous sync until you finalize the sync. In addition to continuous data synchronization, mongosync can also perform a one time data migration between clusters.

For an overview of the mongosync process, see About mongosync.

To get started with mongosync, refer to the Quick Start Guide.

The Frequently Asked Questions (FAQ) page addresses questions users have asked about mongosync.

Compatibility

  • mongosync does not yet support migrations to and from clusters that use MongoDB 8.0. For instructions on migrating data to 8.0 destination clusters, see Synchronize Data From a Pre-8.0 Source Cluster to an 8.0 Destination Cluster and Synchronize Data Between Two 8.0 Clusters.

  • The minimum supported server versions of MongoDB are 6.0.16 and 7.0.9.

    You can migrate data on clusters (source) with versions of MongoDB lower than 6.0 to an Atlas cluster (destination). Migration from clusters with lower version requires additional preparation and configuration in the clusters with the lower version. Contact your account team to inquire about Professional Services.

  • mongosync supports replica sets and sharded clusters.

  • Standalone MongoDB instances are not supported. Convert the standalone instance to a replica set before using Cluster-to-Cluster Sync.

  • mongosync does not support Atlas shared clusters or serverless instances.

  • For a full list of limitations, see Cluster-to-Cluster Sync Limitations.

Syntax

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 "<cluster0_connection_string>" \
      --cluster1 "<cluster1_connection_string>"

For more information on how to format your connection strings, see Connecting mongosync.

Command Line Options

You can configure the following mongosync options using the command line.

To configure mongosync from a configuration file, see Configuration File.

Global Options

--cluster0 <uri>

Sets the connection URI for the first cluster. The first cluster can serve as either the source or the destination in the sync process. Designate the source and destination clusters in the call to the start API endpoint.

For more information on connecting mongosync, see Connections.

To set the --cluster0 option from a configuration file, see the cluster0 setting.

Warning

On some systems, providing a password in a connection string with the --cluster0 or --cluster1 options may make the password visible to system status programs, such as ps, that may be invoked by other users.

Consider using the --config option to specify a configuration file containing the password instead.

--cluster1 <uri>

Sets the connection URI for the second cluster. The second cluster can serve as either the source or the destination in the sync process. Designate the source and destination clusters in the call to the start API endpoint.

For more information on connecting mongosync, see Connections.

To set the --cluster1 option from a configuration file, see the cluster1 setting.

Warning

On some systems, providing a password in a connection string with the --cluster0 or --cluster1 options may make the password visible to system status programs, such as ps, that may be invoked by other users.

Consider using the --config option to specify a configuration file containing the password instead.

--config <filename>

Sets the path to the configuration file.

To set the configuration file path during a migration, see Reconfigure mongosync During Synchronization.

For more information, see Configuration File.

--disableTelemetry

New in version 1.4.0.

Disables the collection of telemetry data for mongosync.

By default, mongosync collects anonymous, aggregated usage data to improve MongoDB products. When you run mongosync you can disable collection of this telemetry data.

To set the --disableTelemetry option from a configuration file, see the disableTelemetry setting.

To disable telemetry data collection during a migration, see Reconfigure mongosync During Synchronization.

For more information, see User Data Collection.

--help, -h

Prints usage information to stdout.

--id <id>

Sets an identifier for the mongosync instance.

Use this option when running multiple instances of mongosync on a sharded cluster, to synchronize the shards individually.

The identifier value for this option must correspond to the shard ID of the shard it syncs. To find the shard ID, use the listShards command.

To set the --id option from a configuration file, see the id setting.

--loadLevel <level>

Type: integer

Default: 3

Sets the cluster workload level for syncing data between the source and destination clusters:

  • 4, the highest setting, maximizes cluster workload and syncs data the fastest.

  • 1, the lowest setting, minimizes cluster workload and syncs data the slowest.

To set the --loadLevel option from a configuration file, see the loadLevel setting.

To change the load level during a migration, see Reconfigure mongosync During Synchronization.

Warning

Setting loadLevel higher than the default of 3 may negatively impact the destination cluster performance.

New in version 1.4.

--logPath <directory>

Sets the path to the log directory. Cluster-to-Cluster Sync writes logs to files in this directory.

For more information, see Logging.

To set the --logPath option from a configuration file, see the logPath setting.

To change the path to the log directory during a migration, see Reconfigure mongosync During Synchronization.

Note

If you start mongosync with the --logPath option, you can send a USR1 signal to the mongosync process to rotate its log file:

kill -s USR1 $mongosync_pid

$mongosync_pid is the mongosync process ID.

--port

Default: 27182

Sets the port used by the HTTP server for the Cluster-to-Cluster Sync HTTP API.

To set the --port option from a configuration file, see the port setting.

To change the port during a migration, see Reconfigure mongosync During Synchronization.

--verbosity <level>

Default: DEBUG

Sets the verbosity level to use in log messages. Cluster-to-Cluster Sync logs all messages at the specified level and any messages at lower levels.

The --verbosity option supports the following values:

  • TRACE

  • DEBUG

  • INFO

  • WARN

  • ERROR

  • FATAL

  • PANIC

To set the --verbosity option from a configuration file, see the verbosity setting.

To change the verbosity level during a migration, see Reconfigure mongosync During Synchronization.

--version, -v

Prints mongosync version information to stdout.

Behavior

For more information, see mongosync Behavior.

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