Handle Pre-Existing Data on the Destination

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Syntax

Command Option
Behavior
Steps
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Important

Cluster-to-Cluster Sync Beta Program

This feature is only available in mongosync beta. To learn more, see Cluster-to-Cluster Sync Beta Program.

Starting in mongosync beta 1.8, use the destinationDataHandling option in the start request to define what happens if the destination cluster already has user data. Earlier mongosync versions return an error if the destination cluster has user data.

Syntax

To set a "destinationDataHandling" option string:

curl <host>:<port>/api/v1/start -XPOST \
--data '
   {
      <options>,
      "destinationDataHandling": <string>
   } '

Command Option

The following table shows the strings you can set for "destinationDataHandling":

String	Description
`"requireEmptyDestination"`	`mongosync` requires databases on the destination cluster that you want to replicate from the source cluster are empty. `"requireEmptyDestination"` is the default.
`"ignorePreExistingNamespaces"`	`mongosync` ignores existing databases on the destination cluster. Ensure your destination namespaces are different from those `mongosync` replicates from the source cluster. `"ignorePreExistingNamespaces"` is not compatible with `reverse`.

If you omit a "destinationDataHandling" string, and the destination cluster has user data, mongosync returns an error. Otherwise, mongosync continues the sync operation.

Behavior

Verification

Destination Data Handling is not compatible with the Embedded Verifier. The /start command returns an error if you enable both the verifier and Destination Data Handling.

For more information, see Verify Data Transfer.

Steps

Connect the source and destination clusters

The following example connects a source cluster (cluster0) with a destination cluster (cluster1):

mongosync \
   --cluster0 "mongodb://localhost:27000" \
   --cluster1 "mongodb://localhost:35000"

Set the destinationDataHandling string

The following example sets "destinationDataHandling" to "ignorePreExistingNamespaces":

curl localhost:27182/api/v1/start -XPOST \
--data '
   {
      "source": "cluster0",
      "destination": "cluster1",
      "destinationDataHandling": "ignorePreExistingNamespaces"
   } '

The sync operation continues.

Learn More

Important

Cluster-to-Cluster Sync Beta Program

This feature is only available in mongosync beta. To learn more, see Cluster-to-Cluster Sync Beta Program.

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