Configure Additional Options¶

You can configure the following mongod runtime options on M10+ paid tier clusters.

To view these settings, open the More Configuration Options under Additional Settings in the cluster form.

Image showing more cluster configuration options.

Set Oplog Size¶

Modify the oplog size of the cluster.

For sharded cluster deployments, this modifies the oplog size of each shard in the cluster.

This option corresponds to modifying the replication.oplogSizeMB configuration file option for each mongod in the cluster.

Specify your desired Oplog Size in megabytes in the input box.

Important

If your change would reduce free disk space to below 25 percent, Atlas displays an error. Atlas doesn't change the oplog size until you choose a value above that threshold.

To check the oplog size:

Connect to your cluster via the mongo shell.
Authenticate as a user with the Atlas admin role.
Run the rs.printReplicationInfo() method.

Atlas displays the current oplog size and time.

Warning

Reducing the size of the oplog requires removing data from the oplog. Atlas cannot access or restore any oplog entries removed as a result of oplog reduction. Consider the ramifications of this data loss before reducing the oplog.

Disk Space Considerations¶

Do not reduce the size of the oplog as a means of increasing available disk space. Only the oplog collection (local.oplog.rs) can reclaim the space saved by reducing the oplog size. Other collections do not benefit from reducing oplog storage.

Enforce Index Key Limit¶

Enable or disable enforcement of the 1024-byte index key limit. Documents can only be updated or inserted if, for all indexed fields on the target collection, the corresponding index entries do not exceed 1024 bytes.

If disabled, mongod writes documents that breach the limit but does not index them. This option corresponds to modifying the failIndexKeyTooLong parameter via the setParameter command for each mongod in the cluster.

Important

Index Key Limit

failIndexKeyTooLong was deprecated in MongoDB version 4.2 and is removed in MongoDB 4.4 and later.

Allow Server-Side JavaScript¶

Enable or disable execution of operations that perform server-side execution of JavaScript.

If your cluster runs a MongoDB version less than 4.4, this option corresponds to modifying the security.javascriptEnabled configuration file option for each mongod in the cluster.
If your cluster runs MongoDB version 4.4 or greater, this option corresponds to modifying the security.javascriptEnabled configuration file option for each mongod and mongos in the cluster.

Note

In MongoDB version 4.4 and later, security.javascriptEnabled applies to mongos' as well.

Configure TLS Certificate Root¶

Atlas cluster TLS certificates use IdenTrust's root Certificate Authority (DST Root CA X3) by default until April 30, 2021. Beginning on May 1, 2021, new TLS certificates that MongoDB Atlas creates will use ISRG instead of IdenTrust for their root Certificate Authority in line with Let's Encrypt's announcement of this transition. All DST Root CA X3 expire on September 30, 2021.

If you wish to use ISRG instead of IdenTrust:

Select ISRG Root X1 from the drop-down.
Review changes to your cluster and click Apply Changes.
Atlas triggers a rolling restart of all the nodes in your cluster after 45 minutes when you switch between certificate roots. You can verify the change after the cluster restarts.
(Optional) Run the following command to verify the change:
```
echo | openssl s_client -showcerts -connect ${HOSTNAME}:${PORT} \
2> /dev/null | grep -E "(Certificate|CN\s*=|O\s*=)"
```
Set $HOSTNAME to a node hostname and $PORT to the port used to connect to MongoDB (usually 27017 or 27016). If you use Private Link to connect to your cluster, verify your cluster's port.

You can revert to DST if ISRG Root X1 causes any issues.

Note

If you switch certificate root for a shared-tier cluster, Atlas applies the change to all shared-tier clusters in the same project.

Set Minimum TLS Protocol Version¶

Sets the minimum TLS version the cluster accepts for incoming connections. This option corresponds to configuring the net.ssl.disabledProtocols configuration file option for each mongod in the cluster.

Note

TLS 1.0 Deprecation

For users considering this option as a method for enabling the deprecated Transport Layer Security (TLS) 1.0 protocol version, please read What versions of TLS does Atlas support? before proceeding. Atlas deprecation of TLS 1.0 improves your security of data-in-transit and aligns with industry best practices. Enabling TLS 1.0 for any Atlas cluster carries security risks. Consider enabling TLS 1.0 only for as long as required to update your application stack to support TLS 1.1 or later.

Require Indexes for All Queries¶

Enable or disable the execution of queries that require a collection scan to return results. This option corresponds to modifying the notablescan parameter via the setParameter command for each mongod in the cluster.

Considerations¶

Atlas dynamically modifies the Oplog Size for replica sets and sharded clusters. However, for the Minimum TLS Protocol Version and Allow Server-Side JavaScript settings, it performs a rolling restart of the shard members and the config server replica set. To learn more about how Atlas supports high availability during maintenance operations, see How does MongoDB Atlas deliver high availability?.

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