Upgrade a Standalone to 4.4
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Warning
When upgrading a MongoDB 4.2-series deployment containing MongoDB 3.0 metadata to a 4.4-series deployment, you must upgrade to MongoDB 4.4.1 or later. You cannot successfully upgrade a deployment containing MongoDB 3.0 metadata to MongoDB 4.4.0 without serious risk of downtime.
For more information, see WT-6623.
Familiarize yourself with the content of this document, including thoroughly reviewing the prerequisites, prior to upgrading to MongoDB 4.4.
The following steps outline the procedure to upgrade a standalone
mongod from version 4.2 to 4.4.
If you need guidance on upgrading to 4.4, MongoDB professional services offer major version upgrade support to help ensure a smooth transition without interruption to your MongoDB application.
Upgrade Recommendations and Checklists
When upgrading, consider the following:
Upgrade Version Path
To upgrade an existing MongoDB deployment to 4.4, you must be running a 4.2-series release.
To upgrade from a version earlier than the 4.2-series, you must successively upgrade major releases until you have upgraded to 4.2-series. For example, if you are running a 4.0-series, you must upgrade first to 4.2 before you can upgrade to 4.4.
Check Driver Compatibility
Before you upgrade MongoDB, check that you're using a MongoDB 4.4-compatible driver. Consult the driver documentation for your specific driver to verify compatibility with MongoDB 4.4.
Upgraded deployments that run on incompatible drivers might encounter unexpected or undefined behavior.
Preparedness
Before beginning your upgrade, see the Compatibility Changes in MongoDB 4.4 document to ensure that your applications and deployments are compatible with MongoDB 4.4. Resolve the incompatibilities in your deployment before starting the upgrade.
Before upgrading MongoDB, always test your application in a staging environment before deploying the upgrade to your production environment.
Downgrade Consideration
Once upgraded to 4.4, if you need to downgrade, we recommend downgrading to the latest patch release of 4.2.
Warning
Downgrade Floor
If you need to downgrade from version 4.4, downgrade to 4.2.6 or a later version. You cannot downgrade to 4.2.5 or an earlier version.
Prerequisites
Confirm Clean Shutdown
Prior to upgrading, confirm that your mongod instance was
cleanly shut down.
Feature Compatibility Version
The 4.2 instance must have featureCompatibilityVersion set
to "4.2". To check featureCompatibilityVersion:
db.adminCommand( { getParameter: 1, featureCompatibilityVersion: 1 } )
The operation should return a result that includes
"featureCompatibilityVersion" : { "version" : "4.2" }.
To set or update featureCompatibilityVersion, run the following
command:
db.adminCommand( { setFeatureCompatibilityVersion: "4.2" } )
For more information, see setFeatureCompatibilityVersion.
Consider Converting to Replica Set
Prior to upgrading, consider converting your standalone deployment to a replica set. Replica sets are the recommended deployment configuration for MongoDB.
Download 4.4 Binaries
Via Package Manager
If you installed MongoDB from the MongoDB apt, yum, dnf, or
zypper repositories, you should upgrade to 4.4 using your package
manager.
Follow the appropriate 4.4 installation instructions for your Linux system. This will involve adding a repository for the new release, then performing the actual upgrade process.
Manually
If you have not installed MongoDB using a package manager, you can manually download the MongoDB binaries from the MongoDB Download Center.
See 4.4 installation instructions for more information.
Upgrade Process
Warning
If you upgrade an existing instance of MongoDB to MongoDB
4.4.19, that instance may fail to start if fork: true is
set in the mongod.conf file.
The upgrade issue affects all MongoDB instances that use .deb or
.rpm installation packages. Installations that use the tarball
(.tgz) release or other package types are not affected. For more
information, see SERVER-74345.
To remove the fork: true setting, run these commands from a system
terminal:
systemctl stop mongod.service sed -i.bak '/fork: true/d' /etc/mongod.conf systemctl start mongod.service
The second systemctl command starts the upgraded instance after the
setting is removed.
Enable backwards-incompatible 4.4 features.
At this point, you can run the 4.4 binaries without the 4.4 features that are incompatible with 4.2.
To enable these 4.4 features, set the feature compatibility
version (fCV) to 4.4.
Tip
Enabling these backwards-incompatible features can complicate the downgrade process since you must remove any persisted backwards-incompatible features before you downgrade.
It is recommended that after upgrading, you allow your deployment to run without enabling these features for a burn-in period to ensure the likelihood of downgrade is minimal. When you are confident that the likelihood of downgrade is minimal, enable these features.
Run the setFeatureCompatibilityVersion command against the admin database:
db.adminCommand( { setFeatureCompatibilityVersion: "4.4" } )
This command must perform writes to an internal system collection. If for any reason the command does not complete successfully, you can safely retry the command as the operation is idempotent.
Additional Upgrade Procedures
To upgrade a replica set, see Upgrade a Replica Set to 4.4.
To upgrade a sharded cluster, see Upgrade a Sharded Cluster to 4.4.