Upgrade MongoDB to 3.0¶
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In the general case, the upgrade from MongoDB 2.6 to 3.0 is a binary-compatible “drop-in” upgrade: shut down the mongod instances and replace them with mongod instances running 3.0. However, before you attempt any upgrade please familiarize yourself with the content of this document, particularly the procedure for upgrading sharded clusters.
If you need guidance on upgrading to 3.0, MongoDB offers consulting to help ensure a smooth transition without interruption to your MongoDB application.
Upgrade Recommendations and Checklists¶
When upgrading, consider the following:
To upgrade an existing MongoDB deployment to 3.0, you must be running 2.6. If you’re running a version of MongoDB before 2.6, you must upgrade to 2.6 before upgrading to 3.0. See Upgrade MongoDB to 2.6 for the procedure to upgrade from 2.4 to 2.6. Once upgraded to MongoDB 2.6, you cannot downgrade to any version earlier than MongoDB 2.4.
If your existing MongoDB deployment is already running with authentication and authorization, your user data model authSchema must be at least version 3. To verify the version of your existing authSchema, see MongoDB 2.4 User Model Removed. To upgrade your authSchema version, see Upgrade User Authorization Data to 2.6 Format for details.
Before upgrading MongoDB, always test your application in a staging environment before deploying the upgrade to your production environment.
Some changes in MongoDB 3.0 require manual checks and intervention. Before beginning your upgrade, see the Compatibility Changes in MongoDB 3.0 document to ensure that your applications and deployments are compatible with MongoDB 3.0. Resolve the incompatibilities in your deployment before starting the upgrade.
Once upgraded to MongoDB 3.0, you cannot downgrade to a version lower than 2.6.8.
If you upgrade to 3.0 and have run authSchemaUpgrade, you cannot downgrade to 2.6 without disabling --auth or restoring a pre-upgrade backup, as authSchemaUpgrade discards the MONGODB-CR credentials used in 2.6. See Upgrade Existing MONGODB-CR Users to Use SCRAM-SHA-1.
Upgrade MongoDB Processes¶
Upgrade Standalone mongod Instance to MongoDB 3.0¶
The following steps outline the procedure to upgrade a standalone mongod from version 2.6 to 3.0. To upgrade from version 2.4 to 3.0, upgrade to version 2.6 first, and then use the following procedure to upgrade from 2.6 to 3.0.
If you installed MongoDB from the MongoDB apt, yum, or zypper repositories, you should upgrade to 3.0 using your package manager. Follow the appropriate installation instructions for your Linux system. This will involve adding a repository for the new release, then performing the actual upgrade.
Otherwise, you can manually upgrade MongoDB:
Upgrade a Replica Set to 3.0¶
- If the oplog contains entries generated by versions of MongoDB that precede version 2.2.1, you must wait for the entries to be overwritten by later versions before you can upgrade to MongoDB 3.0. For more information, see Replica Set Oplog Format Change
- Stricter validation in MongoDB 3.0 of replica set configuration may invalidate previously-valid replica set configuration, preventing replica sets from starting in MongoDB 3.0. For more information, see Replica Set Configuration Validation.
- All replica set members must be running version 2.6 before you can upgrade them to version 3.0. To upgrade a replica set from an earlier MongoDB version, upgrade all members of the replica set to version 2.6 first, and then follow the procedure to upgrade from MongoDB 2.6 to 3.0.
You can upgrade from MongoDB 2.6 to 3.0 using a “rolling” upgrade to minimize downtime by upgrading the members individually while the other members are available:
Upgrade secondary members of the replica set.¶
Upgrade the secondary members of the set one at a time by shutting down the mongod and replacing the 2.6 binary with the 3.0 binary. After upgrading a mongod instance, wait for the member to recover to SECONDARY state before upgrading the next instance. To check the member’s state, issue rs.status() in the mongo shell.
Replica set failover is not instant and will render the set unavailable to accept writes until the failover process completes. This may take 30 seconds or more: schedule the upgrade procedure during a scheduled maintenance window.
Upgrade a Sharded Cluster to 3.0¶
Only upgrade sharded clusters to 3.0 if all members of the cluster are currently running instances of 2.6. The only supported upgrade path for sharded clusters running 2.4 is via 2.6. The upgrade process checks all components of the cluster and will produce warnings if any component is running version 2.4.
The upgrade process does not require any downtime. However, while you upgrade the sharded cluster, ensure that clients do not make changes to the collection meta-data. For example, during the upgrade, do not do any of the following:
- any operation that creates a database
- any other operation that modifies the cluster metadata in any way. See Sharding Reference for a complete list of sharding commands. Note, however, that not all commands on the Sharding Reference page modifies the cluster meta-data.
Upgrade Sharded Clusters¶
Optional but Recommended. As a precaution, take a backup of the config database before upgrading the sharded cluster.
Upgrade the cluster’s meta data.¶
To run a mongos with the --upgrade option, you can upgrade an existing mongos instance to 3.0, or if you need to avoid reconfiguring a production mongos instance, you can use a new 3.0 mongos that can reach all the config servers.
To upgrade the meta data, run:
mongos --configdb <configDB string> --upgrade
You can include the --logpath option to output the log messages to a file instead of the standard output. Also include any other options required to start mongos instances in your cluster, such as --sslOnNormalPorts or --sslPEMKeyFile.
The 3.0 mongos will output informational log messages.
<timestamp> I SHARDING [mongosMain] MongoS version 3.0.0 starting: ... ... <timestamp> I SHARDING [mongosMain] starting upgrade of config server from v5 to v6 <timestamp> I SHARDING [mongosMain] starting next upgrade step from v5 to v6 <timestamp> I SHARDING [mongosMain] about to log new metadata event: ... <timestamp> I SHARDING [mongosMain] checking that version of host ... is compatible with 2.6 ... <timestamp> I SHARDING [mongosMain] upgrade of config server to v6 successful ... <timestamp> I SHARDING [mongosMain] distributed lock 'configUpgrade/...' unlocked. <timestamp> I - [mongosMain] Config database is at version v6
The mongos will exit upon completion of the --upgrade process.
The upgrade will prevent any chunk moves or splits from occurring during the upgrade process. If the data files have many sharded collections or if failed processes hold stale locks, acquiring the locks for all collections can take seconds or minutes. Watch the log for progress updates.
Ensure mongos --upgrade process completes successfully.¶
The mongos will exit upon completion of the meta data upgrade process. If successful, the process will log the following messages:
<timestamp> I SHARDING [mongosMain] upgrade of config server to v6 successful ... <timestamp> I - [mongosMain] Config database is at version v6
If the mongos instance loses its connection to the config servers during the upgrade or if the upgrade is otherwise unsuccessful, you may always safely retry the upgrade.
Upgrade the remaining mongos instances to 3.0.¶
After you have successfully upgraded all mongos instances, you can proceed to upgrade the other components in your sharded cluster.
Change Sharded Cluster Storage Engine to WiredTiger¶
For a sharded cluster in MongoDB 3.0, you can choose to update the shards to use WiredTiger storage engine and have the config servers use MMAPv1. If you update the config servers to use WiredTiger, you must update all three config servers to use WiredTiger.
To change a sharded cluster to use WiredTiger, see Change Sharded Cluster to WiredTiger.
Upgrade Existing MONGODB-CR Users to Use SCRAM-SHA-1¶
After upgrading the binaries, see Upgrade to SCRAM-SHA-1 for details on SCRAM-SHA-1 upgrade scenarios.
General Upgrade Procedure¶
Except as described on this page, moving between 2.6 and 3.0 is a drop-in replacement: