Migrating your database to work with the MongoDB WiredTiger storage engine

MainView Middleware Administrator (MVMA) uses the MongoDB WiredTiger storage engine by default.

Prerequisites

• If you are upgrading from a previous version of TrueSight Middleware Administrator (TSMA) to MVMA 9.0.00, you must migrate the TSMA database from the previously used Memory Map storage engine (MMAPv1) to WiredTiger.
• Ensure this installation’s instance of MongoDB is using the installation’s MongoDB configuration file in its original format (i.e. not in the YAML format) and is using this installation’s original data directory for storing data. If this instance of MVMA is configured to use a separate or non-default instance of MongoDB the migration tool cannot be used and it is recommended to consult the MongoDB product documentation for migrating that instance of MongoDB to WiredTiger manually.
• When applying to a current MVMA 9.0.00 installation, the migration tool will abort after detecting the configured storage engine is WiredTiger.
• The migration should be performed immediately after upgrading the installation.

Installing the migration tool

• The migration tool is installed with a MVMA 9.0.00 installation.
• The (platform-specific) command script to be run is installed in the 'bin' sub-directory.
• The related Java component is installed in the 'migrate' sub-directory.

To migrate MVMAwith MongoDB when not running in a Replica Set

To migrate MVMA databases after a MVMA upgrade installation for MVMA running in the default configuration, i.e. with MongoDB as a standalone instance, perform the following steps:

1. Verify MVMA including MongoDB is stopped.
2. After an installation upgrade from TSMA 8.2 or earlier to MVMA 9.0, open a command prompt and navigate to the MVMA installation directory.
3. Ensure that MVMA and MongoDB are stopped prior to running the data migration command.
4. On Windows run the following command: .\bin\migrateMongoDB.bat
   On Linux run the following command: ./bin/migrateMongoDB
5. Ensure from the command output that the data migration has completed successfully.
6. As part of the migration the command creates the following backup resources, assigning the migration timestamp at the end of the resource created:
   

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     _installdir>/data.bkp.<timestamp> - a backup of the original data directory.

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     _installdir>/data.export.<timestamp> - the MongoDB export as created by the MongoDB mongodump command.

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     _installdir>/etc/data.conf.bkp.<timestamp> - a backup of the original MongoDB configuration file.

7. After the migration, perform the following steps:
   • Review the migrated MongoDB configuration file etc/data.conf to make sure any of your custom settings were preserved and the storageEngine setting was migrated to wiredTiger.
   • Save or remove the backup resources created during migration, as required.
8. Start MVMA (which, by default, will also start MongoDB).

See also the MongoDB product documentation for instructions to migrate a standalone instance of MongoDB to WiredTiger: https://docs.mongodb.com/v3.2/tutorial/change-standalone-wiredtiger/ 

To migrate MVMA running MongoDB in a Replica Set

Migrating with MongoDB up and running is the suggested way to migrate MVMA running with a MongoDB replica set. Migrating MVMA MongoDB benefits from MongoDB's capability to perform an initial sync with a secondary instance and to elect another primary instance if the current primary went down.

See also the MongoDB product documentation for instructions to migrate a replica set of MongoDB to WiredTiger: https://docs.mongodb.com/v3.2/tutorial/change-replica-set-wiredtiger/ 

1. Verify the following:
   • Make sure all instances of MongoDB in the assigned replica set are up and running and have joined the replica set.
   • Make sure all instances of MVMA services on the replica set nodes are stopped.
   • Identify the current secondaries and the current primary in the replica set.
     This is done from the install dir on one machine and running mongodb\mongodb-win32-x86_64-3.2.17\bin\mongo.exe to start the mongo shell.
     Then run the following command: rs.status ()
2. For every secondary replica set node:
   
   • Stop MongoDB.
   • On Windows run the following command: .\bin\migrateMongoDB.bat
     On Linux run the following command: ./bin/migrateMongoDB
   • Re-start MongoDB.
   • Wait until this instance of MongoDB has initialized and has re-joined the replica set.
3. Stop MongoDB for the primary instance.
4. On Windows run the following command: .\bin\migrateMongoDB.bat
   On Linux run the following command: ./bin/migrateMongoDB
5. Re-start MongoDB.
6. Wait until this instance of MongoDB has initialized and has re-joined the replica set.
7. Re-start MVMA services on all nodes of the replica set.