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Backup

Logs Display MongodVersionException

The MongodVersionException can occur if the Backup Daemon’s host cannot access the internet to download the version or versions of MongoDB required for the backed-up databases. Each database requires a version of MongoDB that matches the database’s version. Specifically, for each instance you must run the latest stable release of that release series.

If the Daemon runs without access to the internet, you must manually download the required MongoDB versions, as described here:

  1. Go to the MongoDB downloads page and download the appropriate versions for your environment.

  2. Copy the download to the Daemon’s host.

  3. Decompress the download into the directory specified in the mongodb.release.directory setting in the Daemon’s conf-daemon.properties file. To learn the file’s location, see Ops Manager Configuration.

    Within the directory specified in the mongodb.release.directory setting, the folder structure for MongoDB should look like the following:

    <path-to-mongodb-release-directory>/
    |-- mongodb-<platform>
    |  |-- THIRD-PARTY-NOTICES
    |  |-- README
    |  |-- bin
    |  |  |-- bsondump
    |  |  |-- mongo
    |  |  |-- mongod
    |  |  |-- mongodump
    |  |  |-- mongoexport
    |  |  |-- mongofiles
    |  |  |-- mongoimport
    |  |  |-- mongooplog
    |  |  |-- mongoperf
    |  |  |-- mongorestore
    |  |  |-- mongos
    |  |  |-- mongostat
    |  |  |-- mongotop
    

Insufficient Oplog Size Error

When using the Ops Manager interface to back up a MongoDB cluster, Ops Manager checks to see if the cluster’s oplogs are, based on their recent usage, large enough to hold a minimum of 3 hours worth of data based on the last 24 hours of usage patterns. If the oplogs are not large enough, it may be possible that the oplogs may have turned over multiple times, creating a gap between where a backup ends and an oplog starts.

If the oplog size check fails, the user cannot enable backups and is shown the warning:

Warning

Insufficient oplog size: The oplog window must be at least 3 hours over the last 24 hours for all members of replica set <name>. Please increase the oplog.

If possible, wait to start a backup until the oplog has had sufficient time to meet the size requirement.

If this is not possible, the minimum oplog size value can be changed. See mms.backup.minimumOplogWindowHours for how to set this value.

Warning

Do not change the minimum oplog size unless you are certain smaller backups still provide useful backups.

Important

MongoDB recommends only changing this value temporarily to permit a test backup job to execute. The minimum oplog size value should be reset to the default as soon as possible. If an oplog is set to too small of a value, it can result in a gap between a backup job and an oplog which makes the backup unusuable for restores. Stale backup jobs must be resynchronized before it can be used for restores.

Understanding the risks given, you can start backups using this changed minimum value. Once you pass the 24 hour mark, you should reset this minimum value to preserve the sanity check for the global Ops Manager installation going forward.

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