Keep MongoDb logfile size at bay

MongoDb is a great option for NoSql but sometimes it is installed in production forgetting some basic maintenance tasks, like managing log files. You should remember that MongoDb does not automatically rotate log files as for official documentation.

This lead to logfiles of Gigabyte size and sometimes they can even be a space problem in your installation. If a logfile is gone out of control, you cannot delete because it is in use by mongod process, so you need to ask for a manual rotate. Just connect to mongodb instance and from mongo.exe command line or any other tool you use issue this command.

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use admin
db.runCommand( { logRotate : 1 } )

This will force a file rotation, mongod process will create another file, and you are able to delete the old one.

As for the official documentation: MongoDB only rotates logs in response to the logRotate command, or when the mongod or mongos process receives a SIGUSR1 signal from the operating system

Another problem is, if you never rotate the files, when you need to examine mongodb log files, you need to find a program that is able to open text file of GB size. A better approach is to schedule the above command with mongo.exe tool.

.\mongo.exe localhost/admin -u admin -p mypassword --authenticationDatabase admin --eval "db.runCommand( { logRotate : 1 } )"

With this simple trick the size of your logfile will be always manageable.

Gian Maria.