What is mongodb oplog

Use the command bsondump to inspect the. If the dump is too big, you can use grep or any other tool to find the commands:. If running mongorestore with --oplogReplay , the restore role is insufficient to replay the oplog. To replay the oplog, create a user-defined role that has anyAction on anyResource and grant only to users who must run mongorestore with --oplogReplay.

Copy the application folder to have a backup of your upload files. Files that you have been uploaded to your database may not be included in the full backup described above. Check the users in the admin database to make sure it does not exist any unknown user in case your server has been attacked. Basically the OpLog is a collection a collection can be thought of a table in a database of write operations updates, deletes, inserts which are stored in order of operation, this allows other members of the replica set cluster to apply these changes to the local copy of their database.

This is a very good question. The OpLog is a capped collection which means it only stores a certain number of records after that number is reached the oldest record is dropped from the OpLog. The oplog can be queried like any other collection. From the shell here is an example of how to query the oplog:.

Can I use oplog to trigger another program? I mean as soon as a data operation is performed on mongodb, can I use Oplog to execute some program? Yes you can do this. However, after you have started a replica set member for the first time, you can only change the size of the oplog using the Change the Size of the Oplog procedure.

Conversely, if your application predominantly performs reads with a minimal amount of write operations, a smaller oplog may be sufficient. The oplog must translate multi-updates into individual operations in order to maintain idempotency.

This can use a great deal of oplog space without a corresponding increase in data size or disk use. If you delete roughly the same amount of data as you insert, the database will not grow significantly in disk use, but the size of the operation log can be quite large. If a significant portion of the workload is updates that do not increase the size of the documents, the database records a large number of operations but does not change the quantity of data on disk.

To view oplog status, including the size and the time range of operations, issue the rs. For more information on oplog status, see Check the Size of the Oplog.