How to Repair MongoDB Database
This tutorial speaks about repairing a database using MongoDB in the Windows operating system depending on the problem we face.
Repair a Database in MongoDB
There are different scenarios where we need to repair a database using MongoDB. For instance, we repair a database if there is an improper or unclean shutdown or we want to check inconsistencies and errors.
We also repair the database if the system gets shut down accidentally. Before going into the repairing process, let’s understand the components of the MongoDB database.
MongoDB Database Components
The MongoDB database has three components, briefly explained below.
mongo- an interactive shell that checks the alert log; for instance, details and retries an operation.mongos- Process’ improper termination. Further, it was forced to disconnect from an instance.mongod- A daemon process that handles the background operations and data requests.
The following are some problems and the respective solutions.
Problem 1: System Gets Shutdown Accidentally
The following is the step-by-step solution for this issue. Remember to have a data folder in the root directory before following the steps.
-
Use the
cd/command to change the directory to theroot,C:\>in Windows OS. -
Copy the full path for the
mongod.exeservice. In our case, it isC:\Program Files\MongoDB\Server\5.0\bin\mongod.exe.Notice that we also added the
--repairparameter.C:\> "C:\Program Files\MongoDB\Server\5.0\bin\mongod.exe" --dbpath C:\data --repair -
Hit the Enter key and wait for this to finish. Once it is done, the database will be repaired.
Problem 2: Repair MongoDB for Improper Shutdown
The data may be inconsistent if the unclean shutdown happens and journaling is disabled while working in MongoDB. If there is a non-empty mongod.lock file, we will face the following error message.
Error Message:
Detected unclean shutdown – mongod.lock is not empty
The solution for this specific problem is given below.
-
Switch to the
rootdirectory using thecd/command on the Windows command prompt. -
We create data files’ backup copy in the
--dbpath. -
Use
--repairto initialize MongoDB. -
Execute the command given below and hit Enter.
C:\> mongod --dbpath /data/db --repair
Once it is finished, the MongoDB will be repaired.
Problem 3: Connect Failed Unclean Shutdown Detected
If any of us faces the following error, we must follow the 2-step process.
Error Message:
couldn't connect to server 127.0.0.1 shell/mongo.js:8 4 exceptions: connect failed Unclean shutdown detected
Step 1: Open the Windows Command Prompt and type cd/ to change the directory to the root.
Step 2: Execute the command as given below, press Enter and wait for this to end. Once it is done, the MongoDB is repaired now.
C:\> mongod --repair
