How to troubleshoot CentOS MongoDB

MongoDB troubleshooting guide for CentOS system

This article provides a systematic step to help you effectively troubleshoot MongoDB database problems on CentOS system. Follow the steps below to make the diagnosis step by step and carefully check the results of each step.

1. Check the system log

First, check whether there are error messages related to MongoDB in the system log:

• Use journalctl -xe command to view the system log and filter entries containing the keyword "mongodb".
• Check the MongoDB log file /var/log/mongodb/mongod.log directly, which usually contains detailed error information and operation records.

2. Check the configuration file

Confirm whether the settings of MongoDB configuration file /etc/mongod.conf are correct. Focus on the following configuration items:

• dbPath : Database data storage path
• logPath : log file storage path
• port : MongoDB listening port
• pidFilePath : Process ID file path

3. Verify service status

Use the following command to check the MongoDB service status:

• systemctl status mongod.service

4. Port occupation

Use the following command to check whether the 27017 port is occupied by MongoDB:

• netstat -anp | grep 27017 (If the port is occupied by other processes, please terminate the process)

5. Disk space and permissions

Make sure MongoDB's data directory has enough disk space and has correct read and write permissions.

6. MongoDB diagnostic tools

Use the diagnostic tools that come with MongoDB:

• mongostat : Real-time monitoring of MongoDB performance metrics.
• mongotop : Monitor database performance.
• db.serverStatus() : Get detailed status information of MongoDB instance, including locks, memory usage, and connection count. (Requires connection to MongoDB shell)

7. Analysis of crash dump (if any)

If the system crashes, analyze the dump file ( vmcore ) in the /var/crash directory to obtain kernel crash information. (Requires crash tool)

8. SELinux settings

If SELinux is enabled, check if its settings prevent MongoDB from running properly. You can temporarily set it to permissive mode for testing, or configure the corresponding SELinux rules for MongoDB.

9. Upgrade MongoDB version

Older versions of MongoDB may have known issues. Consider upgrading to the latest stable version.

10. Seek external help

If the above steps fail to resolve the problem, try:

• Search for MongoDB official documents and community forums to find solutions to similar problems.
• Contact MongoDB Technical Support Team for professional help.

Troubleshooting suggestions:

Stay patient, systematically troubleshoot problems, gradually narrow the scope, and finally find and solve the root cause of the problem. Record the results of each step, which will help you analyze the problem.

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