Table of contents
1.
Introduction
2.
Understanding MongoDB Logging
3.
Configuring MongoDB Log Levels
4.
Enabling Logging in MongoDB
5.
Analysing MongoDB Logs
6.
Monitoring MongoDB Logs in Real-time
7.
Frequently Asked Question
7.1.
How can we enable logging in MongoDB?
7.2.
Give all the main types of MongoDB logs.
7.3.
What log levels can we configure in MongoDB?
7.4.
How often should we analyse MongoDB logs?
7.5.
What tools can help analyse MongoDB logs?
8.
Conclusion
Last Updated: Mar 27, 2024
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How to Analyse and Monitor MongoDB Logs?

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Introduction

Have you ever worked on a database or any full-stack project in college? If yes, then you might be aware of MongoDB. It is a very popular NoSQL database which can store many data in a flexible manner and document-oriented format.

How to Analyse and Monitor MongoDB Logs?

So in the database system, keeping an eye on monitoring is very important, and analysing logs is also very important, so we will understand How to Analyse and Monitor MongoDB Logs.

Understanding MongoDB Logging

Mongodb generates different types of log files, each providing valuable insights into the database's activities and performance. The primary log files include:
 

  • MongoDB Log (mongod.log): It basically shows general info, warnings and errors in the logs.
     
  • MongoDB Query Log (query.log): It basically logs the queries which are from the recorded database with their execution time.
     
  • MongoDB Slow Query Log (slow_query.log): It basically shows the queries that are slow, which helps you to identify where you are lagging in the performance.

Configuring MongoDB Log Levels

To effectively analyse and monitor MongoDB logs, it's essential to configure the log levels according to your monitoring requirements. MongoDB provides various logging verbosity levels, including:

  • 0 (Default): Disables logging.
     
  • 1 (Error): Logs only error messages.
     
  • 2 (Warning): Logs warning messages.
     
  • 3 (Info): Logs informational messages.
     
  • 4 (Debug): Logs debugging information.

Enabling Logging in MongoDB

MongoDB allows users to enable logging either by modifying the configuration file (mongod.conf) or through runtime options. So below are the settings and steps for enabling the logs.
 

Step 1: First, we have to place the mongod.conf file into the  /etc/mongod.conf directory.
 

Step 2:  Set the below lines in the configuration file so that it will help to start the logging and also need to set the log path:

systemLog:

  destination: file
  logAppend: true
  path: /var/log/mongodb/mongod.log

 

Step 3: Here, we also need to set the log level from 1 to 4 by adding the below lines.

systemLog:

  verbosity: 2


Step 4: Save the changes and restart the MongoDB service.

Analysing MongoDB Logs

Now below are some important logs to analyse MongoDB:
 

Read and Interpret Logs: It helps to understand the database performance and also lets you know the health of the database on a regular basis using logs.
 

Use Log Analysis Tools: There are some tools like MongoDB Log Analyzer or mtools that help us to analyse and give insights into database operations.
 

Monitor Query Performance: It will let you help in analysing the performance of applications so that you can find where you are lagging behind in performance.
 

Detect Errors and Warnings: It is really very helpful during the development process. Here you will able to detect errors and warnings regularly.

Monitoring MongoDB Logs in Real-time

Analysing logs periodically is essential, but real-time monitoring can provide immediate insights and early detection of potential problems. Consider the following strategies for real-time MongoDB log monitoring:
 

Log Aggregation: For this, we can use many tools like Logstash, Elasticsearch and Kibana (ELK stack). These tools will help to analyse logs in real-time.
 

Alerting Mechanism: This enables swift action to prevent major issues. Here we need to set an alert so that we receive notifications whenever any important events or errors occur in the logs.
 

Performance Metrics: Combine log analysis with performance metrics monitoring to get a comprehensive view of your MongoDB's health and performance.

Frequently Asked Question

How can we enable logging in MongoDB?

So to enable the logging by changing mongod.conf with destination and log path settings.

Give all the main types of MongoDB logs.

There are three main types of logs: 1) MongoDB Log (mongod.log), 2) Query Log (query.log), and 2) Slow Query Log (slow_query.log).

What log levels can we configure in MongoDB?

MongoDB allows log levels ranging from 0 to 4 using the verbosity setting in the configuration.

How often should we analyse MongoDB logs?

Regularly analysing logs helps ensure the health and performance of your database, detecting potential issues promptly.

What tools can help analyse MongoDB logs?

In the above blog, we already covered. MongoDB Log Analyzer and mtools are useful tools for parsing and visualising MongoDB log data to gain insights.

Conclusion

In this article, we have covered How to Analyse and Monitor MongoDB Logs? We have also covered Configuring MongoDB Log Levels by Enabling Logging in MongoDB with proper steps.
Below are some very relevant articles that will help to gain more knowledge in MongoDB.
 

 

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