Node.js Service Log Reader with Prometheus Support

This Node.js program allows you to read a specific Linux service log and restart the service if certain conditions are met. It utilizes the child_process module to execute system commands, and it also integrates Prometheus for monitoring and alerting. Additionally, the program relies on an .env file for configuration.

Requirements

• Node.js (v12 or higher)
• npm (Node Package Manager)
• Linux environment with systemd
• Prometheus (optional)

Installation

1. Clone this repository to your local machine.

2. Navigate to the project directory and install dependencies:

   npm install
   

3. Prepare for you .env file

   PROM_PORT=9102
   MONITOR_SERVICE_NAME=your_service_name
   NUM_LOG_LINE=50
   LOG_THRESHOLDS=15
   PHRASE_TO_FIND="ERR"
   CHECK_INTERIVAL=60000
   

   Replace your_service_name with the name of the service you want to control and monitor. Set the PHRASE_TO_FIND to the phrase that you want to find in log file for the service. The PROM_PORT is the port where Prometheus will scrape metrics.

4. Start the program with

   npm run start
   

Features

• Read Service Log: The program will periodically read the specified service log file and look for a specific phrase related to a service error or problem.
• Restart Service: If the phrase is found in the log, the program will attempt to restart the service automatically.
• Prometheus Support: The program exposes Prometheus metrics on the specified port, allowing you to monitor the log occurrences and service restarts.

Prometheus Metrics

The program exposes the following Prometheus metrics:

service_${serviceName}_error_counter: The number of occurrences of the specific phrase found in the service log.

process_${serviceName}_restart_total: The total number of times the service has been restarted by the program.

Configuration

In the .env file, you can adjust the following variables:

• MONITOR_SERVICE_NAME: Replace with the name of your service (e.g., nginx, apache).
• PHRASE_TO_FIND: Set the phrase to finding in the log file of your service.
• PROM_PORT: Set the port where Prometheus will scrape metrics.
• NUM_LOG_LINE: Number of log lookup at once
• LOG_THRESHOLDS: How many times a the target phrase appeared to trigger restart
• CHECK_INTERVIAL: Time intervial for look up log

Monitoring

To monitor the metrics exposed by this program, you can configure Prometheus to scrape the metrics endpoint at http://your_server_ip:PROM_PORT/metrics.

License

This project is licensed under the MIT License.

Disclaimer

Use this program responsibly, and make sure you have proper access and permissions to control the service and access its logs. This program is provided as-is, and I am not responsible for any issues or damages caused by its usage. Please use it at your own risk.