Scheduled tasks disappear after nodejs restarts

Node.js is a widely used server-side development language, and many applications rely on Node.js' scheduled tasks. However, when using Node.js, sometimes you encounter the problem of scheduled tasks disappearing after restarting. This problem affects the stability and normal operation of the application to a certain extent, so it needs to be resolved in time.

In this article, we will introduce step by step the problem of scheduled tasks disappearing in Node.js and its solution.

1. Problem description

In Node.js applications, we usually use setTimeout or setInterval to perform scheduled tasks. These functions allow us to set a time interval and then execute a piece of code at this interval, looping until we don't need it to stop.

However, when Node.js was restarted, we found that these scheduled tasks disappeared and they needed to be restarted manually. This will cause us to constantly monitor the running status of the application, which consumes a lot of time and energy.

2. Cause of the problem

In Node.js, when we start a scheduled task, it will be added to an event queue. When the event loop reaches this task, it will Execute the corresponding code according to the time interval we set. However, when we restart Node.js, the entire event queue will be cleared, so all scheduled tasks will disappear.

3. Solution

In order to solve this problem, we can use pm2, the Node.js process management tool. pm2 can help us manage the Node.js process and maintain application stability and high availability.

The specific solution is as follows:

Step 1: Install pm2

Use npm to install pm2:

npm install -g pm2

Step 2: Start the Node.js application

Use pm2 to start the Node.js application:

pm2 start app.js

The app.js here is our application entry file.

Step 3: Set up scheduled tasks

Use the pm2 command to set up scheduled tasks:

pm2 cron [interval] [command] [-d args]

Among them, interval is the time interval of the scheduled task, in seconds or cron expression; command is the command we want to execute; args are the parameters we want to pass to the command.

For example, if we want to execute the command node process.js every 30 seconds, we can use the following command:

pm2 cron '*/30 * * * * *' 'node process.js'

Note: When using pm2 to set up scheduled tasks, we need to Set the cron executable path in the configuration file so that pm2 knows which version of Node.js to run.

Step 4: Save the pm2 configuration file

Save the pm2 configuration file using the following command:

pm2 save

This will make our configuration file permanently saved and available the next time the app starts Load automatically.

Through the above steps, we can solve the problem of scheduled tasks disappearing after Node.js restarts.

Summary

The scheduled tasks of Node.js are an important part of the application, so we need to ensure their stability and reliability. By using the pm2 process management tool, we can easily set up and manage scheduled tasks to maintain the normal operation and high availability of applications.

The above is the detailed content of Scheduled tasks disappear after nodejs restarts. For more information, please follow other related articles on the PHP Chinese website!