Redis Auto-Update Expiration Guide

Redis offers the feature of automatically refreshing expiration times, which can be achieved using the EXPIRE and TTL commands.

1. Set the value of a key using the SET command and set an expiration time using the EXPIRE command, for example:
2. Set the key with a specified value and set an expiration time for the key in seconds.
3. When it is necessary to refresh the expiration time, one can use the TTL command to retrieve the remaining expiration time of a key, and then use the EXPIRE command to extend it, for example:
4. Set a time-to-live (TTL) for a key
   Set an expiration time for a key in seconds
5. Note: The TTL command returns -1 if the key exists indefinitely, and -2 if the key does not exist or has expired.
6. You can use Redis transactions to ensure atomicity, meaning that no other operations will interfere between getting the remaining expiration time and setting a new expiration time.

Here is an example code using Redis for automatically refreshing expiration time (using Node.js and the ioredis library):

const Redis = require('ioredis');
const redis = new Redis();

const key = 'mykey';
const seconds = 60; // 设置过期时间为60秒

// 设置键的值和过期时间
redis.set(key, 'myvalue');
redis.expire(key, seconds);

// 自动刷新过期时间
setInterval(async () => {
  const ttl = await redis.ttl(key);
  if (ttl === -2) {
    console.log('Key does not exist or has expired');
    clearInterval(refreshInterval);
  } else if (ttl === -1) {
    console.log('Key exists and does not have an expiration');
  } else {
    console.log(`Refreshing expiration time: ${ttl} seconds left`);
    redis.expire(key, seconds);
  }
}, 5000); // 每5秒刷新一次过期时间

// 停止自动刷新过期时间
const refreshInterval = setInterval(() => {
  clearInterval(refreshInterval);
}, 60000); // 60秒后停止自动刷新

In the example above, the value and expiration time of a key are initially set using the SET and EXPIRE commands. The setInterval timer is then used to refresh the expiration time, checking every 5 seconds if the key is still present and has remaining time. If the key exists and still has time remaining, a new expiration time is set using the EXPIRE command. The clearInterval function is used to stop the auto-refresh after 60 seconds.