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在 Node.js 中读写 Redis 的数据(失效时间和TTL)
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在开始本文之前请确保安装好 RedisNode.js 以及 Node.js 的 Redis 扩展 —— node_redis

首先创建一个新文件夹并新建文本文件 app.js 文件内容如下:

var redis = require("redis")
    , client = redis.createClient();
 
client.on("error", function (err) {
    console.log("Error " + err);
});
 
client.on("connect", runSample);
 
function runSample() {
    // Set a value
    client.set("string key", "Hello World", function (err, reply) {
        console.log(reply.toString());
    });
    // Get a value
    client.get("string key", function (err, reply) {
        console.log(reply.toString());
    });
}

当连接到 Redis 后会调用 runSample 函数并设置一个值,紧接着便读出该值,运行的结果如下:

OK
Hello World

我们也可以使用 EXPIRE 命令来设置对象的失效时间,代码如下:

var redis = require('redis')
    , client = redis.createClient();
 
client.on('error', function (err) {
    console.log('Error ' + err);
});
 
client.on('connect', runSample);
 
function runSample() {
    // Set a value with an expiration
    client.set('string key', 'Hello World', redis.print);
    // Expire in 3 seconds
    client.expire('string key', 3);
 
    // This timer is only to demo the TTL
    // Runs every second until the timeout
    // occurs on the value
    var myTimer = setInterval(function() {
        client.get('string key', function (err, reply) {
            if(reply) {
                console.log('I live: ' + reply.toString());
            } else {
                clearTimeout(myTimer);
                console.log('I expired');
                client.quit();
            }
        });
    }, 1000);
}

注意: 上述使用的定时器只是为了演示 EXPIRE 命令,你必须在 Node.js 项目中谨慎使用定时器。

运行上述程序的输出结果是:

Reply: OK
I live: Hello World
I live: Hello World
I live: Hello World
I expired

接下来我们检查一个值在失效之前存留了多长时间:

var redis = require('redis')
    , client = redis.createClient();
 
client.on('error', function (err) {
    console.log('Error ' + err);
});
 
client.on('connect', runSample);
 
function runSample() {
    // Set a value
    client.set('string key', 'Hello World', redis.print);
    // Expire in 3 seconds
    client.expire('string key', 3);
 
    // This timer is only to demo the TTL
    // Runs every second until the timeout
    // occurs on the value
    var myTimer = setInterval(function() {
        client.get('string key', function (err, reply) {
            if(reply) {
                console.log('I live: ' + reply.toString());
                client.ttl('string key', writeTTL);
            } else {
                clearTimeout(myTimer);
                console.log('I expired');
                client.quit();
            }
        });
    }, 1000);
}
 
function writeTTL(err, data) {
    console.log('I live for this long yet: ' + data);
}

运行结果:

Reply: OK
I live: Hello World
I live for this long yet: 2
I live: Hello World
I live for this long yet: 1
I live: Hello World
I live for this long yet: 0
I expired

英文原文OSCHINA原创翻译

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红薯
发帖于6年前 1回/13K+阅
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