PHP操作Redis队列实现数量控制（redis队列数量php）

Nowadays, most of web applications require some sort of resource allocation. Thus, it’s important to limit the number of requests and resources any single user can consume. If we don’t control the usage of the resources, it can easily cause devastating effects for the application and strn the underlying systems.

To provide this level of control, Queues are a great choice. A queue is a linear data structure (First In First Out or FIFO) where an item is removed from the front and added at the rear. Queues provide a mechanism for resource limitation and synchronization.

Today, we’ll see how we can use Redis to regulate the number of concurrent requests or resources we can process at a given time. Redis is a popular and open source in-memory data structure store that is mnly used as database, to cache/store data, or message broker.

To start, let’s define an example. Consider we’ve an application that processes a large number of jobs and runs on multiple servers. We need to ensure that the total number of jobs running concurrently doesn’t exceed 100.

The steps required to implement the limit are:

1. Create a named list (queue) in Redis to store the pending jobs

2. Each job is added to the list

3. When the job is processed, the server checks the length of the list

4. If the list contns more than 100 items, the server wts until the list contns less than or equal to 100 items

5. Once the length is below the limit, the server processes the job and reduces the list length

Now, let’s see how we can implement this using PHP.

First we’ll create a list in Redis to store our pending jobs.

$redis = new Redis();

$redis->connect(‘127.0.0.1’, 6379);

$redis->lPush(‘jobs’, ‘job1’);

Next, the server will check the total number of items in the list to make sure it’s not more than the limit. We can do this using the Redis LLEN command.

$listLength = $redis->lLen(‘jobs’);

while ($listLength > 100) {

sleep(2);

$listLength = $redis->lLen(‘jobs’);

}

Finally, once the list is below the limit, the server can process the job and remove it from the list. This is done using the Redis RPOPLPUSH command.

$job = $redis->rPopLPush(‘jobs’, ‘processed-jobs’);

// Process the job

// Remove the job from processed-jobs list

$redis->lRem(‘processed-jobs’, 0, $job);

In this way, we can use Redis and PHP to regulate the number of concurrent requests or resources we can process to avoid overloading the application or the underlying systems. Redis makes it easy to control the request count and ensure that requests don’t exceed a certn limit.