🗃️Cache

• Introduction

• Configuration

  • Driver Prerequisites

• Cache Usage

  • Obtaining a Cache Instance

  • Retrieving Items From the Cache

  • Storing Items in the Cache

  • Removing Items From the Cache

  • The Cache Helper

• Atomic Locks

  • Managing Locks

  • Managing Locks Across Processes

• Adding Custom Cache Drivers

  • Writing the Driver

  • Registering the Driver

• Events

Introduction

Some of the data retrieval or processing tasks performed by your application could be CPU intensive or take several seconds to complete. When this is the case, it is common to cache the retrieved data for a time so it can be retrieved quickly on subsequent requests for the same data. The cached data is usually stored in a very fast data store such as Memcached or Redis.

Thankfully, Maginium provides an expressive, unified API for various cache backends, allowing you to take advantage of their blazing fast data retrieval and speed up your web application.

Configuration

Your application's cache configuration file is located at app/etc/env.php. In this file, you may specify which cache store you would like to be used by default throughout your application. Maginium supports popular caching backends like Memcached, Redis, DynamoDB, and relational databases out of the box. In addition, a file-based cache driver is available, while array and "null" cache drivers provide convenient cache backends for your automated tests.

The cache configuration file also contains a variety of other options that you may review. By default, Maginium is configured to use the redis cache driver, which stores the serialized, cached objects in your redis's instance.

Driver Prerequisites

Memcached

Using the Memcached driver requires the Memcached PECL package to be installed. You may list all of your Memcached servers in the app/etc/env.php configuration file. This file already contains a memcached.servers entry to get you started:

MEMCACHED_HOST='/var/run/memcached/memcached.sock' || '127.0.0.1'
MEMCACHED_PORT= 0 || 11211
#MEMCACHED_WEIGHT=100

Redis

Before using a Redis cache with Maginium, you will need to either install the PhpRedis PHP extension via PECL or install the predis/predis package (~2.0) via Composer. Maginium Sail already includes this extension. In addition, official Maginium deployment platforms such as Maginium Forge and Maginium Vapor have the PhpRedis extension installed by default.

For more information on configuring Redis, consult its Maginium documentation page.

DynamoDB

Before using the DynamoDB cache driver, you must create a DynamoDB table to store all of the cached data. Typically, this table should be named cache. However, you should name the table based on the value of the stores.dynamodb.table configuration value within the cache configuration file. The table name may also be set via the DYNAMODB_CACHE_TABLE environment variable.

This table should also have a string partition key with a name that corresponds to the value of the stores.dynamodb.attributes.key configuration item within your application's cache configuration file. By default, the partition key should be named key.

Typically, DynamoDB will not proactively remove expired items from a table. Therefore, you should enable Time to Live (TTL) on the table. When configuring the table's TTL settings, you should set the TTL attribute name to expires_at.

Next, install the AWS SDK so that your Maginium application can communicate with DynamoDB:

composer require aws/aws-sdk-php

In addition, you should ensure that values are provided for the DynamoDB cache store configuration options. Typically these options, such as AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY, should be defined in your application's .env configuration file:

# AWS Creds.
AWS_ACCESS_KEY_ID=
AWS_SECRET_ACCESS_KEY=
AWS_DEFAULT_REGION=us-east-1

# DynamoDB Configs.
DYNAMODB_CACHE_TABLE=cache
DYNAMODB_ENDPOINT=

MongoDB

If you are using MongoDB, a mongodb cache driver is provided by the official mongodb/maginium-mongodb package and can be configured using a mongodb database connection. MongoDB supports TTL indexes, which can be used to automatically clear expired cache items.

For more information on configuring MongoDB, please refer to the MongoDB Cache and Locks documentation.

Cache Usage

Obtaining a Cache Instance

To obtain a cache store instance, you may use the Cache facade, which is what we will use throughout this documentation. The Cache facade provides convenient, terse access to the underlying implementations of the Maginium cache contracts:

<?php

namespace App\Http\Controllers;

use Maginium\Framework\Support\Collections\Facades\Cache;

class UserController extends Controller
{
    /**
     * Show a list of all users of the application.
     */
    public function index(): array
    {
        $value = Cache::get('key');

        return [
            // ...
        ];
    }
}

Accessing Multiple Cache Stores

Using the Cache facade, you may access various cache stores via the store method. The key passed to the store method should correspond to one of the stores listed in the stores configuration array in your cache configuration file:

$value = Cache::store('file')->get('foo');

Cache::store('redis')->put('bar', 'baz', 600); // 10 Minutes

Retrieving Items From the Cache

The Cache facade's get method is used to retrieve items from the cache. If the item does not exist in the cache, null will be returned. If you wish, you may pass a second argument to the get method specifying the default value you wish to be returned if the item doesn't exist:

$value = Cache::get('key');

$value = Cache::get('key', 'default');

You may even pass a closure as the default value. The result of the closure will be returned if the specified item does not exist in the cache. Passing a closure allows you to defer the retrieval of default values from a database or other external service:

$value = Cache::get('key', function () {
    return DB::table(/* ... */)->get();
});

Determining Item Existence

The has method may be used to determine if an item exists in the cache. This method will also return false if the item exists but its value is null:

if (Cache::has('key')) {
    // ...
}

Incrementing / Decrementing Values

The increment and decrement methods may be used to adjust the value of integer items in the cache. Both of these methods accept an optional second argument indicating the amount by which to increment or decrement the item's value:

// Initialize the value if it does not exist...
Cache::add('key', 0, now()->addHours(4));

// Increment or decrement the value...
Cache::increment('key');
Cache::increment('key', $amount);
Cache::decrement('key');
Cache::decrement('key', $amount);

Retrieve and Store

Sometimes you may wish to retrieve an item from the cache, but also store a default value if the requested item doesn't exist. For example, you may wish to retrieve all users from the cache or, if they don't exist, retrieve them from the database and add them to the cache. You may do this using the Cache::remember method:

$value = Cache::remember('users', $seconds, function () {
    return DB::table('users')->get();
});

If the item does not exist in the cache, the closure passed to the remember method will be executed and its result will be placed in the cache.

You may use the rememberForever method to retrieve an item from the cache or store it forever if it does not exist:

$value = Cache::rememberForever('users', function () {
    return DB::table('users')->get();
});

Stale While Revalidate

When using the Cache::remember method, some users may experience slow response times if the cached value has expired. For certain types of data, it can be useful to allow partially stale data to be served while the cached value is recalculated in the background, preventing some users from experiencing slow response times while cached values are calculated. This is often referred to as the "stale-while-revalidate" pattern, and the Cache::flexible method provides an implementation of this pattern.

The flexible method accepts an array that specifies how long the cached value is considered “fresh” and when it becomes “stale.” The first value in the array represents the number of seconds the cache is considered fresh, while the second value defines how long it can be served as stale data before recalculation is necessary.

If a request is made within the fresh period (before the first value), the cache is returned immediately without recalculation. If a request is made during the stale period (between the two values), the stale value is served to the user, and a deferred function is registered to refresh the cached value after the response is sent to the user. If a request is made after the second value, the cache is considered expired, and the value is recalculated immediately, which may result in a slower response for the user:

$value = Cache::flexible('users', [5, 10], function () {
    return DB::table('users')->get();
});

Retrieve and Delete

If you need to retrieve an item from the cache and then delete the item, you may use the pull method. Like the get method, null will be returned if the item does not exist in the cache:

$value = Cache::pull('key');

$value = Cache::pull('key', 'default');

Storing Items in the Cache

You may use the put method on the Cache facade to store items in the cache:

Cache::put('key', 'value', $seconds = 10);

If the storage time is not passed to the put method, the item will be stored indefinitely:

Cache::put('key', 'value');

Instead of passing the number of seconds as an integer, you may also pass a DateTime instance representing the desired expiration time of the cached item:

Cache::put('key', 'value', now()->addMinutes(10));

Store if Not Present

The add method will only add the item to the cache if it does not already exist in the cache store. The method will return true if the item is actually added to the cache. Otherwise, the method will return false. The add method is an atomic operation:

Cache::add('key', 'value', $seconds);

Storing Items Forever

The forever method may be used to store an item in the cache permanently. Since these items will not expire, they must be manually removed from the cache using the forget method:

Cache::forever('key', 'value');

If you are using the Memcached driver, items that are stored "forever" may be removed when the cache reaches its size limit.

Removing Items From the Cache

You may remove items from the cache using the forget method:

Cache::forget('key');

You may also remove items by providing a zero or negative number of expiration seconds:

Cache::put('key', 'value', 0);

Cache::put('key', 'value', -5);

You may clear the entire cache using the flush method:

Cache::flush();

Flushing the cache does not respect your configured cache "prefix" and will remove all entries from the cache. Consider this carefully when clearing a cache which is shared by other applications.

The Cache Helper

In addition to using the Cache facade, you may also use the global cache function to retrieve and store data via the cache. When the cache function is called with a single, string argument, it will return the value of the given key:

$value = cache('key');

If you provide an array of key / value pairs and an expiration time to the function, it will store values in the cache for the specified duration:

Cache(['key' => 'value'], $seconds);

cache(['key' => 'value'], now()->addMinutes(10));

When the cache function is called without any arguments, it returns an instance of the Illuminate\Contracts\Cache\Factory implementation, allowing you to call other caching methods:

Cache()->remember('users', $seconds, function () {
    return DB::table('users')->get();
});

When testing calls to the global \`cache\` function, you may use the \`Cache::shouldReceive\` method just as if you were \[testing the facade]\(../docs/%7B%7Bversion%7D%7D/mocking/#mocking-facades).

Atomic Locks

To utilize this feature, your application must be using the `memcached`, `redis`, `dynamodb`, `file`, or `array` cache driver as your application's default cache driver. In addition, all servers must be communicating with the same central cache server.

Managing Locks

Atomic locks allow for the manipulation of distributed locks without worrying about race conditions. For example, Maginium Forge uses atomic locks to ensure that only one remote task is being executed on a server at a time. You may create and manage locks using the Cache::lock method:

use Maginium\Framework\Support\Collections\Facades\Cache;

$lock = Cache::lock('foo', 10);

if ($lock->get()) {
    // Lock acquired for 10 seconds...

    $lock->release();
}

The get method also accepts a closure. After the closure is executed, Maginium will automatically release the lock:

Cache::lock('foo', 10)->get(function () {
    // Lock acquired for 10 seconds and automatically released...
});

If the lock is not available at the moment you request it, you may instruct Maginium to wait for a specified number of seconds. If the lock cannot be acquired within the specified time limit, an Illuminate\Contracts\Cache\LockTimeoutException will be thrown:

use Illuminate\Contracts\Cache\LockTimeoutException;

$lock = Cache::lock('foo', 10);

try {
    $lock->block(5);

    // Lock acquired after waiting a maximum of 5 seconds...
} catch (LockTimeoutException $e) {
    // Unable to acquire lock...
} finally {
    $lock->release();
}

The example above may be simplified by passing a closure to the block method. When a closure is passed to this method, Maginium will attempt to acquire the lock for the specified number of seconds and will automatically release the lock once the closure has been executed:

Cache::lock('foo', 10)->block(5, function () {
    // Lock acquired after waiting a maximum of 5 seconds...
});

Managing Locks Across Processes

Sometimes, you may wish to acquire a lock in one process and release it in another process. For example, you may acquire a lock during a web request and wish to release the lock at the end of a queued job that is triggered by that request. In this scenario, you should pass the lock's scoped "owner token" to the queued job so that the job can re-instantiate the lock using the given token.

In the example below, we will dispatch a queued job if a lock is successfully acquired. In addition, we will pass the lock's owner token to the queued job via the lock's owner method:

$podcast = Podcast::find($id);

$lock = Cache::lock('processing', 120);

if ($lock->get()) {
    ProcessPodcast::dispatch($podcast, $lock->owner());
}

Within our application's ProcessPodcast job, we can restore and release the lock using the owner token:

Cache::restoreLock('processing', $this->owner)->release();

If you would like to release a lock without respecting its current owner, you may use the forceRelease method:

Cache::lock('processing')->forceRelease();

Events

To execute code on every cache operation, you may listen for various events dispatched by the cache:

Event Name
Maginium\Framework\Cache\Collections\Events\CacheHit
Maginium\Framework\Cache\Collections\Events\CacheMissed
Maginium\Framework\Cache\Collections\Events\KeyForgotten
Maginium\Framework\Cache\Collections\Events\KeyWritten