Distributed Redis Caching In ASP.NET Core

In this article, we will see Distributed caching, Redis cache, and also Redis caching in ASP.NET Core.

Download source code from GitHub

Table of Content

What is distributed caching and its benefit
IDistributedCache interface
Framework provided to implement
Distributed Redis cache
Setting up Redis on Windows 10
Redis CLI commands
Steps to integrate Redis cache in ASP.NET core
Summary

What is distributed caching and its benefit

Distributed caching is when you want to handle caching outside of your application. This also can be shared by one or more applications/servers. Distributed cache is application-specific; i.e., multiple cache providers support distributed caches. To implement distributed cache, we can use Redis and NCache. We will see about Redis cache in detail.

A distributed cache can improve the performance and scalability of an ASP.NET Core app, especially when the app is hosted by a cloud service or a server farm.

Benefits

Data is consistent throughout multiple servers.
This is more suitable for microservice architecture
In case of loading balancing, this is recommended
Multiple Applications / Servers can use one instance of Redis Server to cache data. This reduces the cost of maintenance in the long run

IDistributedCache interface

IDistributedCache Interface provides you with the following methods to perform actions on the actual cache

GetAsync - Gets the Value from the Cache Server based on the passed key.
SetAsync - Accepts a key and Value and sets it to the Cache server
RefreshAsync - Resets the Sliding Expiration Timer (more about this later in the article) if any.
RemoveAsync - Deletes the cache data based on the key.

Framework provided to implement IDistributedCache

Register an implementation of IDistributedCache in Startup.ConfigureServices. Framework-provided implementations described in this topic include

Distributed Memory Cache
Distributed SQL Server cache
Distributed Redis cache
Distributed NCache cache

Distributed Redis cache

Redis is an open-source in-memory data store, which is often used as a distributed cache. You can configure an Azure Redis Cache for an Azure-hosted ASP.NET Core app, and use an Azure Redis Cache for local development.

Redis supports quite a lot of data structures like string, hashed, lists, queries, and much more and it’s a fast key-value-based database that is written in C. It’s a NoSQL database as well. For this purpose, it is being used in Stackoverflow, Github, and so on.

Setting Up Redis

We will see how we can setup Redis in local machine via two approaches (Currently I am using Window 10)

First Approach by Redis-server.exe

Run Redis-server.exe (Download from Github repo)

Minimize the Redis-server.exe and open Redis-cli.exe.
To test, just enter the command ping.

Second Approach via Chocolatey

Another way to install Redis on a Windows machine is chocolatey. To install chocolatey in a local machine, run the command given below from PowerShell (with administrative mode).

iex ((new-object net.webclient).DownloadString(‘https://chocolatey.org/install.ps1'))

This command downloads the chocolatey installer for Windows and using the command given below, we can install Redis on the local machine.

choco install redis-64

Once Redis Server is installed, use the command given below, where we can start Redis Server

redis-server

Running redis-server

I will use the first approach to run the server (ie., via redis-server.exe)
Go to the path and open up Powershell and run the following command
By default, Redis runs on the local 6379 port. To change the port number,

./redis-server --port {your_port}

Once Redis is running at your defined port, the Redis CLI will no longer work. This is because it tries to connect to 6379 by default. To override this, open up PowerShell again and enter the following command,

./redis-cli -p {your_port}

Redis CLI Commands

Below are some commands which run on power shell,

Setting a key with an expiration time (in seconds) and ttl name is for Time left to expire,

Steps to integrate Redis cache in ASP.NET core

Step 1

Make sure redis server is running,

./redis-server --port 6000

Step 2

Install the package that helps you communicate with the Redis server Microsoft.Extensions.Caching.StackExchangeRedis

Install-Package Microsoft.Extensions.Caching.StackExchangeRedis

Step 3

Configure in application to support Redis cache with a specific port.

In startup.cs/ConfigureServices method,

services.AddStackExchangeRedisCache(options =>
{
options.Configuration = "localhost:6000";
});

Step 4

Implementing caching code snippet in Get call of WeatherForeCastController,

[HttpGet]
public async Task < IActionResult > Get() {
var cacheKey = "weatherList";
string serializedCustomerList;
List < string > weatherList = new List < string > ();
var redisCustomerList = await _distributedCache.GetAsync(cacheKey);
if (redisCustomerList != null) {
serializedCustomerList = Encoding.UTF8.GetString(redisCustomerList);
weatherList = JsonConvert.DeserializeObject < List < string >> (serializedCustomerList);
} else {
weatherList = GetFromDb();
serializedCustomerList = JsonConvert.SerializeObject(weatherList);
redisCustomerList = Encoding.UTF8.GetBytes(serializedCustomerList);
var options = new DistributedCacheEntryOptions().SetAbsoluteExpiration(DateTime.Now.AddMinutes(10)).SetSlidingExpiration(TimeSpan.FromMinutes(2));
await _distributedCache.SetAsync(cacheKey, redisCustomerList, options);
}
return Ok(weatherList);
}

We check if the key has a value in Redis, then convert it to a weather list and send back the data and if the value does not exist in Redis, then access the database via efcore (in above code value is hardcoded), get the data and set it to Redis.

If the key has value then, the data will be stored in Redis as a byte array. We will be converting this array of a string which will convert the string to an object of type, List

DistributedCacheEntryOptions,

SetAbsoluteExpiration
Here you can set the expiration time of the cached object.
SetSlidingExpiration
This is similar to Absolute Expiration. It expires as a cached object if it not being requested for a defined amount of time period. Note that Sliding Expiration should always be set lower than the absolute expiration

Summary

In this detailed article, we have seen Distributed Caching in Redis. You can find the completed source code here. I hope you learned something new and detailed in this article.

Thanks and Happy Coding!