Distributed cache using Redis and ASP.NET Core

What is Redis ?

Redis is a super fast non-relational database that uses keys to map to different data types. It is a key value data store (NoSQL) allowing to solve efficiently many different problem sets. Redis was created by Salvatore Sanfilippo in 2009, and Sanfilippo still remains the lead developer of the project today. It is a mature and hugely popular open source project, being used by many companies and in countless mission-critical production environments.

Here is an interview with the inventor of Redis, Salvatore Sanfilippo.

Why is Redis popular?

Not only is it extremely effective, but it is also relatively simple. Getting started with Redis is quite fast, and it usually takes only a few minutes to set up and get them working within an application. Thus, a small investment of time and effort can have an immediate, dramatic impact on performance of the application.

Just to name two cases when Redis is helpful:

Redis is used at Pinterest see use case or at Twitter, where Raffi Kirkorian, VP of Engineering at Twitter, explains how Redis helps to support over 30 billion timeline updates per day based on 5000 tweets per second or 400,000,000 tweets per day see here the presentation . Installing Redis Server on windows

Create a new ASP.NET Core project, and from Nuget select for installing Redis-64 . The server is installed in the default Nuget path. To start the server run next in command prompt:

C:\Users\[loggedin user]\.nuget\packages\Redis-64\[versioninstalled]\tools>redis-server.exe # in my case C:\Users\petru\.nuget\packages\Redis-64\3.0.503\tools>redis-server.exe

In the same folder, there is a document describing how to install Redis as a Windows Service (check the file Windows Service Documentation.docx ). For running the simple scenarios from this article, running just from command line should be enough.

Caching in ASP.NET Core using Redis

To use Redis in ASP.NET Core, we need to reference Microsoft.Extensions.Caching.Redis.Core package. Additionally, in our sample we would need also the Session package. Installing these could be done either using Nuget or extending the project.json file:

"Microsoft.Extensions.Caching.Redis.Core": "1.0.3", "Microsoft.AspNetCore.Session": "1.1.0"

To enable Redis in the application we need to add AddDistributedCache method in ConfigureServices method.

public void ConfigureServices(IServiceCollectionservices) { services.AddDistributedRedisCache(options => { options.InstanceName = "Sample"; options.Configuration = "localhost"; }); services.AddMvc(); }

To enable the session, we need to do changes in both ConfigureServices and Configure :

public void ConfigureServices(IServiceCollectionservices) { services.AddDistributedRedisCache(options => { options.InstanceName = "Sample"; options.Configuration = "localhost"; }); services.AddSession(); services.AddMvc(); } public void Configure(IApplicationBuilderapp, IHostingEnvironmentenv, ILoggerFactoryloggerFactory) { app.UseSession(); app.UseMvc(routes => { routes.MapRoute( name: "default", template: "{controller=Home}/{action=Index}/{id?}"); }); } How do we access Redis?

To cache a value in Redis we use:

var valueToStoreInRedis = Encoding.UTF8.GetBytes("This is a cached value from Redis"); HttpContext.Session.Set("TestProperty", valueToStoreInRedis);

To retrieve the value from cache we use:

var valueFromRedis = default(byte[]); if (HttpContext.Session.TryGetValue("TestProperty", out valueFromRedis)) valueToDisplay = Encoding.UTF8.GetString(valueFromRedis); Twitter client example

External interfaces to connect to social platforms are usually relatively slow to access. If we would do a web application showing messages from Twitter, it would take a couple of seconds to load the page (to make the search and retrieve). If the same user would connect again to our application, Redis could retrieve from memory the same messages, without accessing the server again. Caching the results, and updating them only when new messages appear, bring a huge improvement to the overall performance.

To keep the things simple, I have earlier written a small client in python, that connects to Twitter and save the details in a JSON file. You can read more details in the article Visual Studio Code Connect to Twitter with Python . It includes the full source code, and very fast you can access and save data in a JSON file.

In our sample here, we start from an already available JSON file.

[ { "Id": 0, "ProfileImage": "https://pbs.twimg.com/profile_images/1772973596/inogiclogo_normal.png", "ProfileDescription": "Microsoft Partner with Gold Competency in #Dynamics365 #MSDynCRM providing Solns/Services. Innovators of @Maplytics & Inolink #QuickBooks Int #MSDyn365 #MVPBuzz", "Username": "Inogic", "Text": "Execute the Global Action Using Web API in Dynamics CRM https://t.co/DAuzP6L7FE #MSDyn365 #webapi https://t.co/v0XgyotaFn", "ScreenName": "@inogic" }, .... ]

Retrieval of data from Twitter takes a couple of seconds. To simulate this, we add a delay of 20 seconds in our code. Here is the code from the controller.

public IActionResultIndex() { var watch = Stopwatch.StartNew(); string jSONText = RetrieveOrUpdateRedis(); watch.Stop(); TempData["DataLoadTime"] = watch.ElapsedMilliseconds; var itemsFromjSON = JsonConvert.DeserializeObject<IEnumerable<TwitterItem>>(jSONText); return View(itemsFromjSON); } private string RetrieveOrUpdateRedis() { var valueFromRedis = default(byte[]); string valueToReturn = string.Empty; if (HttpContext.Session.TryGetValue("TwitterDataset", out valueFromRedis)) { // Retrieve from Redis valueToReturn = Encoding.UTF8.GetString(valueFromRedis); TempData["DataLoadType"] = "From Redis"; } else { // read the file and update the URLs var jSONText = System.IO.File.ReadAllText("twitter.json"); valueToReturn = GetUpdatedFileContent(jSONText); // add an artificial delay of 20 seconds (simulating the search is done directly against a Twitter server) Thread.Sleep(20000); // store values in Redis var valueToStoreInRedis = Encoding.UTF8.GetBytes(valueToReturn); HttpContext.Session.Set("TwitterDataset", valueToStoreInRedis); TempData["DataLoadType"] = "From file"; } return valueToReturn; } // a minimum data processing, updating the URLs private string GetUpdatedFileContent(string jSONText) { var itemsFromjSON = JsonConvert.DeserializeObject<IEnumerable<TwitterItem>>(jSONText); foreach (var itemin itemsFromjSON) { Regex r = new Regex(@"(https?://[^\s]+)"); item.Text = r.Replace(item.Text, "<a href=\"$1\">$1</a>"); } return JsonConvert.SerializeObject(itemsFromjSON); } And here is the code to display data in the view. Twitter messages are displayed within