Skip to main content

.NET Core Distributed SQL Server Cache


Introduction:

A caching that can be shared or consumed by the multiple apps servers can be called a Distributed Cache. Distributed Cache is an external service, which increases the performance and scalability of applications. The advantages of Distributed Cache are like:
  • No effect on the cache server on an application crash.
  • No need to use local memory.
  • Consistency in serving cached data around multiple applications.
In General, Distributed Cache can be achieved by using Redi's Cache, SQL Cache, Third Party Cache Libraries. Here we will learn about .NET Core Distributed SQL Server Cache.

Create A .NET Core WebAPI Project:

Create a sample .NET Core Web API application to test the Distributed Cache. You can use either Visual Studio 2019 or Visual Studio Code editor, here I'm using Visual Studio Code. Click here to know basics steps to use Visual Studio Code for .NET Core applications

SQL Table For Cache:

To store the cache data we need a table. So .NET Core has defined a structure of the table like how the table should be and what the table should store data, in simple words a templated predefined cache table.

To create a SQL cache table .NET Core provided CLI command as follows.
dotnet sql-cache create "your_database_connection_string" dbo your_cache_table_name
If having any issue to create the SQL cache table using the above CLI command, we can create the cache table manually, but the column names and column type should match as .NET core prescribed by default. So run the following SQL script query to create a cache table.
CREATE TABLE [dbo].[MyCache]
(
    [Id] NVARCHAR(900) NOT NULL PRIMARY KEY, 
    [Value] VARBINARY(MAX) NOT NULL, 
    [ExpiresAtTime] DATETIMEOFFSET NOT NULL, 
    [SlidingExpirationInSeconds] BIGINT NULL, 
    [AbsoluteExpiration] DATETIMEOFFSET NULL
)
'Id' Column - is a primary column of type String. In this column, we need to store a 'key' value which helps query the table.
'Value' Column - its type is Binary. In these columns, we need to store data to be cached and stores the data in binary format.
'SlidingExpirationInSeconds' Column - its type is BigInt. In this column, we need to store time in seconds. If the record is not consumed by any application or client which means the record is idle for specified seconds in the 'SlidingExpirationInSeconds' then the record will be in expired state. Which means no client can consume this record.
'ExpiresAtTime' Column - its type is DateTime. In this column, we need to store the idle expiration DateTime. This means its value will be created by adding the total number of seconds in the 'SlidingExpirationInSeconds' column to the current DateTime.
'AbsoluteExpiration' Column - its type is DateTime. In this column, we need to store the absolute expiration of DateTime means a max lifetime of the record. 'ExpiresAtTime' column must be within the limit of the 'AbsoluteExpiration' column value.

Install SQL Server Cache NuGet:

Microsft provided an extended NuGet package for SQL Server Cache. Use the below command to install the package.
Package Manager:
Install-Package Microsoft.Extensions.Caching.SqlServer -Version 3.1.3
.NET CLI:
dotnet add package Microsoft.Extensions.Caching.SqlServer --version 3.1.3

Configure AddDistributedSqlServerCache Service:

Configure the cache database connection string to the app.setting.json file.
app.setting.json:
"ConnectionStrings":{
   "MyWorldDbConnection":"Your_databse_connectionString"
}
Configure AddDistributedSqlServerCache Service provider in Startup.cs file.
Startup.cs:
services.AddDistributedSqlServerCache(options => {
 options.ConnectionString = Configuration.GetConnectionString("MyWorldDbConnection");
 options.SchemaName = "dbo";
 options.TableName = "MyCache";
});
  • ConnectionString mapped to the value in the app.setting.json file. 
  • "dbo" is a SQL database schema. 
  • TableName mapped to the cache table which we created at the initial step.

IDistributedCache Interface:

IDistributedCache Interface is implemented from 'Microsoft.Extensions.Caching.Distributed' library. IDistributeCache is not specific to SQL Server Cache, but it was implemented like generic which supports all kinds of Distributed Cache like Redis, SQL Server Cache, etc. IDistributeCache supports the default dependency inject of .NET Core, so it can be easily injected in the application where ever needed. IDistributedCache Interface holds a set of methods that helps to work with cache, some of the methods like as below.
  • Get, GetAsync - fetches the cached data by the key passed to the method.
  • Set, SetAsync - saves the data to the cache table with a specific key.
  • Remove, RemoveAsync - removes the cached data with specific to key passed.
Create an API controller and inject the IDistributedCache interface into its constructor as below.
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Caching.Distributed;
namespace SqlDistributedCache.API.Controllers
{
    [ApiController]
    [Route("[controller]")]
    public class TestController: ControllerBase
    {
        private readonly IDistributedCache _distributedCache;
        public TestController(IDistributedCache distributedCache)
        {
            _distributedCache = distributedCache;
        }
    }
}

Save Data To SQL Cache Table:

IDistributedCache interface provided a method like SetAsync, SetStringAsync to store cache data.

SetAsync - this method expects data to be stored as Byte[]. So on using SetAsync overloaded methods we need explicitly convert the data to Byte[].

SetStringAsync - this is an extended method implemented by 'Microsoft.Extensions.Caching.Distributed'. So on using this method it simply expects the stored data to be String format. Internally it will convert that String data to Byte[] while saving to cache table.
Note:
IDistributedCache interface also provides non async methods like Set, SetString , but async methods recomended.
Here in the sample, we explore using SetStringAsync. let's look more about the SetStringAsync overloaded methods as below.

  • SetStringAsync(string key,string value, DistributedCacheEntryOptions options, CancellationToken token = default) in this overloaded method we pass 'key', 'value'(data to be catches), 'DistributeCacheEntryOptions' provides an explicit way of defining the expiration Date Time into our cache table
  • SetStringAsync(string key, string value, CancellationToken token = default) in this overload method we simply pass 'key' and data as string format to 'value' variable. Here we don't have an option to specify DateTime explicitly. So on using this method expiration Date Time will be assigned with default values that are implicitly or explicitly configured in 'AddDistributedSqlServerCache' service.
Let test cache saving using SetStringAsync method without 'DistributedCacheEntryOptions' parameter as follow
TestController.cs:
[Route("add-cache-no-time-options")]
[HttpGet]
public async Task<IActionResult> AddCacheNoTimeOptions()
{
 string key = "test1";
 string value = "naveen";
 await _distributedCache.SetStringAsync(key, value);
 return Ok("success");
}
Now test this API route and check record added in the cache table.

  • In the 'Value' column the data to be cached is stored in Binary format.
  • In the 'Id' column stores key value.
  • Since we didn't specify any expiration options explicitly, then the default options set by the 'AddDistributedSqlServerCache' service will be stored in 'ExpiresAtTime', 'SlidingExpirationInSeconds' columns.
  • The default value for 'SlidingExpirationInSeconds' 20 minutes which will be saved as seconds(1200 seconds).
  • The default value for 'ExpiresAtTime' is the addition of current date time value with 'SlidingExpirationInSeconds' column.
Let's test the cache saving using the SetStringAsync method with the 'DistributedCacheEntryOptions' parameter which means specifying expiration values explicitly as follows.
[Route("add-cache")]
[HttpGet]
public async Task<IActionResult> AddCache()
{
 string key = "test2";
 string value = "Naveen Bommindi";
 DistributedCacheEntryOptions options = new DistributedCacheEntryOptions
 {
  SlidingExpiration = TimeSpan.FromMinutes(1),
  AbsoluteExpirationRelativeToNow = TimeSpan.FromHours(1)
 };
 await _distributedCache.SetStringAsync(key, value, options);
 return Ok("success");
}
  • 'DistributedCacheEntryOptions' type helps to explicitly specify the expiration time values. 
  • Here property like 'SlidingExpiration' to 1 minute, this explains after being idle for 1 minute this record state will be expired. This 'SlidingExpiration' property value will be saved to the 'SlidingExpirationInSeconds' column in the cache table. 
  • Based on 'SlidingExpirationInSeconds' value, the column  'ExpireAtTime' value will be assigned(current date-time plus 'SlidingExpirationInSeconds' column value). 
  • Here property like 'AbsoluteExpirationRelativeToNow' is like the main expiration date-time, it will save the value in the 'AbsoluteExpiration' column. So the value in 'ExpireAtTime' value should be within the limits of the 'AbsoluteExpiration' column. 
  • By any chance the value in 'ExpireAtTime' is greater than 'AbsoluteExpiration' value then the record will be an expired state because 'AbsoluteExpiration' value takes priority.
Run application and access this new endpoint where expirations specified explicitly and then check the cache table as below.

Fetch Cached Data From SQL Cache Table:

IDistributedCache interface provided methods like GetAsync, GetStringAsync to fetch data.

GetAsync - this method expects an input parameter, which is 'key' to query the cache database. This GetAsync method return Byte[] array of data where we need to explicitly convert that result to a string before serving the results to API clients.

GetStringAsync - this method expects an input parameter, which is 'key' to query the cache database. This GetStringAsync method returns the string directly to the API clients. Basically, cache data is in Byte[] format while retrieving from the database but this method implicitly converts those Byte[] of data to the string.
Note:
IDistributedCache interface also provides non async methods like Get, GetString , but async methods recomended.
Let's implement an endpoint to fetch the cached data as follow.
TestController.cs:
[Route("get-cache")]
[HttpGet]
public async Task<IActionResult> GetCache()
{
 string name = await _distributedCache.GetStringAsync("test2");
 return Ok(name);
}
Run the application and access the endpoint then look the result as follows.

Delete Cached Data:

IDistributedCache interface provided a method like RemoveAsync to delete the cached record from the cache table.

RemoveAsync - this method expects a 'key' as the input parameter, based on the 'key' value removes the record from the cache table.
Note:
IDistributedCache interface also provides non async method like Remove, but async methods recomended.
To test, create a sample endpoint to delete the cache data as below
TestController.cs:
[Route("delete-cache")]
[HttpGet]
public async Task<IActionResult> DeleteCache(string key)
{
 await _distributedCache.RemoveAsync(key);
 return Ok();
}

Configure SlidingExpriation Time Globally:

'AddDistributedSqlServerCache' service by default will configure SlidingExpiration time to 20 minutes. This time will get overridden if we use 'DistributedCacheEntryOptions' parameter in SetStringAsync or SetAsync methods.

To configure SlidingExpiration time globally and explicitly do as below.
services.AddDistributedSqlServerCache(options => {
 options.DefaultSlidingExpiration = TimeSpan.FromMinutes(10);
});
Here global default SlidingExpiration changed to 10 minutes.

Deleting Expired Items From Cache Table: 

'AddDistributedSqlServerCache' service by default configure with the option of deleting the expired cache records. It has an option like 'ExpiredItemsDeletionInterval' where it value by default assigned with 30 minutes. So if you want we can change it explicitly by assigning our own interval time.

If we are creating a cache item by using the SetStringAsync method without the 'DistributedCacheEntryOptions' parameter in this in our table 'AbsoluteExpiratin' column will be null.
So in this case after expiration on the 'ExpireAtTime' column, it will wait for 30  minutes and then deletes the record from the cache table.

If we are creating a cache item by using the SetStringAsync method with the 'DistributedCacheEntryOptions' parameter, in this case, we will 'AbsoluteExpriation' column with value. So after expiration on the 'AbsoluteExpiration' column, it will wait for 30 minutes and then deletes the record from the cache table.

Set 'ExpiredItemsDeletionInterval' as below
Startup.cs:
services.AddDistributedSqlServerCache(options => {
 options.ExpiredItemsDeletionInterval = TimeSpan.FromMinutes(6);
});
Here set deletion takes place after 6 minutes.

For 'ExpiredItemsDeletionInterval' there is constraint like its time should not be less than 5 minutes. If you try to set less the 5minutes application gives an error below.

Sample Code Caching Real Data:

For understanding purpose, created an endpoint for each IDistributedCache interface method. In real-time all methods mostly used inside of single endpoint based on its functionality.
GadgetController.cs:
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Caching.Distributed;
using SqlDistributedCache.API.Data;
using System.Threading.Tasks;
using Newtonsoft.Json;
using System.Linq;
using System.Collections.Generic;
using SqlDistributedCache.API.Entities;
using Microsoft.EntityFrameworkCore;
using System;

namespace SqlDistributedCache.API.Controllers
{
    [ApiController]
    [Route("[controller]")]
    public class GadgetController : ControllerBase
    {
        private readonly IDistributedCache _distributedCache;
        private readonly MyWorldDbContext _myWorldDbContext;
        public GadgetController(
            IDistributedCache distributedCache,
            MyWorldDbContext myWorldDbContext)
        {
            _distributedCache = distributedCache;
            _myWorldDbContext = myWorldDbContext;
        }

        [Route("get")]
        [HttpGet]
        public async Task<IActionResult> Get()
        {
            var cachedGadgets = await _distributedCache.GetStringAsync("myGadgets");
            if (!string.IsNullOrEmpty(cachedGadgets))
            {
                List<Gadgets> result = JsonConvert.DeserializeObject<List<Gadgets>>(cachedGadgets);
                return Ok(new {IsCache = true,result});
            }
            else
            {
                List<Gadgets> result = await _myWorldDbContext.Gadgets.ToListAsync();
                cachedGadgets = JsonConvert.SerializeObject(result);
                await _distributedCache.SetStringAsync("myGadgets", cachedGadgets, new DistributedCacheEntryOptions
                {
                    SlidingExpiration = TimeSpan.FromMinutes(30),
                    AbsoluteExpirationRelativeToNow = TimeSpan.FromMinutes(30)
                });
                return Ok(new {IsCache = false,result});
            }
        }

    }
}
For complete implementation check the below GitHub link.
Note:
It is recomended to use seperate database to have cache tables.

Wrapping Up:

Hopefully, this article will help to understand the .NET Core Distributed SQL Server Cache. I love to have your feedback, suggestions, and better techniques in the comment section.

Refer:

Follow Me:

Comments

Popular posts from this blog

Endpoint Routing In Asp.Net Core

How Routing Works In  Core 2.1 And Below Versions?: In Asp.Net Core routing is configured using app.UseRouter() or app.UseMvc() middleware. app.UseMvc(routes => { routes.MapRoute( name: "default", template: "{controller=Home}/{action=Index}/{id?}"); }); Here in Dotnet Core version 2.1 or below versions on the execution of route middleware request will be navigated appropriate controller matched to the route. An operation or functionality which is dependent on route URL or route values and that need to be implemented before the execution of route middleware can be done by accessing the route path from the current request context as below app.Use(async (context, next) => { if(context.Request.Path.Value.IndexOf("oldvehicle") != -1) { context.Response.Redirect("vehicle"); } else { await next(); } }); app.UseMvc(routes => { routes.MapRoute( name: "vehicleRoute", template: "vehicle", defaul

GraphQL API Integration In Asp.Net Core Application

Introduction: GraphQL is a query language for your API and a server-side runtime for executing queries by using a type system you define for your data. GraphQL can be integrated into any framework like ASP.NET, Java, NestJs, etc and it isn't tied to any specific database or storage engine and is instead backed by your existing code and data. How GraphQL API Different From Rest API: GraphQL exposes a single end-point or route for the entire application, regardless of its responses or actions. HTTP-POST is the only Http verb recommended by the GraphQL. The client applications (consumers of API) can give instructions to GraphQL API about what type of properties to be returned in the response. Building Blocks Of GraphQL API: The main building blocks of GraphQL API is Schemas and Types.  A 'Schema' in GrpahQL API describes the functionality available to the clients connect to API. Schema mostly consists of GraphQL Object Types, Queries, Mutations, etc. T

ASP.NET Core Web API Versioning

Introduction: An iteration and evolutionary changes of an ASP.NET Core Web API is handled by Versioning. Versioning of an API gives confidence to the clients which consumes API for a long time. Any changes or development of an API will be accessible using the new version and it won't cause issues to the clients consuming the old version of API. When To Use Versioning: Any API response changes. Developing an API by implementing testing levels like 'Alpha', 'Beta', and 'RC' versions before releasing Production. Deprecating an API which means API going to be removed or upgraded by a version within a short period. Versioning Types: Query String Versioning Url Path Versioning Media Type Versioning API Version Nuget: To Configure versioning to AspNet Core Web API Microsoft provided a library(Microsoft.AspNetCore.Mvc.Versioning). So to use the versioning library please install NuGet below.              Install-Package Microsoft.A

.NET Core MVC Application File Upload To Physical Location With Buffered Technique

Buffering Technique In File Upload: The server will use its Memory(RAM) or Disk Storage to save the files on receiving a file upload request from the client.  Usage of Memory(RAM) or Disk depends on the number of file requests and the size of the file.  Any single buffered file exceeding 64KB is moved from Memory to a temp file on disk.  If an application receives heavy traffic of uploading files there might be a chance of out of Disk or RAM memory which leads to crash application. So this Buffer technique used for small files uploading. In the following article, we create a sample for the file uploading using .NET Core MVC application. Create The .NET Core MVC Project: Let's create a .NET Core MVC project, here for this sample I'm using Visual Studio Code as below.   Check the link to use the Visual Studio Code for .NET Core Application . IFormFile: Microsoft.AspNetCore.Http.IFormFile used for file upload with buffered technique. On uploading files f

Ionic Picker Sample Code In Angular

Introduction: Ionic Picker(ion-picker) is a popup slides up from the bottom of the device screen, which contains rows with selectable column separated items. The main building block of ion-picker as follows: PickerController PickerOptions PickerController: PickerController object helps in creating an ion-picker overlay. create(opts?: Opts): Promise<Overlay> PickerController create method helps in create the picker overlay with the picker options PickerOptions: PickerOptions is a configuration object used by PickerController to display ion-picker. Single Column Ionic Picker: single.item.picker.ts: import { Component } from "@angular/core"; import { PickerController } from "@ionic/angular"; import { PickerOptions } from "@ionic/core"; @Component({ selector: "single-column-picker", templateUrl:"single.item.picker.html" }) export class SingleItemPicker { animals: string[] = ["Tiger&quo

Asp.Net Core MVC Form Validation Techniques

Introduction: Form validations in any applications are like assures that a valid data is storing on servers. All programing frameworks have their own individual implementations for form validations. In Dotnet Core MVC application server-side validations carried on by the models with the help of Data Annotations and the client-side validations carried by the plugin jQuery Unobtrusive Validation. jQuery Unobtrusive Validation is a custom library developed by Microsoft based on the popular library  jQuery Validate . In this article, we are going to learn how the model validation and client-side validation works in Asp.Net Core MVC Application with sample examples. Getting Started: Let's create an Asp.Net Core MVC application project using preferred editors like Microsoft Visual Studio or Microsoft Visual Studio Code. Here I'm using Visual Studio. Let's create an MVC controller and name it as 'PersonController.cs' and add an action method as bel

How Response Caching Works In Asp.Net Core

What Is Response Caching?: Response Caching means storing of response output and using stored response until it's under it's the expiration time. Response Caching approach cuts down some requests to the server and also reduces some workload on the server. Response Caching Headers: Response Caching carried out by the few Http based headers information between client and server. Main Response Caching Headers are like below Cache-Control Pragma Vary Cache-Control Header: Cache-Control header is the main header type for the response caching. Cache-Control will be decorated with the following directives. public - this directive indicates any cache may store the response. private - this directive allows to store response with respect to a single user and can't be stored with shared cache stores. max-age - this directive represents a time to hold a response in the cache. no-cache - this directive represents no storing of response and always fetch the fr

Blazor Server CRUD Operations

Introduction: Blazor Server is a web framework to develop server-side single-page applications. Blazor is made up of components with the combinations on C#, Html, CSS.  Blazor Server is production-ready from the .Net Core 3.0.  Blazor Server Working Mechanism: Blazor Server is a very light-weight web development framework.  In Blazor Server, not all code gets downloaded to the client browsers. Blazor Server made of components these components can be a block of code or page with respective navigation.  Blazor server application communicates with the server with a SignalR background connection which is inbuilt functionality. Application click,  form submission, change events, application page navigation every operation is carried out by the SignalR connection by communicating with the server.  Blazor updates the Html DOM very gently on every data update without any overhead. Blazor Server application maintains a nice intelligent tree structure to update the required inform

NestJS API CRUD Operations With MongoDB

Introduction: NestJS is a framework used to develop server-side applications. NestJS built on top of Node.js frameworks like Express. It is a combination of Progressive Javascript, Object-Oriented Programming, Functional Programming, and Functional Reactive Programming. Nest CLI Installation: Using Nest CLI we are able to generate the NestJS starter project with the default template. To install Nest CLI globally over our system open command prompt and run the command               npm i -g @nestjs/cli Now create a sample project by using Nest CLI command              nest new your_project_name package.json: Now open the package.json file from the sample application created, you can observe few properties like "scripts", "dependencies", and "devDependencies". "dependencies" contains all plugins to be installed and used them to run the application. "devDependencies" contain all plugins to be installed and used them

Blazor WebAssembly Dynamic Form Validation

Introduction: In Blazor WebAssembly(client-side framework) form validation can be done with Data Annotations. Using Data Annotations we can validate form either by default validation attributes or by creating custom validation attributes. Using this Data Annotation attribute we can dynamically add or remove validation on a specific field in a form. Create Blazor WebAssembly Project: To create a Blazor WebAssembly template project need to install the latest version of VisualStudio 2019 for rich intelligence support or we can use VisualStudio code but less intelligence support from the editor.  Click here to know about Blazor WebAssembly template creation. Blazor WebAssembly is in preview mode, not yet ready for production. Create Razor Component: After creating a sample project using the Blazor WebAssembly template, in "Pages" folder add new Razor Component , name it as "UserForm.razor" Add Route: In Blazor routing can be configured using @