Tag: Docker

Sitecore Asp.Net rendering with Content Resolver for Helix Examples Solution

In my previous post we saw how to create a simple rendering with data source.

For creating rendering using content resolver first follow the blog <<enter blog url here>>

Content resolvers help provice more complex data beyond the serialization of a component data source.

In this blog will list all the Articles on the page which are marked as Featured Article.

The custom logic for filtering will go in Content resolver.

Craete a project for Content Resolver(.net framework 4.8) . This framework is used just to follow with the exisitng content resolvers provided by Helix Examples Solution.

Content Resolver Project (BasicCompany.Feature.Articles.Platform)

Create a new .Net Framework project

Instead of creating new poroject I will copy the project from Navigation/Platform folder and rename it to BasicCompany.Feature.Articles.Platform.

Delete all the files from this project as it relates to Navigation. You may also want to change the AssemblyName and the AssemblyInfo file.

Create Models for Articles and Article

Create Models Folder and add below models

Articles.cs

using Sitecore.Data.Items;
using System.Collections.Generic;

namespace BasicCompany.Feature.Articles.Models
{
    public class Articles
    {
        public Item ArticlesPage { get; set; }

        public IList<Article> ArticleItems { get; set; }
    }
}

Article.cs

using Sitecore.Data.Items;

namespace BasicCompany.Feature.Articles.Models
{
    public class Article
    {
        public Item Item { get; set; }

        public Item ItemData { get; set; }
        public string Url { get; set; }
    }
}

Create Service for ArticleBuilder and ArticleRootResolver

Create a new folder Services and following-

//IArticleBuilder
 public interface IArticleBuilder
    {
        Articles.Models.Articles GetArticles(Item contextItem);
    }
//ArticleBuilder 

 public class ArticleBuilder : IArticleBuilder
    {
        private readonly IArticleRootResolver _articleRootResolver;
        private readonly BaseLinkManager _linkManager;

        public ArticleBuilder(BaseLinkManager linkManager, IArticleRootResolver articleRootResolver)
        {
            _articleRootResolver = articleRootResolver;
            _linkManager = linkManager;
        }

        public Articles.Models.Articles GetArticles(Item contextItem)
        {
            var articleRoot = _articleRootResolver.GetArticleRoot(contextItem);
            if (articleRoot == null)
            {
                return new Articles.Models.Articles();
            }

            return new Articles.Models.Articles()
            {
                ArticlesPage = articleRoot,
                ArticleItems = GetArticleItems(articleRoot, contextItem)
            };
        }

        private IList<Article> GetArticleItems(Item articleRoot, Item contextItem)
        {
            var items = new List<Item>();

            items.AddRange(articleRoot.Children.Where(item => item.DescendsFrom(Templates.ArticleItem.Id)));

            var articleItems = items.Select(item => new Article()
            {
                Item = item,
                ItemData = item.Axes.GetDescendants().FirstOrDefault(itemData => itemData.DescendsFrom(Templates.ArticleItemData.Id)),
                Url = _linkManager.GetItemUrl(item)
            }).ToList();

            return articleItems;
        }
    }
//IArticleRootResolver

 public interface IArticleRootResolver
    {
        Item GetArticleRoot(Item contextItem);
    }

namespace BasicCompany.Feature.Articles.Services
{
    public class ArticleRootResolver : IArticleRootResolver
    {
        public Item GetArticleRoot(Item contextItem)
        {
            if (contextItem == null)
            {
                return null;
            }
            return contextItem.DescendsFrom(Templates.ArticleRoot.Id)
                ? contextItem
                : contextItem.Axes.GetAncestors().LastOrDefault(x => x.DescendsFrom(Templates.ArticleRoot.Id));
        }
    }
}

Create Layout Service i.e. content resolver class

Create new folder LayoutServices and add following-

namespace BasicCompany.Feature.Articles.LayoutService
{
    public class ArticleContentResolver : Sitecore.LayoutService.ItemRendering.ContentsResolvers.RenderingContentsResolver
    {
        private readonly IArticleBuilder _articleBuilder;

        public ArticleContentResolver(IArticleBuilder articleBuilder)
        {
            _articleBuilder = articleBuilder;
        }

        public override object ResolveContents(Rendering rendering, IRenderingConfiguration renderingConfig)
        {
            var articles = _articleBuilder.GetArticles(this.GetContextItem(rendering, renderingConfig));

            var contents = new
            {
                ArticleItems = articles.ArticleItems.Select(item => new
                {
                    Item = item.Item,
                    ItemData = item.ItemData,
                    Serialized = base.ProcessItem(item.ItemData, rendering, renderingConfig)
                }).Select(article => new
                {
                    Url = LinkManager.GetItemUrl(article.Item),
                    Id = article.Item.ID,
                    Fields = new
                    {
                        Title = article.Serialized[article.ItemData.Fields["Title"].Name],
                        Description = article.Serialized[article.ItemData.Fields["Description"].Name],
                        ShortDescription = article.Serialized[article.ItemData.Fields["ShortDescription"].Name],
                    }
                })
            };

            return contents;
        }
    }
}

Create Service Configurator to register the services-

namespace BasicCompany.Feature.Articles
{
    public class ServicesConfigurator : IServicesConfigurator
    {
        public void Configure(IServiceCollection serviceCollection)
        {
            serviceCollection.AddTransient<Services.IArticleBuilder, Services.ArticleBuilder>();
            serviceCollection.AddTransient<Services.IArticleRootResolver, Services.ArticleRootResolver>();
        }
    }
}

Create Template Class

Change the Item ID’s as per your Sitecore Instance

namespace BasicCompany.Feature.Articles
{
  public static class Templates
  {
        public static class ArticleItem
        {
            public static readonly ID Id = new ID("{EE5CE126-890D-4F01-9DD5-3D81FC397A91}"); //
        }

        public static class ArticleItemData
        {
            public static readonly ID Id = new ID("{8AA19CA1-99A6-4588-B1D7-3FA9A8F6756A}"); //
        }

        public static class ArticleRoot
        {
            public static readonly ID Id = new ID("{A46A11C6-C7F9-4F61-BF0C-FFF060F0FECC}"); //
        }
  }
}

Create App Config to register the ServiceConfigurator-

Create Feature.Articles.config file in App_Config/Include/Feature folder

<?xml version="1.0"?>

<configuration xmlns:patch="http://www.sitecore.net/xmlconfig/">
  <sitecore>
    <services>
      <configurator type="BasicCompany.Feature.Navigation.ServicesConfigurator, BasicCompany.Feature.Navigation" />
    </services>
  </sitecore>
</configuration>

Create Templates for Article

These templates are used to indicate the different level s of Article. i..e Article Page- will inherit from _ArticleRoot, ArticlePage will inherit from _ArticleItem and Article Content will inherit from _ArticleItemData

Sitecore Items

Create Rendering Content Resolver

Create a New “Rendering Contents Resolvers Folder” in /sitecore/system/Modules/Layout Service

Craete a New “Rendering Contents Resolver” in this folder.

Provide the type – BasicCompany.Feature.Articles.LayoutService.ArticleContentResolver, BasicCompany.Feature.Articles

Create Articles Json Rendering

Craete a neJson rendering name “Articles” and newly created content resolver in the “Rendering Contents Resolver” field.

Add the new rendering to the page

Publish items

Rendering Project

Create Models Articles.cs

using Sitecore.AspNet.RenderingEngine.Binding.Attributes;
using Sitecore.LayoutService.Client.Response.Model.Fields;

namespace BasicCompany.Feature.Articles.Models
{
    public class Articles
    {
        [SitecoreComponentField]
        public ContentListField<Article> ArticleItems { get; set; }
    }
}

Create new view Articles.cshtml in /Views/Shared/Components/SitecoreComponent

@using Sitecore.AspNet.RenderingEngine.Extensions
@model BasicCompany.Feature.Articles.Models.Articles


<div class="container">
    <div class="product-list-columns columns is-multiline">
        @foreach (var article in Model.ArticleItems)
        {
            <partial name="_ArticleList" model="article" />
        }
    </div>
</div>

Create _ArticleList.cshtml in Views/Shared folder

Note its using ItemLinkField

@model ItemLinkField<Article>

<a href="@Model.Url" class="column product-list-column is-4-desktop is-6-tablet">
    <div class="card">
        <div class="card-content">
            <div class="content">
                <h4 asp-for="@Model.Fields.Title"></h4>
                <p asp-for="@Model.Fields.ShortDescription"></p>
            </div>
        </div>
    </div>
</a>

Update the RenderingEngineOptionsExtensions

namespace BasicCompany.Feature.Articles.Extensions
{
    public  static class RenderingEngineOptionsExtensions
    {
        public static RenderingEngineOptions AddFeatureArticle(this RenderingEngineOptions options)
        {
            options

                .AddModelBoundView<Article>("Article")
                .AddModelBoundView<Models.Articles>("Articles");
            return options;
        }
    }
}

Update Articles.modules.json to serialiaze content resolver

{
  "namespace": "Feature.Articles",
  "items": {
    "includes": [
      {
        "name": "templates",
        "path": "/sitecore/templates/Feature/Articles"
      },
      {
        "name": "renderings",
        "path": "/sitecore/layout/Renderings/Feature/Articles"
      },
      {
        "name": "contents-resolvers",
        "path": "/sitecore/system/Modules/Layout Service/Rendering Contents Resolvers/Articles"
      }
    ]
  }
}

IMP – Ensure the Startup.cs has AddFeatureArticle() added in AddSitecoreRenderingEngine

Output

List of Articles-

When we click on any of the Article take to the Article page-

The above pages are shown as per this structure in Sitecore

Configure Sitecore Content Serialization for ASP.Net Rendering with Helix Examples Solution

In this blog will creata a new component name Article in the Helix Examples Solution to demonstrate how to configure and use Sitecore Content Serlialization (SCS).

Assuming the Sitecore CLI is installed along with Sitecore.DevEx.Extensibility.SerializationSitecore.DevEx.Extensibility.Publishing plugins are installed.

For more details on the plugin installation please see this link- https://doc.sitecore.com/xp/en/developers/101/developer-tools/install-sitecore-command-line-interface.html

Open the helix-basic-aspnetcore folder in Visual Studio and see Sitecore.json file. This file has the configuration settings for SCS.

modules – willl look into the src folder for *.module.json file for any component specific configuration the items that need to be serialized.

So lets create a new module or rendering feature named “Articles”. Just a folder and not a project itself

1. Create a module json for serlialization configuration

IMP – Create Articles.module.json file in the project root folder

Add following to the json file-

{
  "namespace": "Feature.Articles",
  "items": {
    "includes": [
      {
        "name": "templates",
        "path": "/sitecore/templates/Feature/Articles"
      },
      {
        "name": "renderings",
        "path": "/sitecore/layout/Renderings/Feature/Articles"
      }
    ]
  }
}

Here the items that will be serliazed are templates and rendering from the given path in Sitecore to the local Solution Folder configured in Sitecore.json file the path mentioned in defaultModuleRelativeSerializationPath property. See step 1

IMP- Ensure the module file is in Articles folder. Your project folder should looks like this-

2. Create a Sitecore Template and Rendering for Articles

Create a Json Rendering for now(fill in the details later)

3. Sync the items (manual)

Execute following command to serlaize the items for Articles-

dotnet sitecore ser pull

Project folder should now have items folder with templates and rendering-

Thats it any Templates and rendering created for Articles (new component) should be serliazed.

Refer BasicCompany.module.json for any placeholders, layouts etc serlization at the project level.

Hope this helps.

Create a Asp.Net simple rendering using data source in Helix Examples Solution

In this blog will create a simple rendering uing Asp.Net Rendering SDK in Helix Examples Solution

Please refer the blog to create a rendering folder and configure the SCS before proceeding this blog.

So lets create a new module or rendering feature named “Articles”.

1. Create a Feature project using Razor Class Library

Project Name – BasicCompany.Feature.Articles.Rendering

Notice the project path

Choose .Net Core 3.1 Framework-

Delete any exisitng files and folders under this project-

Edit the project to use netcoreapp3.1 and AddRazorSupportForMvc to true

Rename helix-basic-aspnetcore\src\Feature\Articles\BasicCompany.Feature.Articles.Rendering to rendering. Just to follow other feature fodler structure.

2. Install Sitecore packages

Sitecore.AspNet.RenderingEngine

Sitecore.LayoutService.Client

I have installed verions 16 just to be in sync with other projects. You may install the latest.

New rendering project should have these packages installed-

Remove these packages as this may be not required at thi point of time or downgrade this to 3.1.1

Refer the new created rendering project to BasicCompany.Project.BasicCompany.Rendering

When the solution is build you may see this error-

Severity Code Description Project File Line Suppression State
Error The package reference ‘Sitecore.AspNet.RenderingEngine’ should not specify a version. Please specify the version in ‘C:\projects\Helix.Examples\examples\helix-basic-aspnetcore\Packages.props’ or set VersionOverride to override the centrally defined version. BasicCompany.Feature.Articles.Rendering C:\projects\Helix.Examples\examples\helix-basic-aspnetcore\src\Feature\Articles\rendering\BasicCompany.Feature.Articles.Rendering.csproj

Solution– Remove the version for the plugin fropm project file

Edit the project file and remove version from the PackageReference-

Solution should build successully.

3. Ensure Articles.modules.json file in Feature folder

Please see this blog <<Enter blog url here>> how to create a module.json file to serliaze the Sitecore items for new Feature.

4. Create required Sitecore Templates, content, renderings and Placeholder Settings

Template – Article in following path- /sitecore/templates/Feature/Articles

Page Type Template – Create 2 page type templates “Articles” and “Article” page as below.

Add any required Insert Options where necessary.

IMP- inherit from _NavigationItem to display the Articles as Navigation option

Enter Navigation Title for Articles page-

Content

Create content in Home page based on the Article templates created.

Rendering

Create a new Json Rendering Article. See previous post

Set Datasource Location- ./Page Components|query:./ancestor-or-self::*[@@templatename=’Site’]/Shared Content/Articles

Datasource Template- /sitecore/templates/Feature/Articles/Article

Add rendering to Template

Add Header, Article and Footer Controls to the Presentation

Select appropriate datasource for the Article component-

You can also add the component from experience editor. For simplicity purpose I am adding this from the presentation details manually.

Publish the changes and see https://www.basic-company-aspnetcore.localhost

Note:- If you get bad gateway error the resolution is in this blog <<blog for resolution>>

you should see the Articles option in Navigation-

Note- We wont be configuring “Articles” page in this blog. Will see that in next blog when uing Content Resolver.

See thie Article page-

https://www.basic-company-aspnetcore.localhost/Articles/Sitecore%20Content%20Serialization%20structural%20overview

There is a error – “Unknown component ‘Article'”. This is because we havent yet created view for this component.

Create Model in BasicCompany.Feature.Articles.Rendering project for rendering Article component

Note the propeties are using Sitecore.LayoutService.Client.Response.Model.Fields

using Sitecore.LayoutService.Client.Response.Model.Fields;
using System;
using System.Collections.Generic;
using System.Text;

namespace BasicCompany.Feature.Articles.Rendering.Models
{
    public class Article
    {
        public TextField Title { get; set; }

        public RichTextField Description { get; set; }

        public TextField ShortDescription { get; set; }
    }
}

Create View in BasicCompany.Feature.Articles.Rendering project for rendering Article component

Create Article.cshtml file under Views/Shared/Components/SitecoreComponent

Add following markup-


@model Article

<div class="container">
    <section class="hero is-small product-detail-hero">
        <div class="hero-body">
             <h3  class="title" asp-for="Title"></h3>
            <sc-text class="subtitle is-one-quarter" asp-for="Description"></sc-text>
        </div>
    </section>
</div>

InViews Folder create _ViewImports.cshtml file and put the following in file-

@using Sitecore.LayoutService.Client.Response.Model
@using Sitecore.LayoutService.Client.Response.Model.Fields
@using Sitecore.AspNet.RenderingEngine.Extensions
@using BasicCompany.Feature.Articles.Rendering.Models

@addTagHelper *, Microsoft.AspNetCore.Mvc.TagHelpers
@addTagHelper *, Sitecore.AspNet.RenderingEngine

Add Extensions for registering the ModelBoundView. This is a static class and will be used in Project Rendering on application startup (BasicCompany.Project.BasicCompany.Rendering).

using BasicCompany.Feature.Articles.Rendering.Models;
using Sitecore.AspNet.RenderingEngine.Configuration;
using Sitecore.AspNet.RenderingEngine.Extensions;

namespace BasicCompany.Feature.Articles.Extensions
{
    public  static class RenderingEngineOptionsExtensions
    {
        public static RenderingEngineOptions AddFeatureArticle(this RenderingEngineOptions options)
        {
            options
                .AddModelBoundView<Article>("Article");            
            return options;
        }
    }
}

In BasicCompany.Project.BasicCompany.Rendering project, Startup.cs register the component-

Build the Project

Output– https://www.basic-company-aspnetcore.localhost/Articles/Sitecore%20Content%20Serialization%20structural%20overview

Issues

Bad gateway error while accessing – https://www.basic-company-aspnetcore.localhost/

Solution-

Restart the rendering container

docker ps
docker restart <<rebdering container>>

Debug Helix Examples solution using Asp.Net Rendering hosted in Docker Containers

See this blog to setup the development environment for Helix Examlpes using Docker

Open the solution from following location – \examples\helix-basic-aspnetcore

Open the containers tab and should list all the containsers with its status-

You may also use following command to check the status of contrianers-

docker ps

Lets debug the Navigation which has content resolver-

Right click the CD container and Attach to Process

Select Managed(.Net 4.x) debug type. Select w3wp.exe and click Attach.

Helix Examples Solution should now run in debug mode.

Build the solution, add a breakpoint to any of the resolvers (Header or Footer)

Refresh or visit the site – https://www.basic-company-aspnetcore.localhost/ and should be able to see the debugger-

Issues debuging or just building the solution-

Bad Gateway-

Solution- You may see the errors with command-

docker-compose logs -f rendering

Following log appears- binary is being used by another process. This is the issues with the dotnet watch with the docker

Solution- Restart the rendering container

This should bring up the site.

You can also watch the changes outside the docker. See here for more details-

https://sitecore.stackexchange.com/questions/29566/asp-net-core-rendering-sdk-every-time-i-have-to-run-docker-compose-restart-ren

Sitecore Headless Development with ASP.NET Rendering SDK – Helix Examples Solution – The Docker Way

This blog will give a quick overview of setting development environment for Headless Development with ASP.Net Rendering SDK using the Helix Examples and the docker.

Although there are videos and blogs around same I will do a quick walk through on setting Helix Examples and any errors I faced whilst setting up the environment.

Refer the following for same – https://github.com/Sitecore/Helix.Examples/tree/master/examples/helix-basic-aspnetcore

Install .Net Core 3.1

https://dotnet.microsoft.com/en-us/download/dotnet/3.1

Install .Net core 3.1 on your machine and this is required to create any rendering or platform projects later to extend the Helix Examples Solution or compiling the existing code.

Install Docker Desktop on Windows

https://docs.docker.com/desktop/windows/install/

Run this on Hyper-V mode and Switch to Windows Containers

Install Visual Studio Code and Visual Studio 2022 Community Edition

https://visualstudio.microsoft.com/vs/community/

https://code.visualstudio.com/download

Whilst installing Visual Studio 2022 select the .Net Framework project and templates option as the platform projects uses .Net Framework 4.8 version. This will also help further if you want to extend the solution.

Install and Configure Windows Terminal (optional)

https://docs.microsoft.com/en-us/windows/terminal/install

https://dev.to/shahinalam02/customize-your-terminal-using-oh-my-posh-theme-38if

https://www.hanselman.com/blog/my-ultimate-powershell-prompt-with-oh-my-posh-and-the-windows-terminal

Install Windows Terminal, refer above link and if you fancy applying the themes, although this is optional.

Install git

https://git-scm.com/download/win

Clone Helix Examples Solution

https://github.com/Sitecore/Helix.Examples

https://github.com/Sitecore/Helix.Examples.git

Initialise the config

Navigate to \examples\helix-basic-aspnetcore and run following-

.\init.ps1 -LicenseXmlPath C:\<<path to license>>\license.xml -SitecoreAdminPassword "b"

This should initalise teh .env file and fill in the values of the variables for License and Admin Password. Also it will populate other variables.

Build Images

Once the config are initialised run folowing command-

up.ps1

Once all the images are downloaded and built along with solution login to CM should will be asked.

Login to the CM and Allow access to Sitecore API and Offline Access

Once this done the CD and CM app should be ready along with the data been synched.

Check the logs for any errors in rendering with following command-

docker-compose logs -f rendering

Access Application

Site can be accessed with the following url –

Sitecore Content Management: https://cm.basic-company-aspnetcore.localhost/sitecore/

Sitecore Identity Server: https://id.basic-company-aspnetcore.localhost

Basic Company site: https://www.basic-company-aspnetcore.localhost

Use following to stop/remove containers-

docker compose down

Issues while building the images

Error response from daemon: Unrecognised volume spec: file ‘\\.\pipe\docker_engine’ cannot be mapped. Only directories can be mapped on this platform

Solution-

Disable Docker Compose V2 using command or in Docker Desktop-

docker-compose disable-v2

or Uncheck the “Use Docker Compose V2” option

https://stackoverflow.com/questions/68010612/error-response-from-daemon-unrecognised-volume-spec-file-pipe-docker-engi

Dockerfile Best Practice

Build Modular Images i.e. Decouple applications

Create a seperate image for each application. Containers can talk to each other and can form a single large application and helps to scale each application

Don’t sotre data in Images

Images are read-only layer. When a container or image is deleted the data is lost

Use Cache Busting strategy

Install the repositories and packages together. As the docker file ises layered architecture having a seperate command for updating repositories and packages may not gurantee the repsoitories will be upto date and may result in dependency issue.

Use Version Pinning

When installing packages specifiy which version you want to install as everytime the image is build it will install the latest package where a application may not be compatible. Version pinning will always ensure the image will have specific version which your application supports.

Create slim images

This will help pull the images from which ever repository you are using quickly

Install only necessary or required packages

This will make image slim or with minimal packages and no unwanted packages are installed so every time image is build with minimal packages the build is fast and light weight. Also the containers created from such images are light weight and fast.

Maintain different images for different environements

Development images may contain debug tools and temprorary files required for debugging and bulding your application. However there tools are not required for production images. Hence remvoe any temporary files/folder and such tools for prodcution by creating a seperate image for different environments.

Use multi-stage builds to create images

Multi-stage build helps to or uses multiple FROM statements where each FROM instruction can use a different base, and each of them begins with new stage of the build and everything that is required for application is in the final image leaving behind unwanted files. This will avoid executing any script that was done traditionaly.

Exclude any unwanted files and folders using .dockerignore file

Use .dockerignore to exlcude any unwanted files and folders e.g.:- temp folder etc. this make the image lighter.

Use CMD instructions to run software in Image

Use CMD instructions to run the software contained in your image along with arguments. CMD should be used in JSON format that is the command and parameters should be seperated by comma.

Minimize build times

By avoiding to send unwanted files to the build context using .dockerengine

References –

https://docs.docker.com/develop/develop-images/multistage-build/

https://docs.docker.com/develop/develop-images/dockerfile_best-practices/

Use Docker Image offline with Save and Load command in Ubuntu

Docker Save and Load command

At times if you dont want to always pull the image from image registry which takes time to pull if the image’s are heavy, it makes sense to save the image and use it offline. This avoids to always pull the image from the registry.

Save the image once into tar file and reuse the images.

To Save image use follwoing command

First pull the image from repository

docker pull httpd
docker image save httpd -o httpdimage.tar

Get the image from the tar file instead pulling it from the registry

docker image load -i httpdimage.tar

Docker Restart Policies

To setup restart policy to the container, use following command-

docker run --restart=<<policy option>> <<container>>

Following are the options for the container restart-

  1. no (default)
  2. on-failure
  3. always
  4. unless-specified

Following is the matrix for the restart policies-

* – this will start when the Docker daemon is started

Above is applicable if the container starts successfully

Live Restore

If you want to keep container running if the Docker daemon crashes or stops use the live restore option. This reeduces the container downtime due to daemon crashes or planned outages or upgrades.

Update the /etc/docker/daemon.json in Ubuntu system and add option live-restore:true

Cache Busting and Version Pinning when building Docker images

docker file – Layered Architecture

Docker uses Layered Architecture. When using Docker files it creates a new layer in the image which adds additional space to the image based on the instructions for that layer.

When a Docker build command is run it proceeds from the first instruction in Docker file to the last while caching each stage so as if the build fails next time build uses cache until it ran succesully and invalidated the stage that failed and the following stage. Layers repurpose the previous layers and don’t have to build all of them again.

In below example Docker file has 6 stages. Each stage will be cached when build command is ran.

Suppose a build fails at Stage 3 due to some reason or new package has to be added the Docker will invalidate the Stage 3 and the following stages

Next time when a issue is rectified the build command will repurpose the previuos layers and build the failed stages

docker file – Layered Architecture

But in this case the repository will not be update, so how to resolve or update the repository with the packages-

Cache Busting

In this case we can to combine the instructions so the repository is updated along with packages as below

docker file – Cache Busting and Version Pinning

Merging Stage 2 and Stage 3 from the previous docker file in to single instruction will ensure the repository is first udpated and pakages are installed

Merging these stages is called as Cache Busting

Version Pinning

You can also explicity mention the version of package to be installed

In stage 2 docker file is instrcuting to install python3-pip 21.3.1 version

Best Practice-

Instructions which are most frequently modified should be at the bottom of the file and the instructions which are least modified should be at the top of the docker file