Continuous delivery with Azure App Service

Update:

Click here for the SoCalCode camp presentation about this topic.

Introduction

This post would introduce you to continuous delivery pipeline using Azure app services. We would take a use case and implement the steps that we need to take in order to establish a build pipeline.

What is Continuous Delivery?

In simple words “Constantly develop, automatically build and automatically deploy”. This means that as soon as code is checked in a system would automatically build the application and deploy.

Azure App Services

Azure app services is a set of technologies that enable development of cloud centric Web Apps, Mobile Apps, API Apps and Logic Apps. There is a great introduction to App Services presented at: https://azure.microsoft.com/en-us/documentation/articles/app-service-value-prop-what-is/ .

Power of App Services

To understand the power of Azure App Service you have to compare to a classic Web Application with any of the technology such as Azure App Service Web App. In a classic Web App, a web server such as IIS is the main component. The Web App is installed on IIS and the pages are served through IIS to internet audience. This is a typical on premises infrastructure implementation. You are responsible for managing the security, availability, scale and instrumentation. Part of the classic web app infrastructure is the responsibility of not only delivering the web app but maintenance of the web server. This includes the separation of environments such as development site, QA site, UAT site and the production site. Also, since web server maintenance is part of this infrastructure, you have to also think about the actual server where that web server is installed. The environment that server offers greatly effects how the web server would work. This is another layer of responsibility that a web developer has to keep in mind.

With the App Services, the IIS part has been abstracted away. This means that management of web server (for example IIS) is not the focus but the focus is the delivery of web app. As an application developer we can easily create on App and have it hosted in different deployment slots. These deployment slots makes it easy to create environments such as development site, QA site, UAT site and production site for the same web app.

Continuous delivery pipeline for Azure App Service

Since web server and the server hosting the web server is not part of Azure App Service, the establishment of continuous delivery pipeline is very easy to establish.

Our focus for this post is to list the steps and design patterns that we can use to establish the continuous delivery pipeline.

There are three major steps to establishment of continuous delivery pipeline for Azure App service. These are:

Establishment of development slots

Once you have created an Azure Web App, you have to define its deployment slots. Usually the deployment slots are representation of your different environments. For example, in a typical web development effort you would have following environments:

1.      Development: This is the environment that is used by development team to help them develop different aspects of the project. Typically this is referred simply as “dev”.

2.      QA: This environment is used by the QA team to test the web app separate from the development environment. This is great for providing isolation and also to do better validation testing. Typically this is simply referred as “qa”.

3.      UAT: This environment is used by product owners or stake holders to validate different features after the QA has signed off. Again an isolation from dev and QA allows the UAT to test the web app irrespective of the test data that QA has used to valid. Typically this is simply referred as “uat”. Usually a separate database is attached for the UAT environment.

4.      Staging: This sometimes also known as pre-production. Typically is used to validate the build process and once the build is validated, this environment is swapped with production. Usually the staging environment uses the same production database. This allows the swapping from staging to production seamless without any down time. Typically this is simply referred as “staging”.

5.      Production: This is the actual web application that represents the production environment. Typically this is simply referred as “prod”.

The Azure App Service gives each deployment slot a unique URL. This essentially means that each of the deployment slot is a separate web application. Each of the web app URL representation of the environment is used by different team members. Development team members use the dev URL, QA uses the QA URL, and UAT uses the UAT URL for the web app.

Here is an example of different deployment slots for our API web app.

Establishment of branching strategy

There are a lot of different branching strategies that are used in the industry. The branching strategy is designed or sometimes evolved based on respective objectives. One of those objectives is the environment. What it means is that for different environments different braches are established. To simplify let us take the following branching strategy.

Master branch – For Development environment

QA Branch – For QA and UAT environments

Production – For staging environment

Importance of branching strategy means for continuous delivery

Since the main tenant of continuous delivery system is to automatically we build and automatically from a code check in, we have to pay extra attention to where the code check in takes place. If we look at our branching strategy, it would mean that if we check in the code in the master branch then dev environment should be build. If we check in the QA branch then it means that QA and UAT environments would be build. Same goes for the staging environment. This is why your branching strategy should be representative of your build environments. Let us take a typical scenario to explain more:

Joe (Backend developer) completes first part of the story and checks in the code to master branch. This kicks off a fresh “dev” build.

Jessica (Front end developer) completes the second part of the story and checks in the code. This kicks off another fresh “dev” build. Since the second part of the story completes the story. The build manager merges the master branch into QA branch. This kicks off a QA build and a UAT build for both QA and UAT team members.

Establishment of build/publish process

Azure App Service deployment

There are multiple ways to deployment apps on Azure App Service.  There are:

FTP

This is a most direct and classical way of deploying any web app. The major drawback is that this a total manual process. If you need to automate this, you have to write quite complex scripts.

Web Deploy

This tool allows you to directly deploy web apps to azure app service from visual studio. Although you do not have to use FTP for this scenario but you still have to do actual deployment manually.

Kudu

This build engine is used where we want to have automatic build/publish execution when a source code repository is attached. This means that as soon as a check in take place on a branch (established in step 2), the kudu build process would kick in a do the rest.

Code checked-in to repository  >>  Kudu initiates the build >> Kudu publishes the website

Multiple web apps challenge

The above mentioned steps would work great if you have only one web app in your code repository. For example, you have create a dedicated branch for one web app that has one solution file (.sln). The challenge comes in the shape of a scenario where you have multiple web apps and they all share the same code repository. For example, in a typical business application, you might have one web app that serves the pages and one Web Api app that is consumed by the web app. You might have different release pipeline for WebApi and web App. In this scenario the visual studio solution would contain both projects as part of the solution.

To accommodate the scenario of multiple web apps projects in a solution, you have to take some extra steps.

Step 1. Add app setting to your App Service to uniquely identify your app. This is to give Kudu a way to kick start the build and complete the publishing once code has checked in.

Step 2. Add “.deployment” file to the base of your source code repository. The “.deployment” file gives Kudu a starting point to start the deployment process. Here is a sample:

As you can see what the “.deployment” file is asking Kudu to do is just to call deploy.cmd file. We would look at this in next step.

NOTE: 

Before proceeding further it is important to note that following are prerequisites for the next steps:
1. Nodejs: https://nodejs.org/en/

2. azure-cli: https://azure.microsoft.com/en-us/documentation/articles/virtual-machines-command-line-tools/

Step 3. Create deploy.cmd file. This is the file that would tell Kudu how many different web apps or web Api apps are available in your code base that needs to be built as part of continuous integration pipeline. 

Here is an example of deploy.cmd file:

If you look at this file, you would notice that there are three web apps that are mentioned in the code. These are the three projects that are part of same solution file. What this code is doing is checking which App Service has kicked started the build process. This essentially means the branch where the code check in has happened. The SITE_FLAVOR comes very handy here as we use this App setting to identify the application.

After the app service identification, the deploy.cmd is just calling the corresponding individual deployment files. In our examples there we have three different deployment files. Those are:

deploy.customersapi.cmd

deploy.customersweb.cmd

deploy.anotherapi.cmd

In our next step we would see how you create these individual deployment files.

Generating Deploy.customer.cmd

 Step 1:

Assuming that your customerapi’s project file is at c:\sites\CustomerApi\src\CustomerApi.csproj and customerapi’s solution file is at c:\sites\CustomerApi\src\CustomerApi.csproj and c:\sites\CustomerApi\CustomerApplication.sln. Execute the following command using elevated Administrator mode either on command prompt or Powershell prompt. I always prefer PowerShell because of ease use.

azure site deploymentscript --aspWAP c:\sites\CustomerApi\src\CustomerApi.csproj  -s c:\sites\CustomerApi\CustomerApplication.sln

      Step 2:

Running the above command would yield a file called deploy.cmd. Rename file deploy.cmd to deploy.customersapi.cmd.

Step 3:

Repeat steps 1 and 2 for customersweb and anotherapi projects.

Conclusion

Azure App services are set of very powerful technologies that gives a very clear pathway to establish a continuous delivery pipeline.

SocalCode Camp presentation

The following presentation about this topic presented at the 2016 SocalCode camp.

Continuous delivery with azure app service from Nabeel Khan