Deploy a Geo-redundant Web App behind an Azure Traffic manager using an ARM template.

This blog will guide you on how to deploy a Web App, App service plan in different geographical locations using Azure Traffic Manager to provide Geo redundancy.  I will discuss these concepts below and provide the necessary steps to achieve this .

We will familiarize ourselves with the terminology and the technologies which will be used in the blog to build out our solution:

  1. Azure APP Services
  2. Azure App Service plan
  3. App Service Editor
  4. Traffic Manager

 

1.Azure App Services

Azure App Service is a fully managed computing platform within the Azure environment that is optimized for hosting web apps, REST APIs, and mobile back ends. This Platform as a Service (PaaS) offereing allows you to focus on the app content side of things while Azure takes care of the infrastructure to run and scale your applications.

Azure App Services offers different pricing tiers to suit your needs

TierOffering
Free planUse this offering to implement a proof-of-concept
Shared planThis option is suitable for basic Web applications or static websites
Basic planUse this option for development/test environments
Standard planUse this option for Web and mobile applications in the production environment
Premium planThis is the recommended option for enterprise scale and integration
Isolated planThe Isolated service plan is designed to run mission-critical workloads that are required to run in a virtual network. The Isolated plan allows customers to run their apps in a private, dedicated environment in Azure

 

2. Azure App Service plan

An App Service plan is a set of physical resources and capacity available to deploy App Service apps. Web apps, mobile apps, and API apps hosted in Azure App Service, as well as Azure Functions, all run in an App Service plan. While you can deploy an unlimited number of applications into an App Service plan, the number you use greatly depends on the types of applications deployed and their required resources in CPU utilization.

An App Service Plan, at a very high level is the container in which web applications run. It is used to determine the resources available to your application and their boundary. There are a few categories of pricing tiers:

 

Compute TierOffering
Shared ComputeFree and Shared, the two base tiers, runs an app on the same Azure VM as other App Service apps, including apps of other customers. These tiers allocate CPU quotas to each app that runs on the shared resources, and the resources cannot scale out
Dedicated computeThe Basic, Standard, Premium, and PremiumV2 tiers run apps on dedicated Azure VMs. Only apps in the same App Service plan share the same compute resources. The higher the tier, the more VM instances are available to you for scale-out
IsolatedThis tier runs dedicated Azure VMs on dedicated Azure Virtual Networks, which provides network isolation on top of compute isolation to your apps
ConsumptionThis tier is only available to function apps. It scales the functions dynamically depending on workload. For more information, see Azure Functions hosting plans comparison

 

3.App Service Editor

App Service Editor is a web-based editor for App Service. This is great tool for deploying websites and editing HTML, CSS, JavaScript, jQuery, Angular JS or any client-side scripting effectively. Also, any edits to the file are auto saved and changes are reflected on the fly to the App service URL.

 

4.Traffic Manager

Azure Traffic Manager is a DNS-based traffic load balancer that enables you to distribute traffic optimally to services across global Azure regions, while providing high availability and responsiveness. The high availability works by monitoring the internet facing endpoints.

Traffic Manager uses DNS to direct client requests to the most appropriate service endpoint based on a traffic-routing method and the health of the endpoints. Traffic Manager provides a range of traffic-routing methods and endpoint monitoring options to suit different application needs and automatic failover models.

Azure Traffic Manager supports six traffic-routing methods to determine how to route network traffic to the various service endpoints. The following traffic routing methods are available in Traffic Manager

 

Routing MethodsDescription
PrioritySelect this method when you want to use a primary service endpoint for all traffic and provide backups in case the primary or the backup endpoints are unavailable
WeightedSelect this option when you want to distribute traffic across a set of endpoints, either evenly or according to weights, which you define on the profile
PerformanceSelect this option, when you have endpoints in different geographic locations, and you want end users to use the “closest” endpoint in terms of the lowest network latency
GeographicSelect this option, so that users are directed to specific endpoints (Azure, External, or Nested) based on which geographic location their DNS query originates from. This empowers Traffic Manager customers to enable scenarios where knowing a user’s geographic region and routing them based on that is important
Multi-valueSelect it for Traffic Manager profiles that can only have IPv4/IPv6 addresses as endpoints. When a query is received for this profile, all healthy endpoints are returned.

NOTE: At the time of writing, this method is supported only for external endpoints

SubnetThis traffic-routing method maps set of end-user IP address ranges to a specific endpoint within a Traffic Manager profile. When a request is received, the endpoint returned will be the one mapped for that request’s source IP address. This method is supported for public IP address as target

There are several ways you can create a web app including

  • Azure portal
  • Azure CLI
  • ARM Template
  • From an Integrated Development Environment) (IDE)

We will use an ARM Template to deploy our solution because it is a simple way to include all components in one go.

 

The template below will deploy an Azure App Service plan in two different locations (Australia East and Southeast Asia) in an array. The Array in the ARM template will be deployed based on the input location defined in template.

The ARM Template has three resources:

  • Azure APP Service Plan (Microsoft.Web/serverfarms)
  • Azure Web App (Microsoft.Web/sites)
  • Azure Traffic Manager (Microsoft.Network/trafficManagerProfiles)

Modify these settings in the ARM template to suit your needs:

  1. Add additional locations in the parameters section under If you add more locations, add endpoints in Traffic manager resources
  2. Choose App service plan in the parameters section farnSkuName
  3. Choose web app name in the parameters section webAppNamePrefix

The ARM template below is based on the web app deployed in two locations.

{
“$schema”: “http://schema.management.azure.com/schemas/2015-01-01/deploymentTemplate.json#”,
“contentVersion”: “1.0.0.0”,
“parameters”: {
“webAppNamePrefix”: {
“type”: “string”,
“minLength”: 1,
“defaultValue”: “kloudwebapp”
},
“farmSkuName”: {
“type”: “string”,
“defaultValue”: “S1”,
“allowedValues”: [
“F1”,
“D1”,
“B1”,
“B2”,
“B3”,
“S1”,
“S2”,
“S3”,
“P1”,
“P2”,
“P3”,
“P4”
],
“metadata”: {
“description”: “Describes plan’s pricing tier and capacity. Check details at https://azure.microsoft.com/en-us/pricing/details/app-service/”
}
},
“webAppLocations”: {
“type”: “array”,
“defaultValue”: [ “Australia east”, “Southeast Asia” ]
}
},
“variables”: {
},
“resources”: [
{
“name”: “[concat(parameters(‘webAppNamePrefix’),’-‘,copyIndex())]”,
“type”: “Microsoft.Web/serverfarms”,
“location”: “[parameters(‘webAppLocations’)[copyIndex()]]”,
“apiVersion”: “2015-08-01”,
“copy”: {
“count”: “[length(parameters(‘webAppLocations’))]”,
“name”: “farmCopy”
},
“sku”: {
“name”: “[parameters(‘farmSkuName’)]”
},
“dependsOn”: [],
“tags”: { },
“properties”: {
“name”: “[concat(parameters(‘webAppNamePrefix’),’-‘,copyIndex())]”,
“numberOfWorkers”: 1
}
},
{
“name”: “[concat(parameters(‘webAppNamePrefix’),’-site-‘,copyIndex())]”,
“type”: “Microsoft.Web/sites”,
“location”: “[parameters(‘webAppLocations’)[copyIndex()]]”,
“apiVersion”: “2015-08-01”,
“copy”: {
“count”: “[length(parameters(‘webAppLocations’))]”,
“name”: “siteCopy”
},
“dependsOn”: [
“farmCopy”
],
“tags”: {},
“properties”: {
“name”: “[concat(parameters(‘webAppNamePrefix’),’-site-‘,copyIndex())]”,
“serverFarmId”: “[resourceId(‘Microsoft.Web/serverfarms’, concat(parameters(‘webAppNamePrefix’),’-‘,copyIndex()))]”
}
},
{
“name”: “[concat(parameters(‘webAppNamePrefix’),’-tm-‘,uniqueString(resourceGroup().id))]”,
“type”: “Microsoft.Network/trafficManagerProfiles”,
“apiVersion”: “2015-11-01”,
“location”: “global”,
“dependsOn”: [
“siteCopy”
],
“properties”: {
“profileStatus”: “Enabled”,
“trafficRoutingMethod”: “Performance”,
“dnsConfig”: {
“relativeName”: “[concat(parameters(‘webAppNamePrefix’),’-tm-‘,uniqueString(resourceGroup().id))]”,
“ttl”: 30
},
“monitorConfig”: {
“protocol”: “HTTP”,
“port”: 80,
“path”: “/”
},
“endpoints”: [
{
“name”: “[concat(parameters(‘webAppNamePrefix’),’-endpoint-‘,’0’)]”,
“type”: “Microsoft.Network/trafficManagerProfiles/azureEndpoints”,
“properties”: {
“targetResourceId”: “[resourceId(‘Microsoft.Web/sites/’,concat(parameters(‘webAppNamePrefix’),’-site-‘,’0’))]”,
“endpointStatus”: “Enabled”
}
},
{
“name”: “[concat(parameters(‘webAppNamePrefix’),’-endpoint-‘,’1’)]”,
“type”: “Microsoft.Network/trafficManagerProfiles/azureEndpoints”,
“properties”: {
“targetResourceId”: “[resourceId(‘Microsoft.Web/sites/’,concat(parameters(‘webAppNamePrefix’),’-site-‘,’1’))]”,
“endpointStatus”: “Enabled”
}
}
]
}
}
],
“outputs”: {
}
}

Deploy ARM Template

Deploying Azure resource by ARM template has different ways and we will use PowerShell method. To deploy a template, typically need two steps:

  • Create a resource group. Resource group serves as the container for the deployed resources.
  • Deploy a template. The template defines the resources to create. The deployment creates the resources in the resource group specified.

Prerequisites: Need to install Azure PowerShell and connect to Azure. I am using new Azure PowerShell Az module. you can use Azurerm Powershell module to deploy.

  • Install Azure PowerShell cmdlets on your local computer.
  • Connect to Azure by using Connect-AZAccount. If you have multiple Azure subscriptions, you might also need to run Set-AzContext.
  • Download and save this template. The local file name used in this article is c:\MyTemplates\azuredeploy.json.

New-AzResourceGroupDeployment -ResourceGroupName $resourceGroupName -TemplateFile c:\MyTemplates\azuredeploy.json (modify resource group name as needed and template file location)

 

After deployment, verify your web app, traffic manager resources are available in the selected resource group.

Edit your Web App to deploy a your website:

  • In the Azure portal, under App Services, select the App service that we just deployed using the ARM template
  • Under the selected App Service, Under Development Tools Section, select App Service Editor
  • Click Go to open the editor.
  • Rename heading.html to index.html
  • Replace the content on the right side with some HTML for your website. You will see that the content is automatically saved.
  • At the top right click the preview button to see the content of your website
  • Repeat this step for other web app deployed in the second App service and change the website <body> content to reflect the geographical location
  • Again, click the preview button in the top right to verify the new content and new name

 

Testing Azure Traffic Manager

Azure Traffic Manager supports probing over both HTTPS and HTTP. For this testing, our traffic manager is configured to use HTTP.

        • In the Azure portal, select Resource Groups.
        • Then select the Traffic Manager profile name that was created using the ARM template
        • On the traffic manager profile , click Overview to see the DNS name of your newly created Traffic Manager profile. In my example, it says: http://kloudwebapp-tm-auizryiiqn3li.trafficmanager.net
        • Under Settings – > Configuration -> observe the settings for the traffic manager via the ARM template
        • Note the routing method, protocol and path.

      Testing Performance routing method

        • On your browser, enter the above traffic manager URL. We will witness the Sydney azure web site page, since we’re based in Australia and the routing method is set to performance. 
        • Now, stop the Azure web app in the Sydney location
        • On your browser, wait a few seconds and  press F5 to refresh the URL
        • Since we have routing method set to “performance” and Sydney location web app id down, we are routed to the web site hosted in Singapore

Testing weighted routing method

  • Start the Sydney web app which we stopped in the previous step
  • Now, change the traffic manager routing method to weighted
  • Change the weight priority on one endpoint (Sydney location) to 10. The weight is an integer from 1 to 1,000. The higher the weight value assigned to an endpoint, the higher its priority.
  • Since the higher weightage is allocated to Web app in Sydney, we should view Sydney page by hitting traffic manager in browser.

Testing Priority routing method

  • When you select the Priority traffic routing method, the order of the selected endpoints matters. Verify the priority order of endpoints. The primary endpoint is on top. All requests will be routed to the first endpoint and if Traffic Manager detects it to be unhealthy, the traffic automatically fails over to the next endpoint.
  • Select the Traffic Manager profile blade and verify that both the cloud services and websites that you want to include in your configuration are present.
  • In the Settings section, click Configuration -> Configuration blade -> traffic routing method settings, select the traffic routing method as Priority and click save.
  • In the Endpoints blade, review the priority order for your endpoints. Double check on the order it is displayed.
  • To change the endpoint priority order, click the endpoint, and in the Endpoint blade that is displayed, click Edit and change the Priority value as needed. Click Save to save change the endpoint settings.
  • In our example, I have set Singapore web app (#1) as priority.
  • On your browser, enter the above traffic manager URL. Singapore website should be loaded.

 

Testing Geographic routing method

  • The Geographic traffic routing method allows you to direct traffic to specific endpoints based on the geographic location where the requests originate.
  • Since endpoints of traffic manager endpoints has no geo mapping list is added and if we try to change traffic manager profile to geographic options, it will be error.
  • we need to re-create endpoints with geo-mapping list.
  • Add endpoint of app service of each geographic location with list of countries to be grouped. We select each country or select Asia or Africa or Europe.
  • Since I am working from Melbourne and on your browser, enter the above traffic manager URL. Sydney website should be loaded.
  • We could not test subnet and multi-value method, due to limitation.

I hope you found this blog useful to the understand concepts of Azure web app with Azure traffic manager and app service editor and deploying these resources using an ARM template

 

Interacting with Azure Web Apps Virtual File System using PowerShell and the Kudu API

Introduction

Azure Web Apps or App Services are quite flexible regarding deployment. You can deploy via FTP, OneDrive or Dropbox, different cloud-based source controls like VSTS, GitHub, or BitBucket, your on-premise Git, multiples IDEs including Visual Studio, Eclipse and Xcode, and using MSBuild via Web Deploy or FTP/FTPs. And this list is very likely to keep expanding.

However, there might be some scenarios where you just need to update some reference files and don’t need to build or update the whole solution. Additionally, it’s quite common that corporate firewalls restrictions leave you with only the HTTP or HTTPs ports open to interact with your Azure App Service. I had such a scenario where we had to automate the deployment of new public keys to an Azure App Service to support client certificate-based authentication. However, we were restricted by policies and firewalls.

The Kudu REST API provides a lot of handy features which support Azure App Services source code management and deployments operations, among others. One of these is the Virtual File System (VFS) API. This API is based on the VFS HTTP Adapter which wraps a VFS instance as an HTTP RESTful interface. The Kudu VFS API allows us to upload and download files, get a list of files in a directory, create directories, and delete files from the virtual file system of an Azure App Service; and we can use PowerShell to call it.

In this post I will show how to interact with the Azure App Service Virtual File Sytem (VFS) API via PowerShell.

Authenticating to the Kudu API.

To call any of the Kudu APIs, we need to authenticate by adding the corresponding Authorization header. To create the header value, we need to use the Kudu API credentials, as detailed here. Because we will be interacting with an API related to an App Service, we will be using site-level credentials (a.k.a. publishing profile credentials).

Getting the Publishing Profile Credentials from the Azure Portal

You can get the publishing profile credentials, by downloading the publishing profile from the portal, as shown in the figure below. Once downloaded, the XML document will contain the site-level credentials.

Getting the Publishing Profile Credentials via PowerShell

We can also get the site-level credentials via PowerShell. I’ve created a PowerShell function which returns the publishing credentials of an Azure App Service or a Deployment Slot, as shown below.

Bear in mind that you need to be logged in to Azure in your PowerShell session before calling these cmdlets.

Getting the Kudu REST API Authorisation header via PowerShell

Once we have the credentials, we are able to get the Authorization header value. The instructions to construct the header are described here. I’ve created another PowerShell function, which relies on the previous one, to get the header value, as follows.

Calling the App Service VFS API

Once we have the Authorization header, we are ready to call the VFS API. As shown in the documentation, the VFS API has the following operations:

  • GET /api/vfs/{path}    (Gets a file at path)
  • GET /api/vfs/{path}/    (Lists files at directory specified by path)
  • PUT /api/vfs/{path}    (Puts a file at path)
  • PUT /api/vfs/{path}/    (Creates a directory at path)
  • DELETE /api/vfs/{path}    (Delete the file at path)

So the URI to call the API would be something like:

  • GET https://{webAppName}.scm.azurewebsites.net/api/vfs/

To invoke the REST API operation via PowerShell we will use the Invoke-RestMethod cmdlet.

We have to bear in mind that when trying to overwrite or delete a file, the web server implements ETag behaviour to identify specific versions of files.

Uploading a File to an App Service

I have created the PowerShell function shown below which uploads a local file to a path in the virtual file system. To call this function you need to provide the App Service name, the Kudu credentials (username and password), the local path of your file and the kudu path. The function assumes that you want to upload the file under the wwwroot folder, but you can change it if needed.

As you can see in the script, we are adding the “If-Match”=”*” header to disable ETag version check on the server side.

Downloading a File from an App Service

Similarly, I have created a function to download a file on an App Service to the local file system via PowerShell.

Using the ZIP API

In addition to using the VFS API, we can also use the Kudu ZIP Api, which allows to upload zip files and expand them into folders, and compress server folders as zip files and download them.

  • GET /api/zip/{path}    (Zip up and download the specified folder)
  • PUT /api/zip/{path}    (Upload a zip file which gets expanded into the specified folder)

You could create your own PowerShell functions to interact with the ZIP API based on what we have previously shown.

Conclusion

As we have seen, in addition to the multiple deployment options we have for Azure App Services, we can also use the Kudu VFS API to interact with the App Service Virtual File System via HTTP. I have shared some functions for some of the provided operations. You could customise these functions or create your own based on your needs.

I hope this has been of help and feel free to add your comments or queries below. 🙂

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