Select “Deployment slots” and click “Add”. Then, enter the slot name and select the configuration source. You can create an empty slot or duplicate the production Web App by cloning the configuration from the main Web App. Once the slot is created, open this slot and notice the following URL which is a little bit different than the main. Deployment slots are live apps with their own host names. App content and configurations elements can be swapped between two deployment slots, including the production slot. Deploying your application to a non-production slot has the following benefits: You can validate app changes in a staging environment before swapping it into the production.
Azure App Service brings together everything you need to create websites, mobile backends and web APIs for any platform or device. Free and Shared (preview) plans provide different options to test your apps within your budget. Azure Storage Up to 99.99% if Read Access Geo-Replicated Storage (RA-GRS) is used App Service 99.95% Virtual Machine 99.95% (when two instances are deployed).
Azure Sitecore Deployment: Deploying to a Slot
August 10, 2017 | Charlie Turano
This is part 5 in our series of blog posts on Sitecore deployments on Azure. The other posts in this series can be found here:
1. Setting Up the Solution and VSO Build
2. Preparing the Default Scripts and Packages for Azure Deployment
3. Adding Custom Modules to an Azure Deployment
4. Adding Project's Code and Items to the Azure Deployment
In the previous post, we completed our Sitecore Azure setup, including a custom module and our initial project.
At this point, we want to setup Azure staging slots, so the next release of our project can go there. This allows us to deploy the new code to a private website (the slot), and test it before pushing it live for the public to see. We are going to script this, to make this really easy for the devops team to automate. The following tasks need to be performed:
Create a 'databaseless' cd package.
Configure the deployment parameters for the slot
Setup a powershell script to run the deployment
Create and Upload the Databaseless Package
The Sitecore 8.2 rev. 170407_cd-nodb.scwdp.zip was obtained by following the directions on Rob Habraken's excellent blog post Blue Green Sitecore Deployments on Azure. Please see the section toward the bottom entitled Databaseless SCWDPs, and use this script to generate a Databaseless SCWDP of the CD package.
- Extract the parameters.xml out of the default CD package.
- Open a PowerShell prompt, and run the script with the following
Upload this package to your blob storage.
Configuring the deployment parameters
Azure Deployment Slots Pricing Chart
Using the file azuredeploy.parameters_slot.json.example as a starting point, create a azuredeploy.parameters_slot.json file, which will make configuring the deployment much easier. Most of the settings should be the same as the settings in the azuredeploy.parameters.json file. The notable differences are the paths to the modules (the '_cdslot' variations) and the additional settings for the web and master database servers. The package referenced in the CD package will reference the databaseless package we just created and uploaded.
The azuredeploy.parameters_slot.json should be updated to point at a new MSDeploy package for the instance of Launch Sitecore you are deploying. This will push a new version of the code.
As with the earlier posts, take the _cdslot configuration files for the bootloader, SitecorePackageDeployer and the InstallMSDeployPackage and upload them into your Blob Storage.
You then need to get the public URLs for these files, and add them into your azuredeploy.parameters_slot.json file, mentioned above.
The CD Slot Arm Template
Now upload the main azuredeploy slot template to your blob storage (remember to keep the same relative path to the other arm template files as it is in our Github repo).
The Powershell scripts
The powershell script to install the deployment slot is very similar to the script used to install the original instance, instead it uses the azuredeploy_cdslot template instead. The example script is called ProvisionAndDeploySlot.ps1.example. You should update the parameters to point to your Sitecore installation and execute the powershell script. This will install a slot called 'cd_staging' in your azure web instance, along with the new version of the LaunchSitecore site (remember, you updated the package path to the new MSDeploy package).
Once run, this entire Staging slot is provisioned with a clean version of the code from the new release. It is currently using the same databases as production though (more on that in the next post), but it is kept private, allowing us to test the new code out to see how our site looks, before affecting any of our public users.
Swapping live for Staging
Once the staging instance has tested and we are ready to push live, the instance can be easily swapped out with the one in production. Select the cd server in the Azure dashboard and click on the Swap button:
Viewing the website, we can see that the new release of our code has been deployed to the production website. Because we had it running in the staging slot earlier, it has already been warmed up and there is no downtime to our front-end users.
Catching up? Start at the beginning! Check out Part 1 of our series, or read the complete project on Github.
Azure App Services is extremely useful for developers. It offers Web Apps, API Apps, Mobile Apps and Function Apps (that run Azure Functions). All of these apps are incredibly powerful and can literally get you up and running in minutes. They provide a host of amazing features that you can leverage, like (auto)scaling, easy authentication, offline sync (for Mobile Apps), hybrid connections and many, many more. One feature that all of these apps share, is probably the most underrated one that many people don’t know about: deployment slots.
What Are Deployment Slots?
Deployment slots are incredible! They are the reason for many people to start using Azure App Services, like Web Apps. Let me explain why:
Suppose that you have a Web App. You run your website in it and it has an URL like production.website.com. In Azure App Services, you can very easily add a deployment slot. This is actually a full-fledged App Service, in this case a Web App, that sits next to you original Web App. The deployment slot has a different URL, maybe something like staging.website.com. Users use your website that is in the original Web App, because that is your production environment. You can deploy a new version of the website in the deployment slot, just so that you can test it before it goes live.
You could also do that in another Web App. But here is the magic of deployment slots: You can now Swap the deployment slot with production. When you do this, users will notice almost nothing and experience no downtime. The swap functionality of the deployment slot takes care of this magic. Isn’t that awesome?
Deployment Slot Facts
Before I tell you even more things that make deployment slots awesome, let me state out the facts about deployment slots:
- A deployment slot is a full-fledged App Service that lives within the same App Service Plan as your original App Service
- This means that deployment slots use some of the resources in the App Service Plan, which could influence the performance of your main App Service
- The original App Service is also called the production slot
- Deployment slots can copy the configuration (AppSettings and Connectionstrings) of the original App Service or other deployment slots
- Your App Service needs to (at least) be in the Standard Pricing tier
- You can create 4 deployment slots next to your original App Service in the Standard Pricing tier
- And you can create 19 deployment slots next to your original App Service in the Premium Pricing tier
- When you scale a deployment slot (up or out), you also scale all the other slots of the App Service. This is because all slots share the same App Service Plan
- If you have installed any site extensions, you need to do that again in a deployment slot as it is a new App Service instance
- Deployment slots have a different URL then the original App Service. This URL is based on the name you give the deployment slot, for instance “staging” can become http://website-staging.azurewebsites.net
Alright, let’s take a look at how to setup deployment slots and what the major benefits are in more detail.
Setting up Deployment Slots
Creating a deployment slot is very easy and, as always, there are many ways to do it. You can use the Azure Portal, Azure CLI, Azure PowerShell and the Azure Management API. I’ll show you how to do it using the Azure Portal.
In the Azure Portal, navigate to your App Service - let’s say it’s a Web App - and click the deployment slots menu item:
Now you see the Add Slot button, which opens the Add Slot dialog, to the right of the screen. Here, you need to enter a name, and choose if you want to copy the configuration from another slot, or not at all. Click OK and voila, you have a deployment slot!
Choosing to copy the configuration is important, because your app probably does things like connect to a database or cache and has specific connectionstrings in these settings.
Visit my Pluralsight course for a full video tutorial about setting up and using deployment slots.
Deploying your app to deployment slots
When you have created a deployment slot, it is empty, just like when you create a new App Service. You need to deploy a version of your app to the deployment slot before you can use it.
You can use the same tools and techniques that you use to deploy your app to the App Service: through Visual Studio, using something like VSTS (Visual Studio Team Services) or Octopus Deploy, using Web Deploy or any number of other technologies. Selecting a deployment slot to deploy to from Visual Studio looks like this:
Swap and Rollback
One of the major benefits of deployment slots is that you can swap them. What does that mean?
Suppose that I have a website deployed in a Web App. This Web App has the custom URL https://www.azure-overview.com/. I have created a new version of the website and want to test it before publishing it. So I create a deployment slot called staging, which has the URL http://azureoverview-staging.azurewebsites.net. I’ve made sure that the slot has the same configuration values so that I use the same database and cache as production does. I’ve deployed the new website in the deployment slot and I’m happy with my changes and want to deploy to production. I can do this by performing a swap:
I can do this from the Azure Portal, Azure CLI, Azure PowerShell and the Azure Management API. In the Azure Portal, I can choose what the source and destination slots are and click OK. This will swap the slots and will deploy my changes to production. Here’s the thing: Users will experience no downtime!
And that’s because a swap does the following:
- The source slot will be warmed-up. Azure does this by firing a couple requests into the root of the slot. You can also configure custom warm-up rules
- Swaps the Virtual IP addresses of the source and destination slots, thereby swapping the URLs of the slots
- It also applies (or keeps, depending on how you see it) certain settings that are specific to the target slot:
- Publishing endpoints
- Custom Domain Names
- SSL certificates and bindings
- Scale settings
- WebJobs schedulers
This results in a seamless transition to production. Users experience virtually no downtime. I say virtually because users that are in the midst of doing something that depends on state that is in-memory of the Web App, will lose this state. But you shouldn’t keep state locally in an App Service anyways in Azure as you should assume that everything in Azure is volatile.
After a swap, the “old” website will be in the staging slot and the “new” website in the production slot.
If you aren’t happy with the version in production, you can easily rollback your deployment. Simply swap back to reverse the effect!
You can swap manually, but you have more options:
You can choose to swap automatically to a slot when there is a new version of your app in a deployment slot – this is called Auto Swap. Simply enable it in the Application Settings of the deployment slot:
Swap with preview
You can choose to swap with preview when you perform a swap from the Azure Portal. This does the following:
- It performs the swap in stages
- It applies the configuration elements of the destination slot to the source slot, so that you can test if everything works as expected, before the actual swap happens
- (if you complete the swap), it does the same as in a manual swap, warm-up the slot and perform the swap
Swap and VSTS
If you use something like VSTS (Visual Studio Team Services), you can also leverage deployment slots and the swap feature. You can deploy a new version of your app to a deployment slot and then swap it using steps in a release definition. The illustration below shows this for a release definition in VSTS:
Testing in Production
Besides swapping, deployment slots offer another killer feature: testing in production. Just like the name suggests, using this, you can actually test in production. This means that you can route a specific percentage of user traffic to one or more of your deployment slots:
With testing in production, you can have some users use the new version of your application. This way, you can see if and how they use new features. In order to find this out, you need to make sure that you monitor everything, with something like Stackify Retrace.
Testing in production is easy to setup. In the Azure Portal, choose the testing in production menu option in your App Service.
Here, you can choose the deployment slots that you want to route traffic to (or add new ones) and assign a percentage of traffic to them. That’s it! Now users will be routed to your deployment slots – super powerful!
Deployment slots are awesome and I hope that you give them a chance. You can use them for all sorts of things, but there are also things to keep in mind. Here is the quick overview:
- Using the **swap **feature gives you zero-downtime deployments
- You can test the new version of your app using the testing in production feature
- Deployment slots are great to verify a new version of an app before it goes live
Azure Deployment Slots Pricing Guide
- A deployment slot is a full-fledged App Service that lives within the same App Service Plan as your original App Service, which might impact the performance of your original App Service
- A deployment slot is a new App Service. This means that you have to reinstall any site extensions that you have installed in you App Service
- Your App Service needs to (at least) be in the Standard Pricing tier
- You can’t scale a deployment slot, separate from other deployment slots in the App Service. This makes a deployment slot not suitable for performance testing – you should use a separate App Service for that
Azure Deployment Slots Pricing
Start using deployment slots and use them wisely! Let me know what you think in the comments.