Welcome!

Blog Feed Post

Why Azure deployment slots are awesome and how to use them

Azure App Services is extremely useful for developers. It offers Web Apps, API Apps, Mobile Apps and Function Apps (that run Azure Functions). 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 much, much more. One feature that 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:

azure-slots-diagram

Suppose that you have a Web App deployed in an Azure App Service and it has a URL like production.website.com. In Azure App Services, you can very easily add an additional deployment slot. This is a full-fledged App Service, in this case, another Web App, that sits next to you original Web App. The deployment slot has a different URL, maybe something like staging.website.com. Your users would be accessing your original Web App because that is your production environment slot. You can deploy a new version of the Web App into a secondary deployment slot, so you can test it before it goes live.

Instead of deploying your Web App to a staging slot, you could have deployed it as whole new App Service. But here is the magic of deployment slots: You can now Swap the staging deployment slot with production within your same App Service. 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:

  • Each deployment slot is like a full-fledged App Service instance
  • The original App Service deployment slot is also called the production slot
  • Deployment slots can copy the configuration (AppSettings and Connectionstrings) of the original App Service or other deployment slots
  • 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
  • Because all deployments lots run within the same App Service and it’s App Service Plan, deployment slots are free to use if you are using the Standard pricing tier or higher
  • 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 than 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 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:

Creating Azure deployment slots

Creating an Azure deployment slot

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:

Deploy to azure deployment slot

 

Swap and Rollback

One of the major benefits of deployment slots is that you can swap them. What does that mean?

Swapping

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:

Swapping an Azure Deployment Slot

Swapping an Azure Deployment Slot

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
  • Azure 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
    • Site extensions

This results in a seamless transition to production. Users experience virtually no downtime. I say virtually because users that are amid 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.

Rollback

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!

Swapping options

You can swap deployment slots manually, but you have more options that you should consider.

Auto Swap

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:

Deployment slot settings

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 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
Swapping an Azure Deployment Slot with preview

Swapping an Azure Deployment Slot with preview

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:

azure slot 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:

slot percentage traffic

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 for Azure monitoring.

Setup

Testing in production is easy to setup. In the Azure Portal, choose the testing in production menu option in your App Service.

Door computer gegenereerde alternatieve tekst: Search (Ctrl +1) App Service Editor (P reviev•) Performance test Resource explorer pep Debugging Testing in production Extensions Save X Disca rd Static Routing O Choose deployment slot Add Slot TRAFFIC Traffic %

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!

Conclusion

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:

Pros:

  • 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
  • Deployment slots are free!

Cons:

  • A deployment slot is a new App Service. This means that you must reinstall any site extensions that you have installed in your 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

Start using deployment slots and use them wisely! Let me know what you think in the comments!

The post Why Azure deployment slots are awesome and how to use them appeared first on Stackify.

Read the original blog entry...

More Stories By Stackify Blog

Stackify offers the only developers-friendly solution that fully integrates error and log management with application performance monitoring and management. Allowing you to easily isolate issues, identify what needs to be fixed quicker and focus your efforts – Support less, Code more. Stackify provides software developers, operations and support managers with an innovative cloud based solution that gives them DevOps insight and allows them to monitor, detect and resolve application issues before they affect the business to ensure a better end user experience. Start your free trial now stackify.com

Latest Stories
SYS-CON Events announced today that Linux Academy, the foremost online Linux and cloud training platform and community, will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Linux Academy was founded on the belief that providing high-quality, in-depth training should be available at an affordable price. Industry leaders in quality training, provided services, and student certification passes, its goal is to c...
DevOps is often described as a combination of technology and culture. Without both, DevOps isn't complete. However, applying the culture to outdated technology is a recipe for disaster; as response times grow and connections between teams are delayed by technology, the culture will die. A Nutanix Enterprise Cloud has many benefits that provide the needed base for a true DevOps paradigm. In his Day 3 Keynote at 20th Cloud Expo, Chris Brown, a Solutions Marketing Manager at Nutanix, will explore t...
Providing the needed data for application development and testing is a huge headache for most organizations. The problems are often the same across companies - speed, quality, cost, and control. Provisioning data can take days or weeks, every time a refresh is required. Using dummy data leads to quality problems. Creating physical copies of large data sets and sending them to distributed teams of developers eats up expensive storage and bandwidth resources. And, all of these copies proliferating...
SYS-CON Events announced today that SoftLayer, an IBM Company, has been named “Gold Sponsor” of SYS-CON's 18th Cloud Expo, which will take place on June 7-9, 2016, at the Javits Center in New York, New York. SoftLayer, an IBM Company, provides cloud infrastructure as a service from a growing number of data centers and network points of presence around the world. SoftLayer’s customers range from Web startups to global enterprises.
SYS-CON Events announced today that StorageCraft Technology Corp, a global leader in backup and disaster, will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. The StorageCraft family of companies, founded in 2003, provides award-winning backup, disaster recovery, system migration and data protection solutions for servers, desktops and laptops in addition to powerful data analytics.
In his session at @ThingsExpo, Eric Lachapelle, CEO of the Professional Evaluation and Certification Board (PECB), will provide an overview of various initiatives to certifiy the security of connected devices and future trends in ensuring public trust of IoT. Eric Lachapelle is the Chief Executive Officer of the Professional Evaluation and Certification Board (PECB), an international certification body. His role is to help companies and individuals to achieve professional, accredited and worldw...
SYS-CON Events announced today that Auditwerx will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Auditwerx specializes in SOC 1, SOC 2, and SOC 3 attestation services throughout the U.S. and Canada. As a division of Carr, Riggs & Ingram (CRI), one of the top 20 largest CPA firms nationally, you can expect the resources, skills, and experience of a much larger firm combined with the accessibility and attent...
SYS-CON Events announced today that Technologic Systems Inc., an embedded systems solutions company, will exhibit at SYS-CON's @ThingsExpo, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Technologic Systems is an embedded systems company with headquarters in Fountain Hills, Arizona. They have been in business for 32 years, helping more than 8,000 OEM customers and building over a hundred COTS products that have never been discontinued. Technologic Systems’ pr...
SYS-CON Events announced today that CA Technologies has been named “Platinum Sponsor” of SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY, and the 21st International Cloud Expo®, which will take place October 31-November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. CA Technologies helps customers succeed in a future where every business – from apparel to energy – is being rewritten by software. From ...
With major technology companies and startups seriously embracing Cloud strategies, now is the perfect time to attend @CloudExpo | @ThingsExpo, June 6-8, 2017, at the Javits Center in New York City, NY and October 31 - November 2, 2017, Santa Clara Convention Center, CA. Learn what is going on, contribute to the discussions, and ensure that your enterprise is on the right path to Digital Transformation.
HyperConvergence came to market with the objective of being simple, flexible and to help drive down operating expenses. It reduced the footprint by bundling the compute/storage/network into one box. This brought a new set of challenges as the HyperConverged vendors are very focused on their own proprietary building blocks. If you want to scale in a certain way, let’s say you identified a need for more storage and want to add a device that is not sold by the HyperConverged vendor, forget about it...
FinTech is the sum of financial and technology, and it’s one of the fastest growing tech industries. Total global investments in FinTech almost reached $50 billion last year, but there is still a great deal of confusion over what it is and what it means – especially as it applies to retirement. Building financial startups is not simple, but with the right team, technology and an innovative approach it can be an extremely interesting domain to disrupt. FinTech heralds a financial revolution that...
What if you could build a web application that could support true web-scale traffic without having to ever provision or manage a single server? Sounds magical, and it is! In his session at 20th Cloud Expo, Chris Munns, Senior Developer Advocate for Serverless Applications at Amazon Web Services, will show how to build a serverless website that scales automatically using services like AWS Lambda, Amazon API Gateway, and Amazon S3. We will review several frameworks that can help you build serverle...
Most companies are adopting or evaluating container technology - Docker in particular - to speed up application deployment, drive down cost, ease management and make application delivery more flexible overall. As with most new architectures, this dream takes a lot of work to become a reality. Even when you do get your application componentized enough and packaged properly, there are still challenges for DevOps teams to making the shift to continuous delivery and achieving that reduction in cost ...
SYS-CON Events announced today that Loom Systems will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Founded in 2015, Loom Systems delivers an advanced AI solution to predict and prevent problems in the digital business. Loom stands alone in the industry as an AI analysis platform requiring no prior math knowledge from operators, leveraging the existing staff to succeed in the digital era. With offices in S...