Summary
In this module, you defined a deployment pattern as an automated way to smoothly roll out new application features to your users. A good deployment pattern can help you minimize downtime. It can also enable you to roll out new features progressively to your users.
You can choose from several deployment patterns. The deployment pattern you choose depends on your reasons for the deployment and your resources. Do you have canary testers in place? Will you employ a dark launch and choose testers who don't know that they're testers? If you have a trusted set of testers that progressively increases from a small set to a larger set, then you could choose a progressive-exposure deployment. Or, if you want to know if one version performs better than another version, you could choose A/B testing.
The Tailspin team chose to implement the blue-green deployment pattern, using deployment slots in Azure App Service. Deployment slots are live apps that have their own host names. The team can swap two deployment slots. By swapping, they can promote changes to production instantly. Although the team isn't ready to release their website to the public, they've proven that they can get new features to their users without incurring downtime.
As a bonus, in this module you also learned how to roll forward an unintended change by reverting a Git commit and then pushing the reverted change through the pipeline.
How is the team measuring up?
In the Assess your existing software development process module, Mara did a value-stream mapping exercise. The exercise helped the team analyze their current release-cycle process.
Recall that the activity ratio, or efficiency, is process time divided by total lead time:
$${Activity\ ratio\ =\ }{\dfrac{Process\ time}{Total\ lead\ time}}$$
The Tailspin web team initially used this metric to determine that they were 23 percent efficient.
The team first reduced some inefficiencies when they implemented continuous integration (CI). By applying continuous delivery (CD), they have now reduced inefficiencies even further.
In previous learning paths, the team reduced:
The time it takes to set up source control for new features. The required time went from three days to zero days.
The team achieved this improvement by moving from centralized source control to Git, a form of distributed source control. By using distributed source control, they don't need to wait for files to be unlocked.
The time it takes to deliver code to Amita, the tester. The required time went from two days to zero days.
The team achieved this improvement by moving their build process to Azure Pipelines. Azure Pipelines automatically notifies Amita when a build is available. Developers no longer need to update Amita's spreadsheet to notify her.
The time it takes Amita to test new features. The required time went from three days to one day.
The team achieved this improvement by unit-testing their code. They run unit tests each time a change moves through the build pipeline, so fewer bugs and regressions reach Amita. The reduced workload means that Amita can complete each manual test faster.
The release pipeline that you and the team built in this learning path reduced:
The time it takes to get the build into the Test stage. The required time went from three days to one day.
The team achieved this by using a scheduled trigger to deploy to Test every day at 3:00 AM.
The time it takes to get the tested build into Staging. The required time went from two days to zero days.
The team achieved this improvement by adding Selenium UI tests, a form of functional testing, to the Test stage. These automated tests are much faster than the manual versions.
The time it takes to get the approved build from Staging to live. The required time went from one day to less than one day.
The team achieved this improvement by adding manual approval checks to the pipeline. When management signs off, Tim can release the changes from Staging to live.
These changes reduce the total lead time from 22 days to 10 days. When we substitute these numbers into the equation:
$${Activity\ ratio\ =\ }{\dfrac{5\ days}{10\ days}}{ = 0.50}$$
Multiply the result by 100 percent, and we get a 50 percent reduction.
Although there's always room for improvement, this change is a win for the team. Not only do customers get value more quickly, the Tailspin team now spends less time waiting and more time doing what they enjoy most: delivering features that they know their customers will love.
Learn more
Use these additional resources to learn more about App Service, deployment slots, and rolling back changes: