Canary release strategy vs. Blue/Green

I have written a detailed essay on this topic here: http://blog.itaysk.com/2017/11/20/deployment-strategies-defined

In my opinion, the difference is whether or not the new 'green' version is exposed to real users. If it is, then I'd call it Canary. A common way to implement Canary is regular Blue/Green with the addition of smart routing of specific users to the new version. Read the post for a detailed comparison

Blue/Green:

Canary:

Blue-green releasing is simpler and faster.

You can do a blue-green release if you've tested the new version in a testing environment and are very certain that the new version will function correctly in production. Always using feature toggles is a good way to increase your confidence in a new version, since the new version functions exactly like the old until someone flips a feature toggle. Breaking your application into small, independently releaseable services is another, since there is less to test and less that can break.

You need to do a canary release if you're not completely certain that the new version will function correctly in production. Even if you are a thorough tester, the Internet is a large and complex place and is always coming up with unexpected challenges. Even if you use feature toggles, one might be implemented incorrectly.

Deployment automation takes effort, so most organizations will plan to use one strategy or the other every time.

So do blue-green deployment if you're committed to practices that allow you to be confident in doing so. Otherwise, send out the canary.

The essence of blue-green is deploying all at once and the essence of canary deployment is deploying incrementally, so given a single pool of users I can't think of a process that I would describe as doing both at the same time. If you had multiple independent pools of users, e.g. using different regional data centers, you could do blue-green within each data center and canary across data centers. Although if you didn't need canary deployment within a data center, you probably wouldn't need it across data centers.

Although both of these terms look quite close to each other, they have subtle differences. One put confidence in your functionality release and the other put confidence the way you release.

Canary

1. The canary release is a technique to reduce the risk of introducing a new software version in production by slowly rolling out the change to a small subset of users before rolling it out to the entire infrastructure.

2. It is about to get an idea of how new version will perform (integrate with other apps, CPU, memory, disk usage, etc).

Blue/Green:

1. It is more about the predictable release with zero downtime deployment.
2. Easy rollbacks in case of failure.
3. Completely automated deployment process

Here are some inline definition -

• Blue-Green Deployment - When deploying a new version of an application, a second environment is created. Once the new environment is tested, it takes over from the old version. The old environment can then be turned off.

   

• A/B Testing - Two versions of an application are running at the same time. A portion of requests go to each. Developers can then compare the versions.  
• Canary Release - A new version of a microservice is started along with the old versions. That new version can then take a portion of the requests and the team can test how this new version interacts with the overall system.