Continuous Integration vs. Continuous Delivery vs.

Question

What's the difference between these three terms? My university provides the following definitions:

Continuous Integration basically just means that the developer's working copies are synchronized with a shared mainline several times a day.

Continuous Delivery is described as the logical evolution of continuous integration: Always be able to put a product into production!

Continuous Deployment is described as the logical next step after continuous delivery: Automatically deploy the product into production whenever it passes QA!

They also provide a warning: Sometimes the term "Continuous Deployment" is also used if you are able to continuously deploy to the test system.

All this leaves me confused. Any explaination that is a little more detailed (or comes with an example) is appreciated!

Answer 1

Continuous Integration basically just means that the developer's working copies are synchronized with a shared mainline several times a day.

Or more than several times per day. As often as any given discrete task is completed, basically. Consider for example a team of developers working on a single business application. In many environments, the following may happen:

• One or two developers keep local changes for a few days because "it's not ready yet".
• One or two developers create branches in the source control so they can work on their feature(s) "without being bothered by other people's changes".

These can lead to problems. Poor code/task organization leads to branching, branching leads to merging, merging... leads to suffering. Continuous integration as a practice addresses this by encouraging everybody to work from the same shared source. Individual work items should be discrete enough to be completed in a short amount of time (hours at most).

Basically the general idea is that integrating a small change in a small amount of work. Integrating a large change is a disproportionately large amount of work. The aggregate of integration work is smaller if done in constant small steps. This allows developers to spend more time working on business-visible features instead of development process overhead.

Continuous Delivery is described as the logical evolution of continuous integration: Always be able to put a product into production!

This follows the same idea of discrete, well defined work items. If there's a single master codebase which is only ever adjusted in small increments by complete, tested, known working features then that codebase is always stable. Automated testing is key here to be able to prove that stability at the push of a button.

The less stabilization work that needs to be done (which, again, is development process overhead and should be eliminated), the more often that codebase can be pushed to any given environment. In a lot of companies a deployment can be a pretty grueling process. Even a week-long all-hands-on-deck operation. This is expensive and produces no business value. By employing good work item definitions, effective automated testing, and continuous integration a team can be in a position to automate the codebase's delivery to any given environment.

Continuous Deployment is described as the logical next step after continuous delivery: Automatically deploy the product into production whenever it passes QA!

You'll rarely see this happen in a business environment, and it's quite a joy when it's encountered. If the codebase can be automatically tested and automatically deployed to any given environment then, well, production is an environment like any other. So if the team has built up to this point then there's a potential for significant value to the business by always being able to deploy updates to production.

Defect fixes are sent to customers faster, new features reach the market faster, new ideas are tested against the market in smaller increments to allow for redirection of priorities, etc.

For example, let's say a company has a big idea for a new feature in their software-based product or service. They've done some research, they know the market, and they believe this idea will result in a strong new line of revenue. Now consider two options for delivering that feature:

1. Spend months developing the whole thing in a one-off branch. Spend weeks integrating it back into the main codebase. Spend days testing it. Spend a day deploying it. And only then start tracking actual revenue in the production system.
2. Implement small parts of the feature, one at a time. Each week release a new piece of it. Each week get more data on actual revenue.

In the first scenario, if the feature doesn't have the desired market effect then a lot of money is wasted on something customers don't actually want. In the second scenario the fact that customers don't want it is determined much, much earlier and the rest of the work is de-prioritized.

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Ultimately these "continuous things" are all about removing development process overhead. If a company's line of revenue is a particular service offering then ideally all of their costs should go into that offering. Development process overhead (merging code, re-testing the same features after a merge, manual deployment tasks, etc.) don't actually contribute to the value of the service, so these concepts seek to remove those costs from the process.

Answer 2

Atlassian posted a good explanation about Continuous integration vs. continuous delivery vs. continuous deployment.

In a nutshell:

Continuous Integration - is an automation to build and test application whenever new commits are pushed into the branch.

Continuous Delivery - is Continuous Integration + Deploy application to production by "clicking on a button" (Release to customers is often, but on demand).

Continuous Deployment - is Continuous Delivery but without human intervention (Release to customers is on-going).

Answer 3

DevOps is a combination of 3C's - continuous, communication, collaboration and this lead to prime focus in various industries.

In an IoT connected devices world, multiple scrum features like product owner, web, mobile and QA working in an agile manner in a scrum of scrum cycle to deliver a product to end customer.

Continuous integration: Multiple scrum feature working simultanrouly in multiple endpoints

Continuous delivery: With integration and deployment, delivery of product to multiple customers to be handled at the same time.

Continuous deployment: multiple products deployed to multiple customers at multiple platform.

Watch this to know how DevOps enabling IoT connected world: https://youtu.be/nAfZt2t4HqA

Answer 4

I think we're over analyzing and maybe complicating a bit the "continuous" suite of words. In this context continuous means automation. For the other words attached to "continuous" use the English language as your translation guide and please don't try to complicate things! In "continuous build" we automatically build (write/compile/link/etc) our application into something that's executable for a specific platform/container/runtime/etc. "Continuous integration" means that your new functionality tests and performs as intended when interacting with another entity. Obviously, before integration takes place, the build must happen and thorough testing would also be used to validate the integration. So, in "continuous integration" one uses automation to add value to an existing bucket of functionality in a way that doesn't negatively disrupt the existing functionality but rather integrates nicely with it, adding a perceived value to the whole. Integration implies, by its mere English definition, that things jive harmoniously so in code-talk my add compiles, links, tests and runs perfectly within the whole. You wouldn't call something integrated if it failed the end product, would you?! In our context "Continuous deployment" is synonymous with "continuos delivery" since at the end of the day we've provided functionality to our customers. However, by over analyzing this, I could argue that deploy is a subset of delivery because deploying something doesn't necessarily mean that we delivered. We deployed the code but because we haven't effectively communicated to our stakeholders, we failed to deliver from a business perspective! We deployed the troops but we haven't delivered the promised water and food to the nearby town. What if I were to add the "continuous transition" term, would it have its own merit? After all, maybe it's better suited to describe the movement of code through environments since it has the connotation of "from/to" more so than deployment or delivery which could imply one location only, in perpetuity! This is what we get if we don't apply common sense.

In conclusion, this is simple stuff to describe (doing it is a bit more ...complicated!), just use common sense, the English language and you'll be fine.