CircleCI vs Concourse CI

CircleCI excels with its setup process. All that's needed is a GitHub login and CircleCI automatically detects the settings for Ruby, Python, Node.js, Java and Clojure. The setup process is their most widely praised feature.

CircleCI can be connected to any project that is hosted on GitHub by logging in using the GitHub OAuth and adding the desired repository.

Whenever a new commit is pushed to GitHub, CircleCI runs the tests that have been already defined and if none of them fails, the build is deployed to the runtime environment.

Users can access the Virtual Machine via SSH and run commands.

In most cases CircleCI automatically get settings from your code. When it fails, edit circle.yml.

Tests can be parallelized across multiple machines reducing test times drastically. They support up to 8-way parallelization. Additionally, CircleCI caches the build environment.

Circle CI's web UI is clean and easy to use.

It gives all the information for a single build in a feed and gives the explanation for each step of the build, what it's doing and what the step is related to. On the top it displays author information and the time and date when the build was started and finished.

This is all done by giving only the most essential information without clogging the screen.

Support for Ruby, Python, Node, Java, PHP, RoR, DJ, JavaScript. It also detects settings for Ruby, Python, Node.js, Java and Clojure.

It als has support for: MySQL, MongoDB, PostgreSQL, Cassandra, Riak, Redis, SQLite, Solr, CouchDB, ElasticSearch, Neo4j, Couchbase, Lucene, Sphinx, ThriftDB, Memcache.

Alongside latest Chrome, Firefox and Webkit (installed using xvfb), CircleCi supports the use of Selenium, PhantomJS as well as tools like Capybara and Cucumber.

Support for RabbitMQ, Beanstalk and Resque through Redis.

CircleCI can continuously deliver Docker images to hosts that support Docker containers.

Eg:
./1.setup.sh 48s
./2.build.sh 56s
With this information, it's easy to find out which line of the script is the bottleneck of the build process.

Can specify the cache dependencies on

1. checksum "package.json"
2. Branch
3. BuildNum
4. Revision
5. Environment.variableName

For more details https://circleci.com/docs/2.0/caching/

CircleCI can notify via email, Hipchat, Campfire and more. And it does so only when necessary.

You can push multiple batches of code concurrently.

Support for Heroku, AWS, Engine Yard, dotCloud, Fabric, Nodejitsu, AppFog, Capistrano, Rockspace, Joynet.

Integration with Heroku is solid with the ability to automatically deploy or merge branches.

CircleCI is also very flexible with the deployment arrangement allowing SSH key management, deployment freedom including directly to a PaaS, using Capistrano, Fabric, arbitrary bash commands, or by auto-merging to another branch, or packaging code up to S3.

Debugging on remote build agents is a nightmare (especially without isolated builds). Concourse CI can be run locally. When there are problems with the pipeline definition, it can be run and debugged locally. That means it takes less time to find and fix problems.

Resources are to Concourse as plugins are to Jenkins. In other words, resources allow Concourse CI to do just about any work necessary in a build. But resources follow a "service provider interface" that makes them easy to build in any language (not just JVM languages) and have a clearly defined computing model, built for composition. Resources don't clutter UI or tax performance.

BOSH is an open source tool for release engineering, deployment, lifecycle management, and monitoring of distributed systems. Since Concourse CI is built on top of BOSH, Concourse can scale across many servers or be run in the Cloud.

Build isolation keeps workers "clean". There's no configuration drift of agents. Or flaky interactions between build jobs.

Visual pipeline view makes it clear what the automation does. Simple navigation to logs makes it easy to understand what happened in a build.

Concourse defines three primitives that, together, can express arbitrary features and pipelines.