CircleCI 2.0 is a completely updated CI/CD platform that starts every run with a clean image which is automatically provisioned just-in-time for Linux and Android jobs on the hosted CircleCI application.
Configuration moves into the code in 2.0, so every developer can configure jobs directly in their working branch, teams can try new things without the risk of slowing anyone else down, and business leaders have the ability to operate large global teams with minimal overhead. CircleCI 2.0 prevents you from writing clean-up scripts because every run starts in the same state, eliminating the risk of polluting a test database or leaving files in places that cause problems for the next run.
The CircleCI 2.0 platform includes significant performance, stability, and reliability improvements along with the following new features:
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First-class Docker Support: Choose any image to run your job steps, customizable on a per-job basis on a particular Git branch. Speed up your run times with advanced layer caching. Build docker images with full docker CLI support and full support for docker compose. Support for all programming languages and custom environments that offer more predictable output. See Specifying Container Images for instructions.
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Workflows: Orchestrate jobs and steps with great flexibility using a simple set of new keys in your configuration. Share temporary files between jobs with workspaces for fan-in, fan-out, parallel, and sequential runs. Hold a workflow for a manual approval and restart a workflow from a failed job. See Orchestrating Workflows for details.
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Resource Allocation: Configure your CPU and RAM needs on a per-job basis at the branch level, see the resource_class documentation for instructions. Paid accounts may request this feature from their Customer Success Manager, non-paid users may request to get started by sending email to support@circleci.com.
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Insights: Access interactive charts and analyses in seconds. Visualize trends in your build history to identify and pinpoint bottlenecks. Understand all of your builds at a glance. View the builds that fail most, so you can fix the slowest tests to improve efficiency. See the Collecting Test Metadata documentation for information.
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Debugging with SSH and CLI: Perform local job runs, configuration validation and SSH in to builds for access to log files and debugging running processes. See Using the CLI documentation to learn about running local jobs and refer to Debugging Jobs over SSH for SSH instructions.
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Parallelism: Automatic provisioning of containers as they are freed without waiting for other jobs to finish. See the Parallel Job Execution documentation for examples.
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Advanced Caching: Speed up builds by caching files from run to run using keys that are easy to control with granular caching options for cache save and restore points throughout your jobs. Cache any files from run to run using keys you can control, see the Caching Dependencies documentation for strategies and steps.
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Demonstration Applications: See the Language Guides and Demo Repos to learn CircleCI configuration by example for applications written in Go, Javascript, PHP, Python (Django and Flask), Ruby on Rails, Java, Elixir, and Clojure.
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New Documentation: New and restructured documentation including an Overview, Hello World, Sample 2.0 config.yml File, simplified instructions for Migrating from 1.0 to 2.0, plus examples for Configuring Databases and Creating Custom Docker Images. Refer to the Migration FAQ for common questions and known limitations.