Concepts

Semaphore manages your build, test and deployment workflows with pipelines, blocks, and promotions. Workflows may contain multiple pipelines, for example one for tests and another for deployment. Blocks define what to do at each step in the pipeline. Promotions connect different pipelines. Semaphore schedules and runs the blocks on agents. Each agent manages the environment the blocks run in. All configuration is written in YAML files. The initial pipeline is always kept in .semaphore/semaphore.yml. Promoted pipelines have different filenames.

Semaphore 2.0 concepts diagram

Blocks & Tasks

Blocks are the heart of a pipeline. Each block has a task that defines one or more jobs. Jobs define the commands to execute.

If your task contains multiple jobs, they are executed in parallel. So, a "test" task could define jobs for "linting", "unit tests", and "integration tests" that run in parallel, making the task finish faster.

Blocks are executed sequentially, waiting for all tasks in the previous block to complete before continuing. Each task can configure its own environment, including machine type, set its own environment variables and use any predefined secret.

We will see how to define blocks, tasks and jobs later in this guide. You can also refer to the pipeline reference docs for complete information.

Promotions

Promotions are junctions blocks in your larger workflow. Promotions are commonly used for deployment and promoting builds to different environments. A pipeline can have multiple promotions. Promoting loads an entirely new pipeline, so you can build up complex pipelines using only configuration files.

We will see how we can manage deployment using promotions later in this guide. You can also refer to the promotions reference docs for complete information.

Secrets

Secrets are used to store and retrieve sensitive data such as API keys, which should never be committed to source control. Semaphore securely manages sensitive data for use in blocks and tasks via encrypted environment variables or files. You can create a secret using the sem CLI and reference it in the pipeline YML definition.

We will see how to define and use secrets later in this guide. You can refer to the secrets reference docs for more information.

Agents, Machines, and Containers

Semaphore makes sure that there are always agents ready to run all your jobs. When configuring an agent, you can select from a number of memory/CPU combinations and virtual machine (VM) operating system environments.

The Ubuntu Linux and MacOS Mojave VM environments have common build tools and programming languages preinstalled, so you can run your code without an overhead of installing many dependencies in every workflow. Agents provide full sudo access to you so you can install additional software when needed.

Agents can also use custom Docker containers to run your jobs. This is an alternative to using Semaphore VMs which gives you complete control over your CI/CD environment.

Next steps

Let's learn how to customize your pipeline so that it runs the way you want it.

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