Since each job runs in a clean and isolated VM, we need to explicitly configure project dependencies. Installing them in every stage and every block from scratch would slow down the pipeline and make it less reliable.
Semaphore includes a tool to cache files and directories backed by an extremely fast network, so even gigabytes may be cached with ease.
Here's an example of installing and caching
npm dependencies in one block, then reusing them in subsequent blocks:
# .semaphore/semaphore.yml agent: machine: type: e1-standard-2 os_image: ubuntu1804 blocks: - name: Install dependencies task: jobs: - name: npm install and cache commands: - checkout - cache restore - npm install - cache store - name: Tests task: prologue: commands: - checkout - cache restore jobs: - name: Everything commands: - npm test
The example above uses a cache command -
cache store and
cache restore. The cache command recognizes the project structure and automatically store and restore dependencies.
If we change any of our dependencies, the content of
package-lock.json will change, and the cache would be invalidated. Since
cache restore does partial matching, Semaphore will attempt to reuse cache from any previous revision of the current Git branch. If there is none, then it will reuse the last available cache created by the master branch.
This strategy ensures best cache hit rate through the lifetime of your project.
Production CI/CD often requires use of environment variables and private API keys. Let's move on to learn how to manage sensitive data and environment variables.