CircleCI allows us to specify a job’s parallelism level. In this post, we will try to further customize that using a custom CircleCI parameter.
Premise
We can use CircleCI’s parallelism feature to split a job in parallel by spreading them across multiple separate executors.
But sometimes we want to customize the parallelism count based on various other parameters.
One example of this would be, let’s say we have two kinds of workflows. A ci-workflow that runs every time. And a nightly workflow that runs at a certain time every night and builds the nightly release.
jobs:
rspec:
executor: rspec-executor
parallelism: 30
steps: ...
workflows:
nightly:
triggers:
- schedule:
cron: "00 10 * * *"
filters:
branches:
only:
- master
jobs:
- rspec:
requires:
- bundle-install
ci-workflow:
jobs:
- rspec:
requires:
- bundle-install
We are using parallelism of 30 for our RSpec tests. For both the workflows. Now nightly runs happen at a low traffic time when most of the devs are asleep. We can reduce the number of parallelism for just the nightly workflow.
Solution
CircleCI does not provide an out-of-the-box solution for the above problem. We will need to rely on a custom parameter to solve this problem.
jobs:
rspec:
executor: rspec-executor
parameters:
machines:
type: integer
default: 30
parallelism: << parameters.machines >>
steps: ...
workflows:
nightly:
triggers:
- schedule:
cron: "00 10 * * *"
filters:
branches:
only:
- master
jobs:
- rspec:
requires:
- bundle-install
ci-workflow:
jobs:
- rspec:
machines: 10
requires:
- bundle-install
Using a pipeline parameter like above we can customize the parallelism value in CircleCI.
Until next time! ❤️
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