Single CI config for multiple repositories - github

Question

seeking for advice about such problem.
We have stack of microservices written on NodeJs and running on Kubernetes cluster. We have separate GitHub repository for each of them and currently using Circleci for our CI/CD process. As of now we have about 25-30 repos, but their number will increase and problem that we faced now is that we need to have Circleci config yaml in each repository and if we need to change something globally in our ci/cd pipeline, we need to update this in each repository, which is obviously pretty painful process and Circleci doesn't support to have one config file for multiple repos.
I believe our situation/setup in terms of multiple repos is not unique, does anybody have experience/ideas of which CI tool support described scenario of having one config file for multiple repos?

Answer 1

Below are 2 approaches that I considered when had to deal with similar situation. You'd need to define for yourself what you want to optimize for and make a decision based on that
Optimizing for flexibility and isolation. In this scenario instead of making all repos use the same config file, you're keeping the file in each repo and automating how you manage this file.
For example: you'll have to create a CLI tool or a script to automate copying circle file and committing to appropriate repos (whenever a change needs to happen)
PROS: isolation - all repos have their own configuration, if you ever going to have a golang microservice or different config in one of your nodejs services, modifying CI pipeline wouldn't be an issue
CONS: a bit of extra work to write automation around managing this config separately
Optimizing for easier maintainability. Figure how to share single pipeline configuration across your repos.
For example: use git submodules for keeping circle.yml file, or use separate npm package with circle.yml file. Another alternative is to use a CI tool that supports templating, then define pipeline template and re-use it for each individual pipeline (one of the CI tools that supports it - Teamcity)
I personally picked approach #1 in similar situation. IMHO, this is a price one have to pay when one decides to go with microservices to not end up with a platform that is rather a distributed monolith :) also I really liked when all repos are descriptive and self contained and CI pipeline as code is one of the ways to help achieve that

Answer 2

In my mind you have 2 options - you could have a single CI job/config that can deploy any single/multiple services (if all the services are the same). Or if every service is different than you need a separate job/config for each. If it's somewhere in the middle it's a question of whether you want a single job that has a bunch of if/then statements e.g. "if repo = user then do this special thing." The if/then approach worked fine for me up to a point, but eventually, there were too many special cases at it was easier to just go with the unique config for each service.
I solved the issue of it "being hard to make a 1 line change across 30 git repos" by having a git superuser. Basically, normal users can only merge using PRs, but the superuser can commit directly. Since I'm only changing things like config files there are rarely merge conflicts or broken test cases so it works. Here's some sample code:
#!/usr/bin/env bash
for dir in /temp/*/
do
cd $dir
git pull
sed 's/Nick/John/g' report.txt > report_new.txt
git commit -m "CI change" && git push
cd ..
done