quartz/content/notes/11-continuous-integration-2.md

title	sr-due	sr-interval	sr-ease	tags
11-continuous-integration-2	2022-04-07	3	250	cosc202 lecture

1. Apprecitae that GitLab is a complex software
2. Understand where CI jobs scripts get run
3. explain why repository servers can host websites
4. Understand how gitblab dternmimines awhen a CI script failed
5. Describe a way in which CI scripts scan handle secrets
6. Outline uses of local git hook scripts

CI runs pipelines defined in .gitlab-ci.yaml asynchronously

CI usually tests and builds your projects

Runs on a repo server. Usually persistent, internet accessible

1 GitLab overall architecture

: not in exam

• many services used

2 GitLab runners

run CI scripts

• gitlab.com is a cloud computing service
• allows elf hosting which is what CS does
  • altitude is a GitLab instance at CS
    • servers to host runners that run CI scripts
    • servers that host websites, e.g., cspages.otago.nz
• GitLab can invoke runners that you host
  • e.g., to use a particular GPU, or other hardware you have
  • GitLab runner itself is a small program written in Go

2.1 Runner architecture

• runs jobs
  • on isolated infrastructure
  • ... to maintain security
• that is set up on demand
  • ... handle load variation
• suits cloud computing

RHS shows GitLab.com's CI hosting: uses google cloud

: not in exam

3 How CI changed website hosting

• need to share artifacts produced by CI jobs
  • using the web to share artifacts is ideal
  • so now most repo servers also host websites
  • these are static websites: all content is fixed
• CI can run static website generators (SSGs)
  • git repo contains source code of website
  • CI pipelines transforms source code into HTML files
  • HTML files then hosted as a website by repo sever

e.g., https://cosc202.cspages.otago.ac.nz

4 Debugging CI scripts

• First ensure config files YAML is valid
  • built in GitLab editor checks YAML as you type
• commands run from shell that fail return an exit code
  • most Unix shells store exit code of previous commands in $
  • So if variable $? (return code of previous command) is non-zero, the previous command failed
• Git lab considers CI job as failed if any command fails
  • your shell scripting can choose to hide this exit code
    • e.g., if command supposed to fail; then true; else true; fi
  • Complex scripting? Best to put script in a file and run it from CI

5 Secrets used by CI scripts