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

title	draft	sr-due	sr-interval	sr-ease
Lecture 11 Continuous Integration 2	true	2022-04-07	3	250

#review

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1. apprecitae that gitlab is a xomplex software
2. Understand where CI jobs scripts get run
3. explain why reposityory servers can host websites
4. Understandhow gitblab dternmimines awhen a CI script failed
5. Describe a way in which CI scrupts scan handle secrets
6. OUtline uses of local git hook scripts

Lecture 11 Continuous Integration 2

Ci runs pipellines defined in .gitlab-ci.yaml asynchronously

ci usually tets abd buiolds your prokects

runs on a repo server

• usuially persistent, internet accessible

1 Gitlab overall architecture

: not in exam

• many different 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 secrity
• 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 chagned website hosting

• need to share stifacts produced by CI jobs
  • using the web to share artefacts 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 souce code into HTML fiels
  • 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
  • vuilt in gitlab editor checks YAML as you type
• commands runfrom shell that fail return an exit code
  • most unix shells sotre exit code of previous commands in $
  • So if variable $? (return code of prevous 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? Beste to put script in a file and run it from CI

5 Secrets used by CI scripts