gdb-bof-cauldron-2019/gdb-bof-cauldron-2019.org

#+OPTIONS: toc:nil date:nil
#+CREATOR: Emacs 26.1 (Org mode 9.1.9)
#+TITLE: GDB tests, CI & Buildbot BoF
#+AUTHOR: Sergio Durigan Junior @@latex:\\@@ sergiodj@redhat.com
#+LANGUAGE: en

* License

- License: *Creative Commons Attribution 4.0 International License (CC-BY-4.0)*

- https://creativecommons.org/licenses/by/4.0/

* Nomenclature

- *Worker*: The node that performs the “build”.  Usually one per
  physical machine/VM.  For example, =fedora-x86_64-1= or
 =ubuntu-aarch64=.

- *Factory*: A recipe of how to perform a build.

- *Builder*: An instance of a factory.  For example,
 =Fedora-x86_64-m64= or
 =Ubuntu-Aarch64-native-extended-gdbserver-m64=.

- *Scheduler*: Dispatches jobs to a set of builders.  Can be triggered
  by specific events like a commit in a repository, a /try build/
  request or like a cronjob.

* How was it?

- GDB Buildbot started in 2015 as a personal project.

#+BEAMER: \pause

- We just had *2* machines serving *4* Fedora =x86_64= workers at the
  time.  And no /try builds/!

#+BEAMER: \pause

- Initially it stored the test results in a git repository.  This
  proved too inefficient over time...

* And now?

- The master runs in a dedicated VM at *OSCI* (@@latex:\textbf{O}@@pen
  @@latex:\textbf{S}@@ource @@latex:\textbf{C}@@ommunity
  @@latex:\textbf{I}@@nfrastructure).

#+BEAMER: \pause

- Most of our builders support /try builds/!

#+BEAMER: \pause

- *14* workers (*11* machines):

  #+BEAMER: \pause

  - Sergio (Red Hat): *2* machines (Fedora =x86_64=)

  - Alan Hayward (ARM): *2* machines (Ubuntu =ARM 32= and =64=)

  - Rainer Orth (CeBiTec.Uni-Bielefeld.DE): *2* machines (Solaris
 =amd64= and =sparcv9=)

  - David Edelsohn: *3* machines (RHEL 7.1 =s390x=, AIX =POWER8= and
    Debian Jessie =s390x=)

  - Edjunior Machado: *1* machine (CentOS 7 =PPC64LE=)

  - Mark Wielaard: *1* machine (Fedora =s390x=)

  - Kamil Rytarowski: *1* machine (NetBSD =amd64=)

#+BEAMER: \pause

- Test results are stored directly on-disk, and “garbage-collected”
  every week (tests older than 4 months are deleted).

* How does it work?

[[file:submit-patch.png]]

* How does it work? @@latex:$^2$@@

#+ATTR_LATEX: :width 0.5\textwidth
[[file:build-steps.png]]

* Racy tests handling (or an attempt to)

- We keep a list of racy tests (detected weekly through the racy
  build analysis).

#+BEAMER: \pause

- When a racy build finishes, we include the racy tests in the =xfail=
  file for that builder.

#+BEAMER: \pause

- We then ignore them when doing normal test builds.  However...
  whac-a-mole.

* Test analysis (a.k.a. finding regressions)

- Transform the current =.sum= file into a Python dict:

  - ~{ 'gdb.base/test1.exp: name1' : 'PASS', 'gdb.base/test1.exp: name2' : 'FAIL', ...}~

#+BEAMER: \pause

- Do the same for the previous =.sum= file.

#+BEAMER: \pause

- Iterate over the current =.sum= file's dictionary and do:

  #+BEAMER: \pause

  - If the current key is =XFAIL='ed (i.e., a racy test), ignore it.

  #+BEAMER: \pause

  - If the current key exists in the new dict:

    - If it has the same value, good (not a regression).

    - If it changed from =PASS= to =FAIL=, bad.  Report as a
      regression.

    - If it changed from =FAIL= to =PASS=, good.  Update the baseline.

  #+BEAMER: \pause

  - If the current key doesn't exist in the new dict:

    - If it's a =PASS=, good.  Update the baseline.

    - If it's a =FAIL=, bad.  Report as a new failure.

* Notifications

- To /gdb-testers/: whenever we detect a possible regression in an
  upstream commit.

#+BEAMER: \pause

- To the /author/: on /try builds/, or when his/her commit broke GDB.

#+BEAMER: \pause

- To /gdb-patches/: when a commit breaks GDB.

#+BEAMER: \pause

- Breakage notifications are usually reliable.  Regression
  notifications are not (just look at /gdb-testers/).

* Problems and challenges

- Racy testcases.  Perhaps the most difficult/persistent problem?

#+BEAMER: \pause

- Lots of test messages are non-unique.  This makes it really hard to
  compare test results and find regressions.

#+BEAMER: \pause

- Better way to store and retrieve test results (current way is
  “enough” for what we need, but it can certainly be improved).  See
  Serhei's work and Keith's work.

#+BEAMER: \pause

- =make -jN=, racy tests and =gdb.threads=.