added experimental backtrace API

[jsteemann]

Scope & Purpose

Experimental backtrace API for the threads in an arangod process.

By sending the arangod process a SIGUSR1 signal, it will make all its threads log a backtrace. It does so by enumerating the list of current threads via reading the fds in /proc/<pid>/task and using the tgkill syscall to deliver a SIGUSR2 signal to each thread. When a thread receives a SIGUSR2 signal, it will log its own backtrace to the log.

This functionality is currently only available on Linux. it is highly experimental and may not work in some environments (e.g. libmusl builds).

• [ ] :hankey: Bugfix
• [x] :pizza: New feature
• [ ] :fire: Performance improvement
• [ ] :hammer: Refactoring/simplification

Checklist

• [ ] Tests
  • [ ] Regression tests
  • [ ] C++ Unit tests
  • [ ] integration tests
  • [ ] resilience tests
• [ ] :book: CHANGELOG entry made
• [ ] :books: documentation written (release notes, API changes, ...)
• [ ] Backports
  • [ ] Backport for 3.11: -
  • [ ] Backport for 3.10: -
  • [ ] Backport for 3.9: -

Related Information

• [ ] Docs PR:
• [ ] Enterprise PR:
• [ ] GitHub issue / Jira ticket:
• [ ] Design document: