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e362fe9c6d
fixes #232505 Implements the new option `security.acme.maxConcurrentRenewals` to limit the number of certificate generation (or renewal) jobs that can run in parallel. This avoids overloading the system resources with many certificates or running into acme registry rate limits and network timeouts. Architecture considerations: - simplicity, lightweight: Concerns have been voiced about making this already rather complex module even more convoluted. Additionally, locking solutions shall not significantly increase performance and footprint of individual job runs. To accomodate these concerns, this solution is implemented purely in Nix, bash, and using the light-weight `flock` util. To reduce complexity, jobs are already assigned their lockfile slot at system build time instead of dynamic locking and retrying. This comes at the cost of not always maxing out the permitted concurrency at runtime. - no stale locks: Limiting concurrency via locking mechanism is usually approached with semaphores. Unfortunately, both SysV as well as POSIX-Semaphores are *not* released when the process currently locking them is SIGKILLed. This poses the danger of stale locks staying around and certificate renewal being blocked from running altogether. `flock` locks though are released when the process holding the file descriptor of the lock file is KILLed or terminated. - lockfile generation: Lock files could either be created at build time in the Nix store or at script runtime in a idempotent manner. While the latter would be simpler to achieve, we might exceed the number of permitted concurrent runs during a system switch: Already running jobs are still locked on the existing lock files, while jobs started after the system switch will acquire locks on freshly created files, not being blocked by the still running services. For this reason, locks are generated and managed at runtime in the shared state directory `/var/lib/locks/`. nixos/security/acme: move locks to /run also, move over permission and directory management to systemd-tmpfiles nixos/security/acme: fix some linter remarks in my code there are some remarks left for existing code, not touching that nixos/security/acme: redesign script locking flow - get rid of subshell - provide function for wrapping scripts in a locked environment nixos/acme: improve visibility of blocking on locks nixos/acme: add smoke test for concurrency limitation heavily inspired by m1cr0man nixos/acme: release notes entry on new concurrency limits nixos/acme: cleanup, clarifications |
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| administration | ||
| configuration | ||
| development | ||
| installation | ||
| release-notes | ||
| common.nix | ||
| contributing-to-this-manual.chapter.md | ||
| default.nix | ||
| manual.md | ||
| nixos-options.md | ||
| preface.md | ||
| README.md | ||
| shell.nix | ||