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2021-10-04{dir,inbox}idle: use level-triggered epoll
Both read(2) on inotify and kevent(2) return a finite amount of events. Let the kernel notify us again in cases where we'd need to retry instead of looping ourselves. This can prevent missed/delayed notifications while still ensuring fairness in busy event loops.
2021-01-01update copyrights for 2021
Using "make update-copyrights" after setting GNULIB_PATH in my config.mak
2020-12-27extindex: --watch for inotify-based updates
This reuses existing InboxIdle infrastructure to update external indices based on per-inbox updates. This is an alternative to auto-updating external indices via the -index command and also works with existing uses of -mda and public-inbox-watch. Using inotify (or EVFILT_VNODE) allows watching thousands of inboxes without having to scan every single one at every invocation. This is especially beneficial in cases where an external index is not writable to the users writing to per-inbox indices.
2020-12-26inboxidle: avoid needless syscalls on refresh
We don't have to replace a bunch of existing watches with identical new ones. On Linux with Linux::Inotify2 installed, this avoids a storm of inotify_add_watch(2) and inotify_rm_watch(2) syscalls on SIGHUP with -imapd and "-extindex --watch"
2020-12-26inboxidle: clue users into resolving ENOSPC from inotify
It may not be obvious to users a ENOSPC error is from hitting a (tunable) kernel-imposed limit on inotify watches, and not some storage device running out of space. Give them a hint here to reduce our own support burden.
2020-12-20inboxidle: remove needless check for {inboxdir}
->each_inbox will never attempt to iterate an object without {inboxdir}, and simplify + short-circuit the corresponding code
2020-12-09rename {pi_config} fields to {pi_cfg}
{pi_config} may be confused with the documented `PI_CONFIG' environment variable, and we'll favor vowel-removal to be consistent with our usage of object references. The `pi_' prefix may stay in some places, for now; since a separate namespace may come into this codebase for local/private client-tooling. For InboxIdle, we'll also remove an invalid comment about holding a reference to the PublicInbox::Config object, too.
2020-07-06inboxidle: warn on inotify_add_watch failures
inotify_add_watch(2), open(2), stat(2) may all fail due to permissions errors, especially when running -nntpd/-imapd as `nobody' as recommended.
2020-07-02inboxidle: avoid per-inbox anonymous subs
Anonymous subs cost over 5K each on x86-64. So prefer the less-recommended-but-still-documented way of using Linux::Inotify2::watch to register watchers. This also updates FakeInotify to detect modifications correctly when used on systems with neither IO::KQueue nor Linux::Inotify2.
2020-06-28ds: remove fields.pm usage
Since the removal of pseudo-hash support in Perl 5.10, the "fields" module no longer provides the space or speed benefits it did in 5.8. It also does not allow for compile-time checks, only run-time checks. To me, the extra developer overhead in maintaining "use fields" args has become a hassle. None of our non-DS-related code uses fields.pm, nor do any of our current dependencies. In fact, Danga::Socket (which DS was originally forked from) and its subclasses are the only fields.pm users I've ever encountered in the wild. Removing fields may make our code more approachable to other Perl hackers. So stop using fields.pm and locked hashes, but continue to document what fields do for non-trivial classes.
2020-06-28watch: remove Filesys::Notify::Simple dependency
Since we already use inotify and EVFILT_VNODE (kqueue) in -imapd, we might as well use them directly in -watch, too. This will allow public-inbox-watch to use PublicInbox::DS for timers to watch newsgroups/mailboxes and have saner signal handling in future commits.
2020-06-25lock: reduce inotify wakeups
We can reduce the amount of platform-specific code by always relying on IN_MODIFY/NOTE_WRITE notifications from lock release. This reduces the number of times our read-only daemons will need to wake up when -watch sees no-op message changes (e.g. replied, seen, recent flag changes).
2020-06-16imap: improve IDLE handling at graceful shutdown
Since IMAP IDLE users aren't expected to issue any commands, we can terminate their connections immediately on graceful shutdown. Furthermore, we need to drop the inotify FD from the epoll set to avoid warnings during global destruction. Embarassingly, this required fixing wacky test ordering from 2a717d13f10fcdc6 ("nntpd+imapd: detect replaced over.sqlite3")
2020-06-15inboxidle: support Linux::Inotify2 1.x
Linux::Inotify2 1.x lacked ->on_overflow and ->broadcast methods. Just don't use them for now. We may eventually provide a pure Perl alternative which doesn't require closures, XS, or the common::sense dependency. Overflowing the inotify queue seems difficult to trigger at the moment: /proc/sys/fs/inotify/max_queued_events defaults to 16384 on a my CentOS 7.x VM with 2GB RAM.
2020-06-13imap: delay InboxIdle start, support refresh
InboxIdle should not be holding onto Inbox objects after the Config object they came from expires, and Config objects may expire on SIGHUP. Old Inbox objects still persist due to IMAP clients holding onto them, but that's a concern we'll deal with at another time, or not at all, since all clients expire, eventually. Regardless, stale inotify watch descriptors should not be left hanging after SIGHUP refreshes.
2020-06-13inboxidle: new class to detect inbox changes
This will be used to implement IMAP IDLE, first. Eventually, it may be used to trigger other things: * incremental internal updates for manifest.js.gz * restart `git cat-file' processes on pack index unlink * IMAP IDLE-like long-polling HTTP endpoint And maybe more things we haven't thought of, yet. It uses Linux::Inotify2 or IO::KQueue depending on what packages are installed and what the kernel supports. It falls back to nanosecond-aware Time::HiRes::stat() (available with Perl 5.10.0+) on systems lacking Linux::Inotify2 and IO::KQueue. In the future, a pure Perl alternative to Linux::Inotify2 may be supplied for users of architectures we already support signalfd and epoll on. v2 changes: - avoid O_TRUNC on lock file - change ctime on Linux systems w/o inotify - fix naming of comments and fields