From 35e31227139e401cf7845d824a1b4e6a1de56fe3 Mon Sep 17 00:00:00 2001 From: Eric Wong Date: Sat, 27 Jun 2020 10:03:59 +0000 Subject: imaptracker: use flock(2) around writes SQLite only issues non-blocking F_SETLK ops (not F_SETLKW) and retries failures using a configurable busy_timeout. SQLite's busy loop sleeps for a millisecond and retries the lock until the configured busy_timeout is hit. Trying to set ->sqlite_busy_timeout to larger values (e.g. 30000 milliseconds) still leads to failure when running the new stress test with 8 processes with TMPDIR on a 7200 RPM HDD. Inspection of SQLite source reveals there's no built-in way to use F_SETLKW, so tack on the existing flock(2) support we use to synchronize git + SQLite + Xapian for inbox writing. We use flock(2) instead of POSIX fcntl(2) locks since Perl doesn't provide a way to manipulate "struct flock" portably. --- lib/PublicInbox/IMAPTracker.pm | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) (limited to 'lib') diff --git a/lib/PublicInbox/IMAPTracker.pm b/lib/PublicInbox/IMAPTracker.pm index 0bbabe07..102a74ce 100644 --- a/lib/PublicInbox/IMAPTracker.pm +++ b/lib/PublicInbox/IMAPTracker.pm @@ -2,6 +2,7 @@ # License: AGPL-3.0+ package PublicInbox::IMAPTracker; use strict; +use parent qw(PublicInbox::Lock); use DBI; use DBD::SQLite; use PublicInbox::Config; @@ -48,7 +49,10 @@ sub update_last ($$$) { INSERT OR REPLACE INTO imap_last (url, uid_validity, uid) VALUES (?, ?, ?) - $sth->execute($self->{url}, $validity, $last); + $self->lock_acquire; + my $rv = $sth->execute($self->{url}, $validity, $last); + $self->lock_release; + $rv; } sub new { @@ -68,8 +72,11 @@ sub new { require File::Basename; File::Path::mkpath(File::Basename::dirname($dbname)); } - - bless { url => $url, dbh => dbh_new($dbname) }, $class; + my $self = bless { lock_path => "$dbname.lock", url => $url }, $class; + $self->lock_acquire; + $self->{dbh} = dbh_new($dbname); + $self->lock_release; + $self; } 1; -- cgit v1.2.3-24-ge0c7