From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: X-Spam-Status: No, score=-4.0 required=3.0 tests=ALL_TRUSTED,BAYES_00 shortcircuit=no autolearn=ham autolearn_force=no version=3.4.2 Received: from localhost (dcvr.yhbt.net [127.0.0.1]) by dcvr.yhbt.net (Postfix) with ESMTP id D7CF61F4C0 for ; Thu, 3 Oct 2019 07:22:01 +0000 (UTC) From: Eric Wong To: meta@public-inbox.org Subject: [PATCH 3/3] init: implement locking Date: Thu, 3 Oct 2019 07:21:59 +0000 Message-Id: <20191003072159.84408-4-e@80x24.org> In-Reply-To: <20191003072159.84408-1-e@80x24.org> References: <20191003072159.84408-1-e@80x24.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit List-Id: First, we use flock(2) to wait on parallel public-inbox-init(1) invocations while we make multiple changes using git-config(1). This flock allows -init processes to wait on each other if using reasonable POSIX filesystems. Then, we also need a git-config(1)-compatible lock to prevent user-invoked git-config(1) processes from clobbering our changes while we're holding the flock. --- script/public-inbox-init | 24 ++++++++++++++++++++++++ t/init.t | 12 ++++++++++++ 2 files changed, 36 insertions(+) diff --git a/script/public-inbox-init b/script/public-inbox-init index 39f2a067..8fd2f9dc 100755 --- a/script/public-inbox-init +++ b/script/public-inbox-init @@ -12,8 +12,10 @@ PublicInbox::Admin::require_or_die('-base'); require PublicInbox::Config; require PublicInbox::InboxWritable; use File::Temp qw/tempfile/; +use PublicInbox::Lock; use File::Basename qw/dirname/; use File::Path qw/mkpath/; +use Fcntl qw(:DEFAULT); use Cwd qw/abs_path/; sub x { system(@_) and die join(' ', @_). " failed: $?\n" } @@ -38,7 +40,29 @@ my %seen; my $pi_config = PublicInbox::Config->default_file; my $dir = dirname($pi_config); mkpath($dir); # will croak on fatal errors + +# first, we grab a flock to prevent simultaneous public-inbox-init +# processes from trampling over each other, or exiting with 255 on +# O_EXCL failure below. This gets unlocked automatically on exit: +my $lock_obj = { lock_path => "$pi_config.flock" }; +PublicInbox::Lock::lock_acquire($lock_obj); + +# git-config will operate on this (and rename on success): my ($fh, $pi_config_tmp) = tempfile('pi-init-XXXXXXXX', DIR => $dir); + +# Now, we grab another lock to use git-config(1) locking, so it won't +# wait on the lock, unlike some of our internal flock()-based locks. +# This is to prevent direct git-config(1) usage from clobbering our +# changes. +my $lockfile = "$pi_config.lock"; +my $lockfh; +sysopen($lockfh, $lockfile, O_RDWR|O_CREAT|O_EXCL) or do { + $lockfh = undef; + warn "could not open config file: $lockfile: $!\n"; + exit(255); +}; +END { unlink($lockfile) if $lockfh }; + my $perm; if (-e $pi_config) { open(my $oh, '<', $pi_config) or die "unable to read $pi_config: $!\n"; diff --git a/t/init.t b/t/init.t index 667b09fe..0cd6f31f 100644 --- a/t/init.t +++ b/t/init.t @@ -10,6 +10,8 @@ my $tmpdir = tempdir('pi-init-XXXXXX', TMPDIR => 1, CLEANUP => 1); use constant pi_init => 'blib/script/public-inbox-init'; use PublicInbox::Import; use File::Basename; +use PublicInbox::Spawn qw(spawn); +use Cwd qw(getcwd); open my $null, '>>', '/dev/null'; my $rdr = { 2 => fileno($null) }; sub quiet_fail { @@ -47,6 +49,16 @@ sub quiet_fail { @cmd = (pi_init, 'clist', '-V2', "$tmpdir/clist", qw(http://example.com/clist clist@example.com)); quiet_fail(\@cmd, 'attempting to init V2 from V1 fails'); + + open my $lock, '+>', "$cfgfile.lock" or die; + @cmd = (getcwd(). '/'. pi_init, 'lock', "$tmpdir/lock", + qw(http://example.com/lock lock@example.com)); + ok(-e "$cfgfile.lock", 'lock exists'); + my $pid = spawn(\@cmd, undef, $rdr); + is(waitpid($pid, 0), $pid, 'lock init failed'); + is($? >> 8, 255, 'got expected exit code on lock failure'); + ok(unlink("$cfgfile.lock"), + '-init did not unlink lock on failure'); } SKIP: { -- EW