fix #2821: only abort if there really is a waiting/syncing job

by remembering the process via PID+start time+boot ID and checking for that
information in the new instance. If the old instance can't be found, the new
one will continue and register itself in the state.

After updating the pve-zsync package, if there is a waiting instance running the
old version, one more might be created, because there is no instance_id yet. But
the new instance will set the instance_id, which any later instance will see.

More importantly, if the state is wrongly 'waiting' or 'syncing', i.e.
because an instance was terminated before finishing, we don't abort anymore and
recover from the wrong state, thus fixing the bug.

Signed-off-by: Fabian Ebner <f.ebner@proxmox.com>

diff --git a/pve-zsync b/pve-zsync
index 76e12ced9e0e199b6fdea38e6e856e00e4ed5fb3..5c959552ed97292389c0f6d33a8edb06fbb29482 100755 (executable)
--- a/pve-zsync
+++ b/pve-zsync
@@ -55,6 +55,8 @@ my $TARGETRE = qr!^(?:($HOSTRE):)?(\d+|(?:[\w\-_]+)(/.+)?)$!;
 
 my $DISK_KEY_RE = qr/^(?:(?:(?:virtio|ide|scsi|sata|efidisk|mp)\d+)|rootfs): /;
 
+my $INSTANCE_ID = get_instance_id($$);
+
 my $command = $ARGV[0];
 
 if (defined($command) && $command ne 'help' && $command ne 'printpod') {
@@ -274,6 +276,7 @@ sub add_state_to_job {
     $job->{state} = $state->{state};
     $job->{lsync} = $state->{lsync};
     $job->{vm_type} = $state->{vm_type};
+    $job->{instance_id} = $state->{instance_id};
 
     for (my $i = 0; $state->{"snap$i"}; $i++) {
        $job->{"snap$i"} = $state->{"snap$i"};
@@ -359,6 +362,7 @@ sub update_state {
     if ($job->{state} ne "del") {
        $state->{state} = $job->{state};
        $state->{lsync} = $job->{lsync};
+       $state->{instance_id} = $job->{instance_id};
        $state->{vm_type} = $job->{vm_type};
 
        for (my $i = 0; $job->{"snap$i"} ; $i++) {
@@ -571,6 +575,33 @@ sub destroy_job {
     });
 }
 
+sub get_instance_id {
+    my ($pid) = @_;
+
+    my $stat = read_file("/proc/$pid/stat", 1)
+       or die "unable to read process stats\n";
+    my $boot_id = read_file("/proc/sys/kernel/random/boot_id", 1)
+       or die "unable to read boot ID\n";
+
+    my $stats = [ split(/\s+/, $stat) ];
+    my $starttime = $stats->[21];
+    chomp($boot_id);
+
+    return "${pid}:${starttime}:${boot_id}";
+}
+
+sub instance_exists {
+    my ($instance_id) = @_;
+
+    if (defined($instance_id) && $instance_id =~ m/^([1-9][0-9]*):/) {
+       my $pid = $1;
+       my $actual_id = eval { get_instance_id($pid); };
+       return defined($actual_id) && $actual_id eq $instance_id;
+    }
+
+    return 0;
+}
+
 sub sync {
     my ($param) = @_;
 
@@ -580,11 +611,16 @@ sub sync {
        eval { $job = get_job($param) };
 
        if ($job) {
-           if (defined($job->{state}) && ($job->{state} eq "syncing" || $job->{state} eq "waiting")) {
+           my $state = $job->{state} // 'ok';
+           $state = 'ok' if !instance_exists($job->{instance_id});
+
+           if ($state eq "syncing" || $state eq "waiting") {
                die "Job --source $param->{source} --name $param->{name} is already scheduled to sync\n";
            }
 
            $job->{state} = "waiting";
+           $job->{instance_id} = $INSTANCE_ID;
+
            update_state($job);
        }
     });
@@ -658,6 +694,7 @@ sub sync {
                eval { $job = get_job($param); };
                if ($job) {
                    $job->{state} = "error";
+                   delete $job->{instance_id};
                    update_state($job);
                }
            });
@@ -674,6 +711,7 @@ sub sync {
                    $job->{state} = "ok";
                }
                $job->{lsync} = $date;
+               delete $job->{instance_id};
                update_state($job);
            }
        });