[pmg-devel] [PATCH pmg-api v2] adapt journalctl invocation to buster

[Stoiko Ivanov]

With Debian Buster the behavior of `journalctl` has changed when it finds
no entries for a given selection:
* The exit code was 0 in stretch, but is 1 in buster
* The output changed slightly - a header got added

Since PMG::Utils::scan_journal_for_rbl_rejects uses journalctl for reading the
IPs blocked by postscreen it needs to adapt for the new behavior (otherwise
run_command dies because of the exit code 1)

The patch addresses the problem by using the json-output of `journalctl`, which
still exits with 0 if no entries are present . Additionally the json-output
adds the current cursor to the output by default, removing the need to
explicitly scanning for it.(the exit code of 1 was due to '--show-cursor'
without a single result line).

Signed-off-by: Stoiko Ivanov <s.ivanov at proxmox.com>
---
changes v1->v2:
* Adapted Dominik and Fabian's feedback by using journalctl's json output
* without '--show-cursor' the exit status is '0' even if no entries are
  present
 src/PMG/Utils.pm | 18 ++++++++----------
 1 file changed, 8 insertions(+), 10 deletions(-)

diff --git a/src/PMG/Utils.pm b/src/PMG/Utils.pm
index aa6aac7..65684b6 100644
--- a/src/PMG/Utils.pm
+++ b/src/PMG/Utils.pm
@@ -27,6 +27,7 @@ use utf8;
 no utf8;
 
 use HTML::Entities;
+use JSON;
 
 use PVE::ProcFSTools;
 use PVE::Network;
@@ -1300,23 +1301,20 @@ sub scan_journal_for_rbl_rejects {
     my $pregreet_count = 0;
 
     my $parser = sub {
-	my $line = shift;
-
-	if ($line =~ m/^--\scursor:\s(\S+)$/) {
-	    $rbl_scan_last_cursor = $1;
-	    return;
-	}
+	my $log = decode_json(shift);
 
-	if ($line =~ m/\s$identifier\[\d+\]:\sNOQUEUE:\sreject:.*550 5.7.1 Service unavailable;/) {
+	$rbl_scan_last_cursor = $log->{__CURSOR};
+	my $message = $log->{MESSAGE};
+	if ($message =~ m/^NOQUEUE:\sreject:.*550 5.7.1 Service unavailable/) {
 	    $rbl_count++;
-	} elsif ($line =~ m/\s$identifier\[\d+\]:\sPREGREET\s\d+\safter\s/) {
+	} elsif ($message =~ m/^PREGREET\s\d+\safter\s/) {
 	    $pregreet_count++;
 	}
     };
 
     # limit to last 5000 lines to avoid long delays
-    my $cmd = ['journalctl', '--show-cursor', '-o', 'short-unix', '--no-pager',
-	       '--identifier', $identifier, '-n', 5000];
+    my $cmd = ['journalctl', '-o', 'json', '--output-fields', '__CURSOR,MESSAGE',
+	'--no-pager', '--identifier', $identifier, '-n', 5000];
 
     if (defined($rbl_scan_last_cursor)) {
 	push @$cmd, "--after-cursor=${rbl_scan_last_cursor}";
-- 
2.20.1