Don't lose log messages when two Catalyst apps share a process

Changes

@@ -1,3 +1,6 @@
+- fix Log::Log4perl::Catalyst losing log messages when two Catalyst apps
+  share a process - thanks @fleetfootmike
+
 1.57 2022-10-21
 - fix tests so work on Perl 5.37.3 - thanks @tonycoz
 

MANIFEST

@@ -150,6 +150,7 @@ t/067Exception.t
 t/068MultilineIndented.t
 t/069MoreMultiline.t
 t/070UTCDate.t
+t/072Catalyst.t
 t/deeper1.expected
 t/deeper6.expected
 t/deeper7.expected

lib/Log/Log4perl/Catalyst.pm

@@ -88,6 +88,17 @@ sub new {
 
             my $buf_app_name = "$appender->{name}_$CATALYST_APPENDER_SUFFIX";
 
+            # Somebody's already given this appender a buffer, so leave it
+            # alone. Building a second one here would drop it into the
+            # registry on top of the first, but the loggers already writing to
+            # the first one never get moved across, because the loop below
+            # only picks up loggers still on the raw appender. They'd carry on
+            # filling a buffer that _flush() can no longer see, and their
+            # messages would never come out. Happens as soon as two Catalyst
+            # apps share a process and a config.
+            next if exists
+                $Log::Log4perl::Logger::APPENDER_BY_NAME{ $buf_app_name };
+
             my $buf_app = Log::Log4perl::Appender->new(
                 'Log::Log4perl::Appender::Buffer',
                 name       => $buf_app_name,

t/072Catalyst.t

@@ -0,0 +1,55 @@
+###########################################
+# Test Suite for Log::Log4perl::Catalyst
+###########################################
+
+BEGIN {
+    if($ENV{INTERNAL_DEBUG}) {
+        require Log::Log4perl::InternalDebug;
+        Log::Log4perl::InternalDebug->enable();
+    }
+}
+
+use strict;
+use warnings;
+use Test::More;
+
+use Log::Log4perl;
+use Log::Log4perl::Catalyst;
+use Log::Log4perl::Appender::TestBuffer;
+
+my $conf = qq(
+log4perl.category            = DEBUG, Root
+log4perl.appender.Root        = Log::Log4perl::Appender::TestBuffer
+log4perl.appender.Root.layout = SimpleLayout
+
+log4perl.logger.api          = INFO, Api
+log4perl.additivity.api      = 0
+log4perl.appender.Api        = Log::Log4perl::Appender::TestBuffer
+log4perl.appender.Api.layout = SimpleLayout
+);
+
+# Mount two Catalyst apps in the one process, which is ordinary enough under
+# Plack::Builder, and they'll each build a logger from the same config. That's
+# all this is doing.
+#
+# With autoflush off, the constructor sticks a buffer in front of every
+# appender and tells the loggers to write to the buffer instead. Do that twice
+# and the second time round builds a fresh set of buffers, drops them into the
+# registry on top of the old ones, and then only fixes up the loggers that are
+# still writing to the raw appender. Any logger the first pass already moved is
+# left behind, still writing to a buffer that nothing can get at any more.
+# _flush() goes through the registry, so it empties the new buffers while the
+# message is sat in the old one, and the line just quietly vanishes.
+my $app1_log = Log::Log4perl::Catalyst->new(\$conf);
+my $app2_log = Log::Log4perl::Catalyst->new(\$conf);
+
+Log::Log4perl->get_logger("api")->info("a logged message");
+
+# What Catalyst::handle_request() does after finalize on every request.
+$app2_log->_flush();
+
+like(Log::Log4perl::Appender::TestBuffer->by_name("Api")->buffer(),
+     qr/a logged message/,
+     "message survives a second Log::Log4perl::Catalyst construction");
+
+done_testing();