Syslogging must be exclusive to process

lib/log4r/outputter/syslogoutputter.rb

@@ -15,6 +15,8 @@ module Log4r
 
   class SyslogOutputter < Outputter
     include Syslog::Constants
+
+    SEMAPHOR = Mutex.new()
 
     # maps default log4r levels to syslog priorities (logevents never see ALL and OFF)
     # SYSLOG Levels are:
@@ -118,8 +120,16 @@ def canonical_log(logevent)
 	msg = o.inspect
       end
 
-      Syslog.open(@ident, @logopt, @facility) do |s|
-        s.log(pri, '%s', msg)
+      #Block globally, since the Syslog gets opened for the process
+      SEMAPHOR.synchronize do
+        Syslog.open(@ident, @logopt, @facility) do |s|
+          s.mask = begin
+            Syslog::LOG_UPTO(SYSLOG_LEVELS_MAP[@levels_map[Log4r::LNAMES[@level]]])
+          rescue
+            Syslog::LOG_UPTO(LOG_INFO)
+          end
+          s.log(pri, '%s', msg)
+        end
       end
     end
   end

tests/testsyslogoutputter.rb

@@ -0,0 +1,32 @@
+require 'test_helper'
+require 'log4r/outputter/syslogoutputter'
+
+class TestSyslogOutputter < TestCase
+  def test_concurrency
+    threads = []
+    (1..20).each do
+      threads << Thread.new do
+        #Create log and add syslog outputter
+        id = Thread.current.__id__
+        id = id.to_s()
+        log = Log4r::Logger.new(id)
+        log.add(Log4r::SyslogOutputter.new(id))
+
+        (1..200).each do
+          log.debug "debugging"
+          log.info "a piece of info"
+          log.warn "Danger, Will Robinson, danger!"
+          log.error "I dropped my Wookie! :("
+          log.fatal "kaboom!"
+          Thread.pass()
+        end
+      end
+    end
+
+    threads.each do |thread|
+      assert_nothing_raised(Exception) do
+        thread.join()
+      end
+    end
+  end
+end