diff --git a/lib/core_ext/logger/formatter.rb b/lib/core_ext/logger/formatter.rb
new file mode 100644
index 000000000..fdc88c5b8
--- /dev/null
+++ b/lib/core_ext/logger/formatter.rb
@@ -0,0 +1,20 @@
+# This customization adds the id of the current Thread to all log lines.
+# It was introduced to make it more easy to follow the execution of tasks in the log in threaded processes.
+#
+# before:
+# D, [2018-11-20T16:35:03.483547 #72102] DEBUG -- :    (0.5ms)  SELECT COUNT(*) FROM "delayed_jobs"
+#
+# after:
+# D, [2018-11-20T16:35:03.483547 #72102-23423534] DEBUG -- :    (0.5ms)  SELECT COUNT(*) FROM "delayed_jobs"
+
+class Logger
+  class Formatter
+
+    # original: Format    = "%s, [%s#%d] %5s -- %s: %s\n".freeze
+    FORMAT_WITH_THREAD_ID = "%s, [%s#%d-%d] %5s -- %s: %s\n".freeze
+
+    def call(severity, time, progname, msg)
+      format(FORMAT_WITH_THREAD_ID, severity[0..0], format_datetime(time), Process.pid, Thread.current.object_id, severity, progname, msg2str(msg))
+    end
+  end
+end