diff --git a/contrib/opentracing/include/debug.h b/contrib/opentracing/include/debug.h
new file mode 100644
index 0000000..7becdf7
--- /dev/null
+++ b/contrib/opentracing/include/debug.h
@@ -0,0 +1,96 @@
+/***
+ * Copyright 2020 HAProxy Technologies
+ *
+ * This file is part of the HAProxy OpenTracing filter.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ */
+#ifndef _OPENTRACING_DEBUG_H_
+#define _OPENTRACING_DEBUG_H_
+
+#ifdef DEBUG_FULL
+#  define DEBUG_OT
+#endif
+
+#ifdef DEBUG_OT
+#  ifdef DEBUG_OT_SYSTIME
+#     define FLT_OT_DBG_FMT(f)      "[% 2d] %ld.%06ld [" FLT_OT_SCOPE "]: " f, tid, now.tv_sec, now.tv_usec
+#  else
+#     define FLT_OT_DBG_FMT(f)      "[% 2d] %11.6f [" FLT_OT_SCOPE "]: " f, tid, FLT_OT_TV_UDIFF(&(flt_ot_debug.start), &now) / 1e6
+#  endif
+#  define FLT_OT_DBG_INDENT         "                                                                                "
+#  define FLT_OT_DBG(l,f, ...)                                                             \
+	do {                                                                               \
+		if (!(l) || (flt_ot_debug.level & (1 << (l))))                             \
+			(void)fprintf(stderr, FLT_OT_DBG_FMT("%.*s" f "\n"),               \
+			              dbg_indent_level, FLT_OT_DBG_INDENT, ##__VA_ARGS__); \
+	} while (0)
+#  define FLT_OT_FUNC(f, ...)       do { FLT_OT_DBG(1, "%s(" f ") {", __func__, ##__VA_ARGS__); dbg_indent_level += 3; } while (0)
+#  define FLT_OT_RETURN(a)          do { dbg_indent_level -= 3; FLT_OT_DBG(1, "}"); return a; } while (0)
+#  define FLT_OT_DBG_IFDEF(a,b)     a
+#  define FLT_OT_DBG_ARGS(a, ...)   a, ##__VA_ARGS__
+
+struct flt_ot_debug {
+#ifndef DEBUG_OT_SYSTIME
+	struct timeval start;
+#endif
+	uint8_t        level;
+};
+
+
+extern THREAD_LOCAL int    dbg_indent_level;
+extern struct flt_ot_debug flt_ot_debug;
+
+#else
+
+#  define FLT_OT_DBG(...)           while (0)
+#  define FLT_OT_FUNC(...)          while (0)
+#  define FLT_OT_RETURN(a)          return a
+#  define FLT_OT_DBG_IFDEF(a,b)     b
+#  define FLT_OT_DBG_ARGS(...)
+#endif /* DEBUG_OT */
+
+/*
+ *  ON  | NOLOGNORM |
+ * -----+-----------+-------------
+ *   0  |     0     |  no log
+ *   0  |     1     |  no log
+ *   1  |     0     |  log all
+ *   1  |     1     |  log errors
+ * -----+-----------+-------------
+ */
+#define FLT_OT_LOG(l,f, ...)                                                                                                    \
+	do {                                                                                                                    \
+		if (!(conf->tracer->logging & FLT_OT_LOGGING_ON))                                                               \
+			FLT_OT_DBG(3, "NOLOG[%d]: [" FLT_OT_SCOPE "]: [%s] " f, (l), conf->id, ##__VA_ARGS__);                  \
+		else if ((conf->tracer->logging & FLT_OT_LOGGING_NOLOGNORM) && ((l) > LOG_ERR))                                 \
+			FLT_OT_DBG(2, "NOLOG[%d]: [" FLT_OT_SCOPE "]: [%s] " f, (l), conf->id, ##__VA_ARGS__);                  \
+		else {                                                                                                          \
+			send_log(&(conf->tracer->proxy_log), (l), "[" FLT_OT_SCOPE "]: [%s] " f "\n", conf->id, ##__VA_ARGS__); \
+                                                                                                                                \
+			FLT_OT_DBG(1, "LOG[%d]: %s", (l), logline);                                                             \
+		}                                                                                                               \
+	} while (0)
+
+#endif /* _OPENTRACING_DEBUG_H_ */
+
+/*
+ * Local variables:
+ *  c-indent-level: 8
+ *  c-basic-offset: 8
+ * End:
+ *
+ * vi: noexpandtab shiftwidth=8 tabstop=8
+ */