An HTTP propagator to handle inject/extract

Author: pglombardo

instana/propagator.py

@@ -0,0 +1,38 @@
+from __future__ import absolute_import
+
+import opentracing as ot
+
+prefix_tracer_state = 'HTTP_X_INSTANA_'
+field_name_trace_id = prefix_tracer_state + 'T'
+field_name_span_id = prefix_tracer_state + 'S'
+field_count = 2
+
+
+class HTTPPropagator():
+    """A Propagator for Format.TEXT_MAP."""
+
+    def inject(self, span_context, carrier):
+        carrier[field_name_trace_id] = '{0:x}'.format(span_context.trace_id)
+        carrier[field_name_span_id] = '{0:x}'.format(span_context.span_id)
+
+    def extract(self, carrier):  # noqa
+        count = 0
+        span_id, trace_id = (0, 0)
+        for k in carrier:
+            v = carrier[k]
+            k = k.lower()
+            if k == field_name_span_id:
+                span_id = int(v, 16)
+                count += 1
+            elif k == field_name_trace_id:
+                trace_id = int(v, 16)
+                count += 1
+
+        if count != field_count:
+            raise ot.SpanContextCorruptedException()
+
+        return ot.SpanContext(
+            span_id=span_id,
+            trace_id=trace_id,
+            baggage={},
+            sampled=True)