Make zipkin tag value length configurable

Zipkin exporter truncates tag values to a maximum length of 128
characters. This commit makes this value configurable while keeping
128 as the default value.

exporter/opentelemetry-exporter-zipkin/CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## Unreleased
 
+- Zipkin exporter now accepts a ``max_tag_value_length`` attribute to customize the maximum allowed size a tag value can have.
+
 ## Version 0.13b0
 
 Released 2020-09-17

exporter/opentelemetry-exporter-zipkin/src/opentelemetry/exporter/zipkin/__init__.py

@@ -74,6 +74,7 @@
 
 DEFAULT_RETRY = False
 DEFAULT_URL = "http://localhost:9411/api/v2/spans"
+DEFAULT_MAX_TAG_VALUE_LENGTH = 128
 ZIPKIN_HEADERS = {"Content-Type": "application/json"}
 
 SPAN_KIND_MAP = {
@@ -108,6 +109,7 @@ def __init__(
         ipv4: Optional[str] = None,
         ipv6: Optional[str] = None,
         retry: Optional[str] = DEFAULT_RETRY,
+        max_tag_value_length=DEFAULT_MAX_TAG_VALUE_LENGTH,
     ):
         self.service_name = service_name
         if url is None:
@@ -122,6 +124,7 @@ def __init__(
         self.ipv4 = ipv4
         self.ipv6 = ipv6
         self.retry = retry
+        self.max_tag_value_length = max_tag_value_length
 
     def export(self, spans: Sequence[Span]) -> SpanExportResult:
         zipkin_spans = self._translate_to_zipkin(spans)
@@ -141,6 +144,9 @@ def export(self, spans: Sequence[Span]) -> SpanExportResult:
             return SpanExportResult.FAILURE
         return SpanExportResult.SUCCESS
 
+    def shutdown(self) -> None:
+        pass
+
     def _translate_to_zipkin(self, spans: Sequence[Span]):
 
         local_endpoint = {"serviceName": self.service_name, "port": self.port}
@@ -171,8 +177,10 @@ def _translate_to_zipkin(self, spans: Sequence[Span]):
                 "duration": duration_mus,
                 "localEndpoint": local_endpoint,
                 "kind": SPAN_KIND_MAP[span.kind],
-                "tags": _extract_tags_from_span(span),
-                "annotations": _extract_annotations_from_events(span.events),
+                "tags": self._extract_tags_from_span(span),
+                "annotations": self._extract_annotations_from_events(
+                    span.events
+                ),
             }
 
             if span.instrumentation_info is not None:
@@ -205,42 +213,44 @@ def _translate_to_zipkin(self, spans: Sequence[Span]):
             zipkin_spans.append(zipkin_span)
         return zipkin_spans
 
-    def shutdown(self) -> None:
-        pass
-
+    def _extract_tags_from_dict(self, tags_dict):
+        tags = {}
+        if not tags_dict:
+            return tags
+        for attribute_key, attribute_value in tags_dict.items():
+            if isinstance(attribute_value, (int, bool, float)):
+                value = str(attribute_value)
+            elif isinstance(attribute_value, str):
+                value = attribute_value
+            else:
+                logger.warning("Could not serialize tag %s", attribute_key)
+                continue
+
+            if self.max_tag_value_length > 0:
+                value = value[: self.max_tag_value_length]
+            tags[attribute_key] = value
+        return tags
 
-def _extract_tags_from_dict(tags_dict):
-    tags = {}
-    if not tags_dict:
+    def _extract_tags_from_span(self, span: Span):
+        tags = self._extract_tags_from_dict(getattr(span, "attributes", None))
+        if span.resource:
+            tags.update(self._extract_tags_from_dict(span.resource.attributes))
         return tags
-    for attribute_key, attribute_value in tags_dict.items():
-        if isinstance(attribute_value, (int, bool, float)):
-            value = str(attribute_value)
-        elif isinstance(attribute_value, str):
-            value = attribute_value[:128]
-        else:
-            logger.warning("Could not serialize tag %s", attribute_key)
-            continue
-        tags[attribute_key] = value
-    return tags
-
-
-def _extract_tags_from_span(span: Span):
-    tags = _extract_tags_from_dict(getattr(span, "attributes", None))
-    if span.resource:
-        tags.update(_extract_tags_from_dict(span.resource.attributes))
-    return tags
-
-
-def _extract_annotations_from_events(events):
-    return (
-        [
-            {"timestamp": _nsec_to_usec_round(e.timestamp), "value": e.name}
-            for e in events
-        ]
-        if events
-        else None
-    )
+
+    def _extract_annotations_from_events(
+        self, events
+    ):  # pylint: disable=R0201
+        return (
+            [
+                {
+                    "timestamp": _nsec_to_usec_round(e.timestamp),
+                    "value": e.name,
+                }
+                for e in events
+            ]
+            if events
+            else None
+        )
 
 
 def _nsec_to_usec_round(nsec):

exporter/opentelemetry-exporter-zipkin/tests/test_zipkin_exporter.py

@@ -361,3 +361,50 @@ def test_invalid_response(self, mock_post):
         exporter = ZipkinSpanExporter("test-service")
         status = exporter.export(spans)
         self.assertEqual(SpanExportResult.FAILURE, status)
+
+    def test_max_tag_length(self):
+        service_name = "test-service"
+
+        span_context = trace_api.SpanContext(
+            0x0E0C63257DE34C926F9EFCD03927272E,
+            0x04BF92DEEFC58C92,
+            is_remote=False,
+            trace_flags=TraceFlags(TraceFlags.SAMPLED),
+        )
+
+        span = trace.Span(name="test-span", context=span_context,)
+
+        span.start()
+        span.resource = Resource({})
+        # added here to preserve order
+        span.set_attribute("k1", "v" * 500)
+        span.set_attribute("k2", "v" * 50)
+        span.set_status(
+            Status(StatusCanonicalCode.UNKNOWN, "Example description")
+        )
+        span.end()
+
+        exporter = ZipkinSpanExporter(service_name)
+        mock_post = MagicMock()
+        with patch("requests.post", mock_post):
+            mock_post.return_value = MockResponse(200)
+            status = exporter.export([span])
+            self.assertEqual(SpanExportResult.SUCCESS, status)
+
+        _, kwargs = mock_post.call_args  # pylint: disable=E0633
+
+        tags = json.loads(kwargs["data"])[0]["tags"]
+        self.assertEqual(len(tags["k1"]), 128)
+        self.assertEqual(len(tags["k2"]), 50)
+
+        exporter = ZipkinSpanExporter(service_name, max_tag_value_length=2)
+        mock_post = MagicMock()
+        with patch("requests.post", mock_post):
+            mock_post.return_value = MockResponse(200)
+            status = exporter.export([span])
+            self.assertEqual(SpanExportResult.SUCCESS, status)
+
+        _, kwargs = mock_post.call_args  # pylint: disable=E0633
+        tags = json.loads(kwargs["data"])[0]["tags"]
+        self.assertEqual(len(tags["k1"]), 2)
+        self.assertEqual(len(tags["k2"]), 2)