tracer: added noop exporter support

.github/workflows/lint.yml

@@ -43,7 +43,6 @@ jobs:
 
     - uses: actions/setup-python@v5
       with:
-        cache: pip
         python-version: '3.12'
 
     - name: Resolve Karapace version

.github/workflows/tests.yml

@@ -35,7 +35,6 @@ jobs:
     - name: Set up Python ${{ matrix.python-version }}
       uses: actions/setup-python@v5
       with:
-        cache: pip
         python-version: ${{ matrix.python-version }}
 
     - name: Set up Go

container/compose.yml

@@ -86,6 +86,7 @@ services:
       KARAPACE_KAFKA_RETRIABLE_ERRORS_SILENCED: true
       KARAPACE_TAGS__APP: karapace-schema-registry
       KARAPACE_TELEMETRY__OTEL_ENDPOINT_URL: http://opentelemetry-collector:4317
+      KARAPACE_TELEMETRY__OTEL_EXPORTER: OTLP
       KARAPACE_TELEMETRY__RESOURCE_SERVICE_NAME: karapace-schema-registry
       KARAPACE_TELEMETRY__RESOURCE_SERVICE_INSTANCE_ID: sr1
       KARAPACE_TELEMETRY__RESOURCE_TELEMETRY_SDK_NAME: opentelemetry

src/karapace/config.py

@@ -15,6 +15,7 @@
 from pydantic import BaseModel, ImportString
 from pydantic_settings import BaseSettings, SettingsConfigDict
 
+import enum
 import logging
 import os
 import socket
@@ -27,8 +28,15 @@ class KarapaceTags(BaseModel):
     app: str = "Karapace"
 
 
+class KarapaceTelemetryOTelExporter(str, enum.Enum):
+    OTLP = "OTLP"
+    CONSOLE = "CONSOLE"
+    NOOP = "NOOP"
+
+
 class KarapaceTelemetry(BaseModel):
     otel_endpoint_url: str | None = None
+    otel_exporter: KarapaceTelemetryOTelExporter = KarapaceTelemetryOTelExporter.NOOP
     resource_service_name: str = "karapace"
     resource_service_instance_id: str = "karapace"
     resource_telemetry_sdk_name: str = "opentelemetry"

src/schema_registry/telemetry/tracer.py

@@ -3,14 +3,22 @@
 See LICENSE for details
 """
 
-from collections.abc import Callable
+from collections.abc import Callable, Sequence
 from dependency_injector.wiring import inject, Provide
 from fastapi import Request, Response
-from karapace.config import Config
+from karapace.config import Config, KarapaceTelemetryOTelExporter
 from karapace.container import KarapaceContainer
 from opentelemetry import trace
 from opentelemetry.exporter.otlp.proto.grpc.trace_exporter import OTLPSpanExporter
-from opentelemetry.sdk.trace.export import BatchSpanProcessor, ConsoleSpanExporter, SimpleSpanProcessor, SpanProcessor
+from opentelemetry.sdk.trace import ReadableSpan
+from opentelemetry.sdk.trace.export import (
+    BatchSpanProcessor,
+    ConsoleSpanExporter,
+    SimpleSpanProcessor,
+    SpanExporter,
+    SpanExportResult,
+    SpanProcessor,
+)
 from opentelemetry.semconv.attributes import (
     client_attributes as C,
     http_attributes as H,
@@ -22,19 +30,41 @@
 import inspect
 
 
+class NOOPSpanExporter(SpanExporter):
+    """Implementation of :class:`SpanExporter` that does nothing.
+
+    This class is intended to be used when tracing exporting to an OTel backend is disabled
+    and the ConsoleExporter is too verbose to be used.
+    """
+
+    def export(self, _: Sequence[ReadableSpan]) -> SpanExportResult:
+        return SpanExportResult.SUCCESS
+
+    def force_flush(self, _: int = 0) -> bool:
+        return False
+
+
 class Tracer:
     @staticmethod
     @inject
     def get_tracer(config: Config = Provide[KarapaceContainer.config]) -> trace.Tracer:
         return trace.get_tracer(f"{config.tags.app}.tracer")
 
+    @staticmethod
+    def get_span_exporter(config: Config) -> SpanExporter:
+        match config.telemetry.otel_exporter:
+            case KarapaceTelemetryOTelExporter.NOOP:
+                return NOOPSpanExporter()
+            case KarapaceTelemetryOTelExporter.CONSOLE:
+                return ConsoleSpanExporter()
+            case KarapaceTelemetryOTelExporter.OTLP:
+                return OTLPSpanExporter(endpoint=config.telemetry.otel_endpoint_url)
+
     @staticmethod
     @inject
     def get_span_processor(config: Config = Provide[KarapaceContainer.config]) -> SpanProcessor:
-        if config.telemetry.otel_endpoint_url:
-            otlp_span_exporter = OTLPSpanExporter(endpoint=config.telemetry.otel_endpoint_url)
-            return BatchSpanProcessor(otlp_span_exporter)
-        return SimpleSpanProcessor(ConsoleSpanExporter())
+        processor = BatchSpanProcessor if config.telemetry.otel_endpoint_url else SimpleSpanProcessor
+        return processor(Tracer.get_span_exporter(config=config))
 
     @staticmethod
     def get_name_from_caller() -> str:

tests/unit/schema_registry/telemetry/test_tracer.py

@@ -8,9 +8,9 @@
 from fastapi import Request, Response
 from karapace.config import KarapaceTelemetry
 from karapace.container import KarapaceContainer
-from opentelemetry.sdk.trace.export import SpanProcessor
+from opentelemetry.sdk.trace.export import ConsoleSpanExporter, SpanExporter, SpanProcessor
 from opentelemetry.trace.span import Span
-from schema_registry.telemetry.tracer import Tracer
+from schema_registry.telemetry.tracer import NOOPSpanExporter, Tracer
 from unittest.mock import call, MagicMock, patch
 
 
@@ -35,9 +35,55 @@ def test_function(self):
     assert Test().test_function() == "Test.test_function()"
 
 
+def test_get_span_exporter_noop(karapace_container: KarapaceContainer) -> None:
+    config = karapace_container.config().set_config_defaults(
+        new_config={
+            "telemetry": KarapaceTelemetry(
+                otel_endpoint_url="http://otel:4317",
+                otel_exporter="NOOP",
+            )
+        }
+    )
+    exporter: SpanExporter = Tracer.get_span_exporter(config=config)
+    assert isinstance(exporter, NOOPSpanExporter)
+
+
+def test_get_span_exporter_console(karapace_container: KarapaceContainer) -> None:
+    config = karapace_container.config().set_config_defaults(
+        new_config={
+            "telemetry": KarapaceTelemetry(
+                otel_endpoint_url="http://otel:4317",
+                otel_exporter="CONSOLE",
+            )
+        }
+    )
+    exporter: SpanExporter = Tracer.get_span_exporter(config=config)
+    assert isinstance(exporter, ConsoleSpanExporter)
+
+
+def test_get_span_exporter_otlp(karapace_container: KarapaceContainer) -> None:
+    config = karapace_container.config().set_config_defaults(
+        new_config={
+            "telemetry": KarapaceTelemetry(
+                otel_endpoint_url="http://otel:4317",
+                otel_exporter="OTLP",
+            )
+        }
+    )
+    with patch("schema_registry.telemetry.tracer.OTLPSpanExporter") as mock_otlp_exporter:
+        exporter: SpanExporter = Tracer.get_span_exporter(config=config)
+        mock_otlp_exporter.assert_called_once_with(endpoint="http://otel:4317")
+        assert exporter is mock_otlp_exporter.return_value
+
+
 def test_get_span_processor_with_otel_endpoint(karapace_container: KarapaceContainer) -> None:
     config = karapace_container.config().set_config_defaults(
-        new_config={"telemetry": KarapaceTelemetry(otel_endpoint_url="http://otel:4317")}
+        new_config={
+            "telemetry": KarapaceTelemetry(
+                otel_endpoint_url="http://otel:4317",
+                otel_exporter="OTLP",
+            )
+        }
     )
     with (
         patch("schema_registry.telemetry.tracer.OTLPSpanExporter") as mock_otlp_exporter,
@@ -54,11 +100,11 @@ def test_get_span_processor_without_otel_endpoint(karapace_container: KarapaceCo
         new_config={"telemetry": KarapaceTelemetry(otel_endpoint_url=None)}
     )
     with (
-        patch("schema_registry.telemetry.tracer.ConsoleSpanExporter") as mock_console_exporter,
         patch("schema_registry.telemetry.tracer.SimpleSpanProcessor") as mock_simple_span_processor,
+        patch("schema_registry.telemetry.tracer.NOOPSpanExporter") as mock_noop_exporter,
     ):
         processor: SpanProcessor = Tracer.get_span_processor(config=config)
-        mock_simple_span_processor.assert_called_once_with(mock_console_exporter.return_value)
+        mock_simple_span_processor.assert_called_once_with(mock_noop_exporter.return_value)
         assert processor is mock_simple_span_processor.return_value