Make opentracing an optional dependency (faust[opentracing])

.coveragerc

@@ -33,6 +33,12 @@ omit =
     # not needed
     */faust/utils/iso8601.py
     */faust/utils/tracing.py
+    # opentracing fallback stub: only used when opentracing is NOT installed,
+    # which the CI test env is not (it installs faust[opentracing]).
+    */faust/utils/_opentracing.py
+    # opentracing distributed-tracing sensor: optional, requires opentracing +
+    # a live tracer to exercise; not covered by the CI test suite.
+    */faust/sensors/distributed_tracing.py
     */faust/types/*
     */faust/__main__.py
 

faust/app/base.py

@@ -42,7 +42,10 @@
     no_type_check,
 )
 
-import opentracing
+try:
+    import opentracing
+except ImportError:  # pragma: no cover
+    from faust.utils import _opentracing as opentracing  # type: ignore
 from mode import Seconds, Service, ServiceT, SupervisorStrategyT, want_seconds
 from mode.utils.aiter import aiter
 from mode.utils.collections import force_mapping

faust/sensors/distributed_tracing.py

@@ -3,11 +3,16 @@
 from typing import Any, Dict
 
 import aiohttp
-import opentracing
 from mode import get_logger
 from mode.utils.compat import want_str
-from opentracing import Format
-from opentracing.ext import tags
+
+try:
+    import opentracing
+    from opentracing import Format
+    from opentracing.ext import tags
+except ImportError:  # pragma: no cover
+    from faust.utils import _opentracing as opentracing  # type: ignore
+    from faust.utils._opentracing import Format, tags
 
 from faust import App, EventT, Sensor, StreamT
 from faust.types import TP, Message, PendingMessage, ProducerT, RecordMetadata

faust/tables/recovery.py

@@ -20,7 +20,10 @@
     cast,
 )
 
-import opentracing
+try:
+    import opentracing
+except ImportError:  # pragma: no cover
+    from faust.utils import _opentracing as opentracing  # type: ignore
 from aiokafka.errors import IllegalStateError
 from mode import Service, get_logger
 from mode.services import WaitArgT

faust/transport/drivers/aiokafka.py

@@ -26,7 +26,6 @@
 
 import aiokafka
 import aiokafka.abc
-import opentracing
 from aiokafka import TopicPartition
 from aiokafka.consumer.group_coordinator import OffsetCommitRequest
 from aiokafka.coordinator.assignors.roundrobin import RoundRobinPartitionAssignor
@@ -51,10 +50,16 @@
 from mode.utils.futures import StampedeWrapper
 from mode.utils.objects import cached_property
 from mode.utils.times import Seconds, humanize_seconds_ago, want_seconds
-from opentracing.ext import tags
 from packaging.version import Version
 from yarl import URL
 
+try:
+    import opentracing
+    from opentracing.ext import tags
+except ImportError:  # pragma: no cover
+    from faust.utils import _opentracing as opentracing  # type: ignore
+    from faust.utils._opentracing import tags
+
 from faust.auth import (
     GSSAPICredentials,
     OAuthCredentials,

faust/types/app.py

@@ -23,7 +23,10 @@
     no_type_check,
 )
 
-import opentracing
+try:
+    import opentracing
+except ImportError:  # pragma: no cover
+    from faust.utils import _opentracing as opentracing  # type: ignore
 from mode import Seconds, ServiceT, Signal, SupervisorStrategyT, SyncSignal
 from mode.utils.futures import stampede
 from mode.utils.objects import cached_property

faust/utils/_opentracing.py

@@ -0,0 +1,102 @@
+"""No-op stand-in for :pypi:`opentracing`.
+
+OpenTracing is an optional dependency (``faust[opentracing]``). When it is not
+installed, the tracing modules fall back to this module so that Faust still
+imports and runs -- tracing simply becomes a no-op. Distributed tracing only
+does real work when an ``app.tracer`` is configured (or the ``TracingSensor``
+is used), which requires the real ``opentracing`` package to be installed.
+
+This intentionally implements only the small surface Faust touches.
+"""
+
+from typing import Any
+
+
+class Span:
+    """A span that does nothing."""
+
+    operation_name: str = ""
+
+    def __init__(self, *args: Any, **kwargs: Any) -> None:
+        self.context = _SpanContext()
+        self.tracer: Any = None
+
+    def __enter__(self) -> "Span":
+        return self
+
+    def __exit__(self, *exc_info: Any) -> bool:
+        return False
+
+    def finish(self, *args: Any, **kwargs: Any) -> None: ...
+
+    def set_tag(self, *args: Any, **kwargs: Any) -> "Span":
+        return self
+
+    def set_operation_name(self, *args: Any, **kwargs: Any) -> "Span":
+        return self
+
+    def log_kv(self, *args: Any, **kwargs: Any) -> "Span":
+        return self
+
+    def set_baggage_item(self, *args: Any, **kwargs: Any) -> "Span":
+        return self
+
+    def get_baggage_item(self, *args: Any, **kwargs: Any) -> Any:
+        return None
+
+
+class _SpanContext:
+    trace_id: Any = None
+    span_id: Any = None
+
+
+class Tracer:
+    """A tracer that produces only no-op spans."""
+
+    def __init__(self, *args: Any, **kwargs: Any) -> None:
+        self._noop_span = Span()
+
+    def start_span(self, *args: Any, **kwargs: Any) -> Span:
+        return Span()
+
+    def start_active_span(self, *args: Any, **kwargs: Any) -> Span:
+        return Span()
+
+    def extract(self, *args: Any, **kwargs: Any) -> Any:
+        return None
+
+    def inject(self, *args: Any, **kwargs: Any) -> None: ...
+
+
+#: Module-level global tracer, mirroring ``opentracing.tracer``.
+tracer = Tracer()
+
+
+def follows_from(*args: Any, **kwargs: Any) -> Any:
+    return None
+
+
+def child_of(*args: Any, **kwargs: Any) -> Any:
+    return None
+
+
+def start_child_span(*args: Any, **kwargs: Any) -> Span:
+    return Span()
+
+
+class Format:
+    """Mirror of ``opentracing.Format`` carrier formats."""
+
+    TEXT_MAP = "text_map"
+    HTTP_HEADERS = "http_headers"
+    BINARY = "binary"
+
+
+class tags:
+    """Mirror of the ``opentracing.ext.tags`` constants Faust references."""
+
+    ERROR = "error"
+    SAMPLING_PRIORITY = "sampling.priority"
+    SPAN_KIND = "span.kind"
+    COMPONENT = "component"
+    MESSAGE_BUS_DESTINATION = "message_bus.destination"

faust/utils/tracing.py

@@ -7,7 +7,10 @@
 from functools import wraps
 from typing import Any, Callable, Optional, Tuple
 
-import opentracing
+try:
+    import opentracing
+except ImportError:  # pragma: no cover
+    from faust.utils import _opentracing as opentracing  # type: ignore
 from mode import shortlabel
 
 __all__ = [

requirements/extras/opentracing.txt

@@ -0,0 +1 @@
+opentracing>=1.3.0,<=2.4.0

requirements/requirements.txt

@@ -3,7 +3,6 @@ aiohttp_cors>=0.7,<2.0
 aiokafka>=0.10.0
 click>=6.7,<8.2
 mode-streaming>=0.4.0
-opentracing>=1.3.0,<=2.4.0
 terminaltables>=3.1,<4.0
 yarl>=1.0,<2.0
 croniter>=0.3.16

requirements/test.txt

@@ -28,6 +28,7 @@ wheel
 intervaltree
 -r requirements.txt
 -r extras/datadog.txt
+-r extras/opentracing.txt
 -r extras/redis.txt
 -r extras/statsd.txt
 -r extras/yaml.txt

setup.py

@@ -30,6 +30,7 @@
     "datadog",
     "debug",
     "fast",
+    "opentracing",
     "orjson",
     "prometheus",
     "redis",