Adding distributed tracing feature (#376)

* Adding distributed tracing

* fix linting

* Revert "fix linting"

This reverts commit 315bc65.

* Fix linting

faust/sensors/distributed_tracing.py

@@ -0,0 +1,164 @@
+import traceback
+from functools import cached_property
+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
+
+from faust import App, EventT, Sensor, StreamT
+from faust.types import TP, Message, PendingMessage, ProducerT, RecordMetadata
+from faust.types.core import OpenHeadersArg, merge_headers
+from faust.utils.tracing import current_span, set_current_span
+
+logger = get_logger(__name__)
+
+
+class TracingSensor(Sensor):
+    aiohttp_sessions: Dict[str, aiohttp.ClientSession] = None
+
+    @cached_property
+    def app_tracer(self) -> opentracing.Tracer:
+        return opentracing.tracer
+
+    async def stop(self) -> None:
+        if self.aiohttp_sessions:
+            for session in self.aiohttp_sessions.values():
+                await session.close()
+        await super().stop()
+
+    @cached_property
+    def kafka_tracer(self) -> opentracing.Tracer:
+        return opentracing.tracer
+
+    # Message received by a consumer.
+    def on_message_in(self, tp: TP, offset: int, message: Message) -> None:
+        carrier_headers = {want_str(k): want_str(v) for k, v in message.headers}
+
+        if carrier_headers:
+            parent_context = self.app_tracer.extract(
+                format=Format.TEXT_MAP, carrier=carrier_headers
+            )
+            span = self.app_tracer.start_span(
+                operation_name=f"consume-from-{message.topic}",
+                references=opentracing.follows_from(parent_context),
+            )
+        else:
+            span = self.app_tracer.start_span(
+                operation_name=f"consume-from-{message.topic}"
+            )
+        set_current_span(span)
+        span.set_tag("kafka-topic", tp.topic)
+        span.set_tag("kafka-partition", tp.partition)
+        span.set_tag("kafka-key", message.key)
+        span.__enter__()
+        message.span = span  # type: ignore
+
+    # Message sent to a stream as an event.
+    def on_stream_event_in(
+        self, tp: TP, offset: int, stream: StreamT, event: EventT
+    ) -> None:
+        stream_meta = getattr(event.message, "stream_meta", None)
+        if stream_meta is None:
+            stream_meta = event.message.stream_meta = {}  # type: ignore
+        parent_span = event.message.span  # type: ignore
+        if parent_span:
+            stream_span = opentracing.start_child_span(
+                parent_span, f"job-{event.message.topic}"
+            )
+            stream_span.set_tag("stream-concurrency-index", stream.concurrency_index)
+            stream_span.set_tag("stream-prefix", stream.prefix)
+            spans = stream_meta.get("stream_spans")
+            if spans is None:
+                spans = stream_meta["stream_spans"] = {}
+            spans[stream] = stream_span
+            stream_span.__enter__()
+
+    # Event was acknowledged by stream.
+    def on_stream_event_out(
+        self, tp: TP, offset: int, stream: StreamT, event: EventT, state: Dict = None
+    ) -> None:
+        stream_meta = getattr(event.message, "stream_meta", None)
+        if stream_meta is None:
+            stream_meta = event.message.stream_meta = {}  # type: ignore
+        stream_spans = stream_meta.get("stream_spans")
+        if stream_spans:
+            span = stream_spans.pop(stream, None)
+            if span is not None:
+                span.finish()
+
+    # All streams finished processing message.
+    def on_message_out(self, tp: TP, offset: int, message: Message) -> None:
+        span = message.span  # type: ignore
+        if span:
+            span.finish()
+
+    # About to send a message.
+    def on_send_initiated(
+        self,
+        producer: ProducerT,
+        topic: str,
+        message: PendingMessage,
+        keysize: int,
+        valsize: int,
+    ) -> Any:
+        parent_span = current_span()
+        if parent_span:
+            span = opentracing.start_child_span(parent_span, f"produce-to-{topic}")
+            header_map = dict(message.headers) if message.headers else {}
+            span.set_tag("kafka-headers", header_map)
+            self.trace_inject_headers(span, message.headers)
+            span.__enter__()
+            return {"span": span}
+        return {"span": None}
+
+    # Message successfully sent.
+    def on_send_completed(
+        self, producer: ProducerT, state: Any, metadata: RecordMetadata
+    ) -> None:
+        span = state.get("span")
+        if span is not None:
+            span.set_tag("kafka-topic", metadata.topic)
+            span.set_tag("kafka-partition", metadata.partition)
+            span.set_tag("kafka-offset", metadata.offset)
+            span.finish()
+
+    # Error while sending message.
+    def on_send_error(
+        self, producer: ProducerT, exc: BaseException, state: Any
+    ) -> None:
+        span = state.get("span")
+        if span is not None:
+            span.set_tag(tags.ERROR, "true")
+            span.log_kv(
+                {
+                    "python.exception.type": type(exc),
+                    "python.exception.val": exc,
+                    "python.exception.tb": traceback.format_stack(),
+                }
+            )
+            span.finish(exception=exc)
+
+    def trace_inject_headers(
+        self, span: opentracing.Span, headers: OpenHeadersArg
+    ) -> Any:
+        try:
+            if self.app_tracer is not None:
+                if span is not None:
+                    carrier: Dict = {}
+                    self.app_tracer.inject(
+                        span_context=span.context,
+                        format=opentracing.Format.TEXT_MAP,
+                        carrier=carrier,
+                    )
+                    merge_headers(headers, carrier)
+            return headers
+        except Exception as ex:
+            logger.warning(f"Exception in trace_inject_headers {ex} ")
+            return None
+
+    def on_threaded_producer_buffer_processed(self, app: App, size: int) -> None:
+        pass