feat(metrics): Add trace metrics behind an experiments flag (#4898)

### Summary
Similar to getsentry/sentry-javascript#17883,
this allows the py sdk to send in new trace metric protocol items,
although this code is experimental since the schema may still change.
Most of this code has been copied from logs (eg. log batcher -> metrics
batcher) in order to dogfood, once we're more sure of our approach we
can refactor.

Closes LOGS-367

---------

Co-authored-by: Ivana Kellyer <[email protected]>

Author: k-fish

sentry_sdk/_metrics.py

@@ -0,0 +1,81 @@
+"""
+NOTE: This file contains experimental code that may be changed or removed at any
+time without prior notice.
+"""
+
+import time
+from typing import Any, Optional, TYPE_CHECKING, Union
+
+import sentry_sdk
+from sentry_sdk.utils import safe_repr
+
+if TYPE_CHECKING:
+    from sentry_sdk._types import Metric, MetricType
+
+
+def _capture_metric(
+    name,  # type: str
+    metric_type,  # type: MetricType
+    value,  # type: float
+    unit=None,  # type: Optional[str]
+    attributes=None,  # type: Optional[dict[str, Any]]
+):
+    # type: (...) -> None
+    client = sentry_sdk.get_client()
+
+    attrs = {}  # type: dict[str, Union[str, bool, float, int]]
+    if attributes:
+        for k, v in attributes.items():
+            attrs[k] = (
+                v
+                if (
+                    isinstance(v, str)
+                    or isinstance(v, int)
+                    or isinstance(v, bool)
+                    or isinstance(v, float)
+                )
+                else safe_repr(v)
+            )
+
+    metric = {
+        "timestamp": time.time(),
+        "trace_id": None,
+        "span_id": None,
+        "name": name,
+        "type": metric_type,
+        "value": float(value),
+        "unit": unit,
+        "attributes": attrs,
+    }  # type: Metric
+
+    client._capture_metric(metric)
+
+
+def count(
+    name,  # type: str
+    value,  # type: float
+    unit=None,  # type: Optional[str]
+    attributes=None,  # type: Optional[dict[str, Any]]
+):
+    # type: (...) -> None
+    _capture_metric(name, "counter", value, unit, attributes)
+
+
+def gauge(
+    name,  # type: str
+    value,  # type: float
+    unit=None,  # type: Optional[str]
+    attributes=None,  # type: Optional[dict[str, Any]]
+):
+    # type: (...) -> None
+    _capture_metric(name, "gauge", value, unit, attributes)
+
+
+def distribution(
+    name,  # type: str
+    value,  # type: float
+    unit=None,  # type: Optional[str]
+    attributes=None,  # type: Optional[dict[str, Any]]
+):
+    # type: (...) -> None
+    _capture_metric(name, "distribution", value, unit, attributes)

sentry_sdk/_metrics_batcher.py

@@ -0,0 +1,156 @@
+import os
+import random
+import threading
+from datetime import datetime, timezone
+from typing import Optional, List, Callable, TYPE_CHECKING, Any, Union
+
+from sentry_sdk.utils import format_timestamp, safe_repr
+from sentry_sdk.envelope import Envelope, Item, PayloadRef
+
+if TYPE_CHECKING:
+    from sentry_sdk._types import Metric
+
+
+class MetricsBatcher:
+    MAX_METRICS_BEFORE_FLUSH = 100
+    FLUSH_WAIT_TIME = 5.0
+
+    def __init__(
+        self,
+        capture_func,  # type: Callable[[Envelope], None]
+    ):
+        # type: (...) -> None
+        self._metric_buffer = []  # type: List[Metric]
+        self._capture_func = capture_func
+        self._running = True
+        self._lock = threading.Lock()
+
+        self._flush_event = threading.Event()  # type: threading.Event
+
+        self._flusher = None  # type: Optional[threading.Thread]
+        self._flusher_pid = None  # type: Optional[int]
+
+    def _ensure_thread(self):
+        # type: (...) -> bool
+        if not self._running:
+            return False
+
+        pid = os.getpid()
+        if self._flusher_pid == pid:
+            return True
+
+        with self._lock:
+            if self._flusher_pid == pid:
+                return True
+
+            self._flusher_pid = pid
+
+            self._flusher = threading.Thread(target=self._flush_loop)
+            self._flusher.daemon = True
+
+            try:
+                self._flusher.start()
+            except RuntimeError:
+                self._running = False
+                return False
+
+        return True
+
+    def _flush_loop(self):
+        # type: (...) -> None
+        while self._running:
+            self._flush_event.wait(self.FLUSH_WAIT_TIME + random.random())
+            self._flush_event.clear()
+            self._flush()
+
+    def add(
+        self,
+        metric,  # type: Metric
+    ):
+        # type: (...) -> None
+        if not self._ensure_thread() or self._flusher is None:
+            return None
+
+        with self._lock:
+            self._metric_buffer.append(metric)
+            if len(self._metric_buffer) >= self.MAX_METRICS_BEFORE_FLUSH:
+                self._flush_event.set()
+
+    def kill(self):
+        # type: (...) -> None
+        if self._flusher is None:
+            return
+
+        self._running = False
+        self._flush_event.set()
+        self._flusher = None
+
+    def flush(self):
+        # type: (...) -> None
+        self._flush()
+
+    @staticmethod
+    def _metric_to_transport_format(metric):
+        # type: (Metric) -> Any
+        def format_attribute(val):
+            # type: (Union[int, float, str, bool]) -> Any
+            if isinstance(val, bool):
+                return {"value": val, "type": "boolean"}
+            if isinstance(val, int):
+                return {"value": val, "type": "integer"}
+            if isinstance(val, float):
+                return {"value": val, "type": "double"}
+            if isinstance(val, str):
+                return {"value": val, "type": "string"}
+            return {"value": safe_repr(val), "type": "string"}
+
+        res = {
+            "timestamp": metric["timestamp"],
+            "trace_id": metric["trace_id"],
+            "name": metric["name"],
+            "type": metric["type"],
+            "value": metric["value"],
+            "attributes": {
+                k: format_attribute(v) for (k, v) in metric["attributes"].items()
+            },
+        }
+
+        if metric.get("span_id") is not None:
+            res["span_id"] = metric["span_id"]
+
+        if metric.get("unit") is not None:
+            res["unit"] = metric["unit"]
+
+        return res
+
+    def _flush(self):
+        # type: (...) -> Optional[Envelope]
+
+        envelope = Envelope(
+            headers={"sent_at": format_timestamp(datetime.now(timezone.utc))}
+        )
+        with self._lock:
+            if len(self._metric_buffer) == 0:
+                return None
+
+            envelope.add_item(
+                Item(
+                    type="trace_metric",
+                    content_type="application/vnd.sentry.items.trace-metric+json",
+                    headers={
+                        "item_count": len(self._metric_buffer),
+                    },
+                    payload=PayloadRef(
+                        json={
+                            "items": [
+                                self._metric_to_transport_format(metric)
+                                for metric in self._metric_buffer
+                            ]
+                        }
+                    ),
+                )
+            )
+            self._metric_buffer.clear()
+
+        self._capture_func(envelope)
+        return envelope

sentry_sdk/_types.py

@@ -234,6 +234,32 @@ class SDKInfo(TypedDict):
         },
     )
 
+    MetricType = Literal["counter", "gauge", "distribution"]
+
+    MetricAttributeValue = TypedDict(
+        "MetricAttributeValue",
+        {
+            "value": Union[str, bool, float, int],
+            "type": Literal["string", "boolean", "double", "integer"],
+        },
+    )
+
+    Metric = TypedDict(
+        "Metric",
+        {
+            "timestamp": float,
+            "trace_id": Optional[str],
+            "span_id": Optional[str],
+            "name": str,
+            "type": MetricType,
+            "value": float,
+            "unit": Optional[str],
+            "attributes": dict[str, str | bool | float | int],
+        },
+    )
+
+    MetricProcessor = Callable[[Metric, Hint], Optional[Metric]]
+
     # TODO: Make a proper type definition for this (PRs welcome!)
     Breadcrumb = Dict[str, Any]
 
@@ -268,6 +294,7 @@ class SDKInfo(TypedDict):
         "monitor",
         "span",
         "log_item",
+        "trace_metric",
     ]
     SessionStatus = Literal["ok", "exited", "crashed", "abnormal"]