tracing_utils.py

import contextlib
import inspect
import os
import re
import sys
from collections.abc import Mapping
from datetime import timedelta
from decimal import ROUND_DOWN, Context, Decimal
from functools import wraps
from random import Random
from urllib.parse import quote, unquote
import uuid

import sentry_sdk
from sentry_sdk.consts import OP, SPANDATA
from sentry_sdk.utils import (
    capture_internal_exceptions,
    filename_for_module,
    Dsn,
    logger,
    match_regex_list,
    qualname_from_function,
    to_string,
    try_convert,
    is_sentry_url,
    _is_external_source,
    _is_in_project_root,
    _module_in_list,
)

from typing import TYPE_CHECKING

if TYPE_CHECKING:
    from typing import Any
    from typing import Dict
    from typing import Generator
    from typing import Optional
    from typing import Union

    from types import FrameType


SENTRY_TRACE_REGEX = re.compile(
    "^[ \t]*"  # whitespace
    "([0-9a-f]{32})?"  # trace_id
    "-?([0-9a-f]{16})?"  # span_id
    "-?([01])?"  # sampled
    "[ \t]*$"  # whitespace
)

W3C_TRACE_REGEX = re.compile(
    "^[ \t]*"  # whitespace
    "[0-9]{2}?"  # version
    "-?([0-9a-f]{32})?"  # trace_id
    "-?([0-9a-f]{16})?"  # span_id
    "-?([0-9]{2})?"  # trace-flags
    "[ \t]*$"  # whitespace
)

# This is a normal base64 regex, modified to reflect that fact that we strip the
# trailing = or == off
base64_stripped = (
    # any of the characters in the base64 "alphabet", in multiples of 4
    "([a-zA-Z0-9+/]{4})*"
    # either nothing or 2 or 3 base64-alphabet characters (see
    # https://en.wikipedia.org/wiki/Base64#Decoding_Base64_without_padding for
    # why there's never only 1 extra character)
    "([a-zA-Z0-9+/]{2,3})?"
)


class EnvironHeaders(Mapping):  # type: ignore
    def __init__(
        self,
        environ,  # type: Mapping[str, str]
        prefix="HTTP_",  # type: str
    ):
        # type: (...) -> None
        self.environ = environ
        self.prefix = prefix

    def __getitem__(self, key):
        # type: (str) -> Optional[Any]
        return self.environ[self.prefix + key.replace("-", "_").upper()]

    def __len__(self):
        # type: () -> int
        return sum(1 for _ in iter(self))

    def __iter__(self):
        # type: () -> Generator[str, None, None]
        for k in self.environ:
            if not isinstance(k, str):
                continue

            k = k.replace("-", "_").upper()
            if not k.startswith(self.prefix):
                continue

            yield k[len(self.prefix) :]


def has_tracing_enabled(options):
    # type: (Optional[Dict[str, Any]]) -> bool
    """
    Returns True if either traces_sample_rate or traces_sampler is
    defined and enable_tracing is set and not false.
    """
    if options is None:
        return False

    return bool(
        options.get("enable_tracing") is not False
        and (
            options.get("traces_sample_rate") is not None
            or options.get("traces_sampler") is not None
        )
    )


@contextlib.contextmanager
def record_sql_queries(
    cursor,  # type: Any
    query,  # type: Any
    params_list,  # type:  Any
    paramstyle,  # type: Optional[str]
    executemany,  # type: bool
    record_cursor_repr=False,  # type: bool
    span_origin="manual",  # type: str
):
    # type: (...) -> Generator[sentry_sdk.tracing.Span, None, None]

    # TODO: Bring back capturing of params by default
    if sentry_sdk.get_client().options["_experiments"].get("record_sql_params", False):
        if not params_list or params_list == [None]:
            params_list = None

        if paramstyle == "pyformat":
            paramstyle = "format"
    else:
        params_list = None
        paramstyle = None

    query = _format_sql(cursor, query)

    data = {}
    if params_list is not None:
        data["db.params"] = params_list
    if paramstyle is not None:
        data["db.paramstyle"] = paramstyle
    if executemany:
        data["db.executemany"] = True
    if record_cursor_repr and cursor is not None:
        data["db.cursor"] = cursor

    with capture_internal_exceptions():
        sentry_sdk.add_breadcrumb(message=query, category="query", data=data)

    with sentry_sdk.start_span(
        op=OP.DB,
        name=query,
        origin=span_origin,
    ) as span:
        for k, v in data.items():
            span.set_data(k, v)
        yield span


def maybe_create_breadcrumbs_from_span(scope, span):
    # type: (sentry_sdk.Scope, sentry_sdk.tracing.Span) -> None
    if span.op == OP.DB_REDIS:
        scope.add_breadcrumb(
            message=span.description, type="redis", category="redis", data=span._tags
        )

    elif span.op == OP.HTTP_CLIENT:
        level = None
        status_code = span._data.get(SPANDATA.HTTP_STATUS_CODE)
        if status_code:
            if 500 <= status_code <= 599:
                level = "error"
            elif 400 <= status_code <= 499:
                level = "warning"

        if level:
            scope.add_breadcrumb(
                type="http", category="httplib", data=span._data, level=level
            )
        else:
            scope.add_breadcrumb(type="http", category="httplib", data=span._data)

    elif span.op == "subprocess":
        scope.add_breadcrumb(
            type="subprocess",
            category="subprocess",
            message=span.description,
            data=span._data,
        )


def _get_frame_module_abs_path(frame):
    # type: (FrameType) -> Optional[str]
    try:
        return frame.f_code.co_filename
    except Exception:
        return None


def _should_be_included(
    is_sentry_sdk_frame,  # type: bool
    namespace,  # type: Optional[str]
    in_app_include,  # type: Optional[list[str]]
    in_app_exclude,  # type: Optional[list[str]]
    abs_path,  # type: Optional[str]
    project_root,  # type: Optional[str]
):
    # type: (...) -> bool
    # in_app_include takes precedence over in_app_exclude
    should_be_included = _module_in_list(namespace, in_app_include)
    should_be_excluded = _is_external_source(abs_path) or _module_in_list(
        namespace, in_app_exclude
    )
    return not is_sentry_sdk_frame and (
        should_be_included
        or (_is_in_project_root(abs_path, project_root) and not should_be_excluded)
    )


def add_query_source(span):
    # type: (sentry_sdk.tracing.Span) -> None
    """
    Adds OTel compatible source code information to the span
    """
    client = sentry_sdk.get_client()
    if not client.is_active():
        return

    if span.timestamp is None or span.start_timestamp is None:
        return

    should_add_query_source = client.options.get("enable_db_query_source", True)
    if not should_add_query_source:
        return

    duration = span.timestamp - span.start_timestamp
    threshold = client.options.get("db_query_source_threshold_ms", 0)
    slow_query = duration / timedelta(milliseconds=1) > threshold

    if not slow_query:
        return

    project_root = client.options["project_root"]
    in_app_include = client.options.get("in_app_include")
    in_app_exclude = client.options.get("in_app_exclude")

    # Find the correct frame
    frame = sys._getframe()  # type: Union[FrameType, None]
    while frame is not None:
        abs_path = _get_frame_module_abs_path(frame)

        try:
            namespace = frame.f_globals.get("__name__")  # type: Optional[str]
        except Exception:
            namespace = None

        is_sentry_sdk_frame = namespace is not None and namespace.startswith(
            "sentry_sdk."
        )

        should_be_included = _should_be_included(
            is_sentry_sdk_frame=is_sentry_sdk_frame,
            namespace=namespace,
            in_app_include=in_app_include,
            in_app_exclude=in_app_exclude,
            abs_path=abs_path,
            project_root=project_root,
        )
        if should_be_included:
            break

        frame = frame.f_back
    else:
        frame = None

    # Set the data
    if frame is not None:
        try:
            lineno = frame.f_lineno
        except Exception:
            lineno = None
        if lineno is not None:
            span.set_data(SPANDATA.CODE_LINENO, frame.f_lineno)

        try:
            namespace = frame.f_globals.get("__name__")
        except Exception:
            namespace = None
        if namespace is not None:
            span.set_data(SPANDATA.CODE_NAMESPACE, namespace)

        filepath = _get_frame_module_abs_path(frame)
        if filepath is not None:
            if namespace is not None:
                in_app_path = filename_for_module(namespace, filepath)
            elif project_root is not None and filepath.startswith(project_root):
                in_app_path = filepath.replace(project_root, "").lstrip(os.sep)
            else:
                in_app_path = filepath
            span.set_data(SPANDATA.CODE_FILEPATH, in_app_path)

        try:
            code_function = frame.f_code.co_name
        except Exception:
            code_function = None

        if code_function is not None:
            span.set_data(SPANDATA.CODE_FUNCTION, frame.f_code.co_name)


def extract_sentrytrace_data(header):
    # type: (Optional[str]) -> Optional[Dict[str, Union[str, bool, None]]]
    """
    Given a `sentry-trace` header string, return a dictionary of data.
    """
    if not header:
        return None

    if header.startswith("00-") and header.endswith("-00"):
        header = header[3:-3]

    match = SENTRY_TRACE_REGEX.match(header)
    if not match:
        return None

    trace_id, parent_span_id, sampled_str = match.groups()
    parent_sampled = None

    if trace_id:
        trace_id = "{:032x}".format(int(trace_id, 16))
    if parent_span_id:
        parent_span_id = "{:016x}".format(int(parent_span_id, 16))
    if sampled_str:
        parent_sampled = sampled_str != "0"

    return {
        "trace_id": trace_id,
        "parent_span_id": parent_span_id,
        "parent_sampled": parent_sampled,
    }


def extract_w3c_traceparent_data(header):
    # type: (Optional[str]) -> Optional[Dict[str, Union[str, bool, None]]]
    """
    Given a `traceparent` header string, return a dictionary of data.
    """
    if not header or not header.startswith("00-"):
        return None

    match = W3C_TRACE_REGEX.match(header)
    if not match:
        return None

    trace_id, parent_span_id, trace_flags = match.groups()
    parent_sampled = None

    if trace_id:
        trace_id = "{:032x}".format(int(trace_id, 16))
    if parent_span_id:
        parent_span_id = "{:016x}".format(int(parent_span_id, 16))
    if trace_flags:
        trace_flags_byte = int(trace_flags, 16)
        parent_sampled = (trace_flags_byte & 0x01) == 1

    return {
        "trace_id": trace_id,
        "parent_span_id": parent_span_id,
        "parent_sampled": parent_sampled,
    }


def _format_sql(cursor, sql):
    # type: (Any, str) -> Optional[str]

    real_sql = None

    # If we're using psycopg2, it could be that we're
    # looking at a query that uses Composed objects. Use psycopg2's mogrify
    # function to format the query. We lose per-parameter trimming but gain
    # accuracy in formatting.
    try:
        if hasattr(cursor, "mogrify"):
            real_sql = cursor.mogrify(sql)
            if isinstance(real_sql, bytes):
                real_sql = real_sql.decode(cursor.connection.encoding)
    except Exception:
        real_sql = None

    return real_sql or to_string(sql)


class PropagationContext:
    """
    The PropagationContext represents the data of a trace in Sentry.
    """

    __slots__ = (
        "_trace_id",
        "_span_id",
        "parent_span_id",
        "parent_sampled",
        "dynamic_sampling_context",
    )

    def __init__(
        self,
        trace_id=None,  # type: Optional[str]
        span_id=None,  # type: Optional[str]
        parent_span_id=None,  # type: Optional[str]
        parent_sampled=None,  # type: Optional[bool]
        dynamic_sampling_context=None,  # type: Optional[Dict[str, str]]
    ):
        # type: (...) -> None
        self._trace_id = trace_id
        """The trace id of the Sentry trace."""

        self._span_id = span_id
        """The span id of the currently executing span."""

        self.parent_span_id = parent_span_id
        """The id of the parent span that started this span.
        The parent span could also be a span in an upstream service."""

        self.parent_sampled = parent_sampled
        """Boolean indicator if the parent span was sampled.
        Important when the parent span originated in an upstream service,
        because we want to sample the whole trace, or nothing from the trace."""

        self.dynamic_sampling_context = dynamic_sampling_context
        """Data that is used for dynamic sampling decisions."""

    @classmethod
    def from_incoming_data(cls, incoming_data):
        # type: (Dict[str, Any]) -> Optional[PropagationContext]
        propagation_context = None

        normalized_data = normalize_incoming_data(incoming_data)
        baggage_header = normalized_data.get(BAGGAGE_HEADER_NAME)
        if baggage_header:
            propagation_context = PropagationContext()
            propagation_context.dynamic_sampling_context = Baggage.from_incoming_header(
                baggage_header
            ).dynamic_sampling_context()

        sentry_trace_header = normalized_data.get(SENTRY_TRACE_HEADER_NAME)
        if sentry_trace_header:
            sentrytrace_data = extract_sentrytrace_data(sentry_trace_header)
            if sentrytrace_data is not None:
                if propagation_context is None:
                    propagation_context = PropagationContext()
                propagation_context.update(sentrytrace_data)

        if sentry_trace_header is None:
            w3c_trace_header = normalized_data.get(W3C_TRACE_HEADER_NAME)
            if w3c_trace_header:
                w3c_trace_data = extract_w3c_traceparent_data(w3c_trace_header)
                if w3c_trace_data is not None:
                    if propagation_context is None:
                        propagation_context = PropagationContext()
                    propagation_context.update(w3c_trace_data)

        if propagation_context is not None:
            propagation_context._fill_sample_rand()

        return propagation_context

    @property
    def trace_id(self):
        # type: () -> str
        """The trace id of the Sentry trace."""
        if not self._trace_id:
            # New trace, don't fill in sample_rand
            self._trace_id = uuid.uuid4().hex

        return self._trace_id

    @trace_id.setter
    def trace_id(self, value):
        # type: (str) -> None
        self._trace_id = value

    @property
    def span_id(self):
        # type: () -> str
        """The span id of the currently executed span."""
        if not self._span_id:
            self._span_id = uuid.uuid4().hex[16:]

        return self._span_id

    @span_id.setter
    def span_id(self, value):
        # type: (str) -> None
        self._span_id = value

    def update(self, other_dict):
        # type: (Dict[str, Any]) -> None
        """
        Updates the PropagationContext with data from the given dictionary.
        """
        for key, value in other_dict.items():
            try:
                setattr(self, key, value)
            except AttributeError:
                pass

    def __repr__(self):
        # type: (...) -> str
        return "<PropagationContext _trace_id={} _span_id={} parent_span_id={} parent_sampled={} dynamic_sampling_context={}>".format(
            self._trace_id,
            self._span_id,
            self.parent_span_id,
            self.parent_sampled,
            self.dynamic_sampling_context,
        )

    def _fill_sample_rand(self):
        # type: () -> None
        """
        Ensure that there is a valid sample_rand value in the dynamic_sampling_context.

        If there is a valid sample_rand value in the dynamic_sampling_context, we keep it.
        Otherwise, we generate a sample_rand value according to the following:

          - If we have a parent_sampled value and a sample_rate in the DSC, we compute
            a sample_rand value randomly in the range:
                - [0, sample_rate) if parent_sampled is True,
                - or, in the range [sample_rate, 1) if parent_sampled is False.

          - If either parent_sampled or sample_rate is missing, we generate a random
            value in the range [0, 1).

        The sample_rand is deterministically generated from the trace_id, if present.

        This function does nothing if there is no dynamic_sampling_context.
        """
        if self.dynamic_sampling_context is None:
            return

        sample_rand = try_convert(
            Decimal, self.dynamic_sampling_context.get("sample_rand")
        )
        if sample_rand is not None and 0 <= sample_rand < 1:
            # sample_rand is present and valid, so don't overwrite it
            return

        # Get the sample rate and compute the transformation that will map the random value
        # to the desired range: [0, 1), [0, sample_rate), or [sample_rate, 1).
        sample_rate = try_convert(
            float, self.dynamic_sampling_context.get("sample_rate")
        )
        lower, upper = _sample_rand_range(self.parent_sampled, sample_rate)

        try:
            sample_rand = _generate_sample_rand(self.trace_id, interval=(lower, upper))
        except ValueError:
            # ValueError is raised if the interval is invalid, i.e. lower >= upper.
            # lower >= upper might happen if the incoming trace's sampled flag
            # and sample_rate are inconsistent, e.g. sample_rate=0.0 but sampled=True.
            # We cannot generate a sensible sample_rand value in this case.
            logger.debug(
                f"Could not backfill sample_rand, since parent_sampled={self.parent_sampled} "
                f"and sample_rate={sample_rate}."
            )
            return

        self.dynamic_sampling_context["sample_rand"] = (
            f"{sample_rand:.6f}"  # noqa: E231
        )

    def _sample_rand(self):
        # type: () -> Optional[str]
        """Convenience method to get the sample_rand value from the dynamic_sampling_context."""
        if self.dynamic_sampling_context is None:
            return None

        return self.dynamic_sampling_context.get("sample_rand")


class Baggage:
    """
    The W3C Baggage header information (see https://www.w3.org/TR/baggage/).

    Before mutating a `Baggage` object, calling code must check that `mutable` is `True`.
    Mutating a `Baggage` object that has `mutable` set to `False` is not allowed, but
    it is the caller's responsibility to enforce this restriction.
    """

    __slots__ = ("sentry_items", "third_party_items", "mutable")

    SENTRY_PREFIX = "sentry-"
    SENTRY_PREFIX_REGEX = re.compile("^sentry-")

    def __init__(
        self,
        sentry_items,  # type: Dict[str, str]
        third_party_items="",  # type: str
        mutable=True,  # type: bool
    ):
        self.sentry_items = sentry_items
        self.third_party_items = third_party_items
        self.mutable = mutable

    @classmethod
    def from_incoming_header(
        cls,
        header,  # type: Optional[str]
        *,
        _sample_rand=None,  # type: Optional[str]
    ):
        # type: (...) -> Baggage
        """
        freeze if incoming header already has sentry baggage
        """
        sentry_items = {}
        third_party_items = ""
        mutable = True

        if header:
            for item in header.split(","):
                if "=" not in item:
                    continue

                with capture_internal_exceptions():
                    item = item.strip()
                    key, val = item.split("=")
                    if Baggage.SENTRY_PREFIX_REGEX.match(key):
                        baggage_key = unquote(key.split("-")[1])
                        sentry_items[baggage_key] = unquote(val)
                        mutable = False
                    else:
                        third_party_items += ("," if third_party_items else "") + item

        if _sample_rand is not None:
            sentry_items["sample_rand"] = str(_sample_rand)
            mutable = False

        return Baggage(sentry_items, third_party_items, mutable)

    @classmethod
    def from_options(cls, scope):
        # type: (sentry_sdk.scope.Scope) -> Optional[Baggage]

        sentry_items = {}  # type: Dict[str, str]
        third_party_items = ""
        mutable = False

        client = sentry_sdk.get_client()

        if not client.is_active() or scope._propagation_context is None:
            return Baggage(sentry_items)

        options = client.options
        propagation_context = scope._propagation_context

        if propagation_context is not None:
            sentry_items["trace_id"] = propagation_context.trace_id

        if options.get("environment"):
            sentry_items["environment"] = options["environment"]

        if options.get("release"):
            sentry_items["release"] = options["release"]

        if options.get("dsn"):
            sentry_items["public_key"] = Dsn(options["dsn"]).public_key

        if options.get("traces_sample_rate"):
            sentry_items["sample_rate"] = str(options["traces_sample_rate"])

        return Baggage(sentry_items, third_party_items, mutable)

    @classmethod
    def populate_from_transaction(cls, transaction):
        # type: (sentry_sdk.tracing.Transaction) -> Baggage
        """
        Populate fresh baggage entry with sentry_items and make it immutable
        if this is the head SDK which originates traces.
        """
        client = sentry_sdk.get_client()
        sentry_items = {}  # type: Dict[str, str]

        if not client.is_active():
            return Baggage(sentry_items)

        options = client.options or {}

        sentry_items["trace_id"] = transaction.trace_id
        sentry_items["sample_rand"] = str(transaction._sample_rand)

        if options.get("environment"):
            sentry_items["environment"] = options["environment"]

        if options.get("release"):
            sentry_items["release"] = options["release"]

        if options.get("dsn"):
            sentry_items["public_key"] = Dsn(options["dsn"]).public_key

        if (
            transaction.name
            and transaction.source not in LOW_QUALITY_TRANSACTION_SOURCES
        ):
            sentry_items["transaction"] = transaction.name

        if transaction.sample_rate is not None:
            sentry_items["sample_rate"] = str(transaction.sample_rate)

        if transaction.sampled is not None:
            sentry_items["sampled"] = "true" if transaction.sampled else "false"

        # there's an existing baggage but it was mutable,
        # which is why we are creating this new baggage.
        # However, if by chance the user put some sentry items in there, give them precedence.
        if transaction._baggage and transaction._baggage.sentry_items:
            sentry_items.update(transaction._baggage.sentry_items)

        return Baggage(sentry_items, mutable=False)

    def freeze(self):
        # type: () -> None
        self.mutable = False

    def dynamic_sampling_context(self):
        # type: () -> Dict[str, str]
        header = {}

        for key, item in self.sentry_items.items():
            header[key] = item

        return header

    def serialize(self, include_third_party=False):
        # type: (bool) -> str
        items = []

        for key, val in self.sentry_items.items():
            with capture_internal_exceptions():
                item = Baggage.SENTRY_PREFIX + quote(key) + "=" + quote(str(val))
                items.append(item)

        if include_third_party:
            items.append(self.third_party_items)

        return ",".join(items)

    @staticmethod
    def strip_sentry_baggage(header):
        # type: (str) -> str
        """Remove Sentry baggage from the given header.

        Given a Baggage header, return a new Baggage header with all Sentry baggage items removed.
        """
        return ",".join(
            (
                item
                for item in header.split(",")
                if not Baggage.SENTRY_PREFIX_REGEX.match(item.strip())
            )
        )

    def _sample_rand(self):
        # type: () -> Optional[Decimal]
        """Convenience method to get the sample_rand value from the sentry_items.

        We validate the value and parse it as a Decimal before returning it. The value is considered
        valid if it is a Decimal in the range [0, 1).
        """
        sample_rand = try_convert(Decimal, self.sentry_items.get("sample_rand"))

        if sample_rand is not None and Decimal(0) <= sample_rand < Decimal(1):
            return sample_rand

        return None

    def __repr__(self):
        # type: () -> str
        return f'<Baggage "{self.serialize(include_third_party=True)}", mutable={self.mutable}>'


def should_propagate_trace(client, url):
    # type: (sentry_sdk.client.BaseClient, str) -> bool
    """
    Returns True if url matches trace_propagation_targets configured in the given client. Otherwise, returns False.
    """
    trace_propagation_targets = client.options["trace_propagation_targets"]

    if is_sentry_url(client, url):
        return False

    return match_regex_list(url, trace_propagation_targets, substring_matching=True)


def normalize_incoming_data(incoming_data):
    # type: (Dict[str, Any]) -> Dict[str, Any]
    """
    Normalizes incoming data so the keys are all lowercase with dashes instead of underscores and stripped from known prefixes.
    """
    data = {}
    for key, value in incoming_data.items():
        if key.startswith("HTTP_"):
            key = key[5:]

        key = key.replace("_", "-").lower()
        data[key] = value

    return data


def start_child_span_decorator(func):
    # type: (Any) -> Any
    """
    Decorator to add child spans for functions.

    See also ``sentry_sdk.tracing.trace()``.
    """
    # Asynchronous case
    if inspect.iscoroutinefunction(func):

        @wraps(func)
        async def func_with_tracing(*args, **kwargs):
            # type: (*Any, **Any) -> Any

            span = get_current_span()

            if span is None:
                logger.debug(
                    "Cannot create a child span for %s. "
                    "Please start a Sentry transaction before calling this function.",
                    qualname_from_function(func),
                )
                return await func(*args, **kwargs)

            with span.start_child(
                op=OP.FUNCTION,
                name=qualname_from_function(func),
            ):
                return await func(*args, **kwargs)

        try:
            func_with_tracing.__signature__ = inspect.signature(func)  # type: ignore[attr-defined]
        except Exception:
            pass

    # Synchronous case
    else:

        @wraps(func)
        def func_with_tracing(*args, **kwargs):
            # type: (*Any, **Any) -> Any

            span = get_current_span()

            if span is None:
                logger.debug(
                    "Cannot create a child span for %s. "
                    "Please start a Sentry transaction before calling this function.",
                    qualname_from_function(func),
                )
                return func(*args, **kwargs)

            with span.start_child(
                op=OP.FUNCTION,
                name=qualname_from_function(func),
            ):
                return func(*args, **kwargs)

        try:
            func_with_tracing.__signature__ = inspect.signature(func)  # type: ignore[attr-defined]
        except Exception:
            pass

    return func_with_tracing


def get_current_span(scope=None):
    # type: (Optional[sentry_sdk.Scope]) -> Optional[Span]
    """
    Returns the currently active span if there is one running, otherwise `None`
    """
    scope = scope or sentry_sdk.get_current_scope()
    current_span = scope.span
    return current_span


def _generate_sample_rand(
    trace_id,  # type: Optional[str]
    *,
    interval=(0.0, 1.0),  # type: tuple[float, float]
):
    # type: (...) -> Decimal
    """Generate a sample_rand value from a trace ID.

    The generated value will be pseudorandomly chosen from the provided
    interval. Specifically, given (lower, upper) = interval, the generated
    value will be in the range [lower, upper). The value has 6-digit precision,
    so when printing with .6f, the value will never be rounded up.

    The pseudorandom number generator is seeded with the trace ID.
    """
    lower, upper = interval
    if not lower < upper:  # using `if lower >= upper` would handle NaNs incorrectly
        raise ValueError("Invalid interval: lower must be less than upper")

    rng = Random(trace_id)
    sample_rand = upper
    while sample_rand >= upper:
        sample_rand = rng.uniform(lower, upper)

    # Round down to exactly six decimal-digit precision.
    # Setting the context is needed to avoid an InvalidOperation exception
    # in case the user has changed the default precision.
    return Decimal(sample_rand).quantize(
        Decimal("0.000001"), rounding=ROUND_DOWN, context=Context(prec=6)
    )


def _sample_rand_range(parent_sampled, sample_rate):
    # type: (Optional[bool], Optional[float]) -> tuple[float, float]
    """
    Compute the lower (inclusive) and upper (exclusive) bounds of the range of values
    that a generated sample_rand value must fall into, given the parent_sampled and
    sample_rate values.
    """
    if parent_sampled is None or sample_rate is None:
        return 0.0, 1.0
    elif parent_sampled is True:
        return 0.0, sample_rate
    else:  # parent_sampled is False
        return sample_rate, 1.0


# Circular imports
from sentry_sdk.tracing import (
    BAGGAGE_HEADER_NAME,
    LOW_QUALITY_TRANSACTION_SOURCES,
    SENTRY_TRACE_HEADER_NAME,
    W3C_TRACE_HEADER_NAME,
)

if TYPE_CHECKING:
    from sentry_sdk.tracing import Span