perf(traces): Cache valid span statuses in a module-level frozenset

[ericapisani]

The status setter on StreamedSpan was reconstructing a set from the SpanStatus enum on every invocation. In high-throughput tracing workloads this is a hot path, so caching the values in a module-level frozenset avoids repeated allocations.

Fixes #6207
Fixes PY-2403

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Using the following benchmarking script:

import timeit
from enum import Enum

class SpanStatus(str, Enum):
    OK = "ok"
    ERROR = "error"


# Approach 1: Current — rebuild set every call
def check_current(status):
    return status not in {e.value for e in SpanStatus}


# Approach 2: Module-level frozenset
_VALID = frozenset(e.value for e in SpanStatus)

def check_frozenset(status):
    return status not in _VALID


N = 100_000
REPEATS = 5

for label, fn in [
    ("current (set comprehension)", check_current),
    ("frozenset lookup",            check_frozenset),
]:
    # Test with a valid status (common path)
    times = timeit.repeat(lambda: fn("ok"), number=N, repeat=REPEATS)
    best = min(times)
    per_call_ns = (best / N) * 1e9
    print(f"{label:30s}  valid    {best:.4f}s / {N} calls  ({per_call_ns:.0f} ns/call)")

    # Test with an invalid status (rare path)
    times = timeit.repeat(lambda: fn("bogus"), number=N, repeat=REPEATS)
    best = min(times)
    per_call_ns = (best / N) * 1e9
    print(f"{label:30s}  invalid  {best:.4f}s / {N} calls  ({per_call_ns:.0f} ns/call)")

I was able to confirm the small bump in performance with this change:

Run 1:

current (set comprehension)     valid    0.0375s / 100000 calls  (375 ns/call)
current (set comprehension)     invalid  0.0379s / 100000 calls  (379 ns/call)
frozenset lookup                valid    0.0031s / 100000 calls  (31 ns/call)
frozenset lookup                invalid  0.0029s / 100000 calls  (29 ns/call)

Run 2:

current (set comprehension)     valid    0.0308s / 100000 calls  (308 ns/call)
current (set comprehension)     invalid  0.0311s / 100000 calls  (311 ns/call)
frozenset lookup                valid    0.0024s / 100000 calls  (24 ns/call)
frozenset lookup                invalid  0.0025s / 100000 calls  (25 ns/call)

Run 3:

current (set comprehension)     valid    0.0312s / 100000 calls  (312 ns/call)
current (set comprehension)     invalid  0.0312s / 100000 calls  (312 ns/call)
frozenset lookup                valid    0.0025s / 100000 calls  (25 ns/call)
frozenset lookup                invalid  0.0024s / 100000 calls  (24 ns/call)

[linear-code]

PY-2403 Replace creation of set on every `span.status` call with frozen set

[github-actions]

Codecov Results 📊

✅ 13 passed | Total: 13 | Pass Rate: 100% | Execution Time: 7.73s

All tests are passing successfully.

✅ Patch coverage is 100.00%. Project has 15002 uncovered lines.

Files with missing lines (1)

File	Patch %	Lines
traces.py	69.38%	⚠️ 94 Missing and 21 partials

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