litellm/tests/unit/proxy/middleware/test_gzip_middleware.py

import asyncio
import gzip
import json
from typing import Final

import pytest
from starlette.applications import Starlette
from starlette.requests import Request
from starlette.responses import JSONResponse, Response, StreamingResponse
from starlette.routing import Route
from starlette.types import ASGIApp, Message, Receive, Scope, Send

from litellm.proxy.middleware.gzip_middleware import (
    MINIMUM_SIZE_BYTES,
    OFF_LOOP_SIZE_BYTES,
    GZipBufferedResponseMiddleware,
)

LARGE_PAYLOAD = {"rows": [{"date": f"2026-09-{day:02d}", "spend": day * 1.5} for day in range(1, 31)] * 20}
STREAM_CHUNKS = tuple(json.dumps({"part": part, "pad": "x" * MINIMUM_SIZE_BYTES}).encode() for part in range(3))


async def _large_json(request: Request) -> Response:
    return JSONResponse(LARGE_PAYLOAD)


async def _small_json(request: Request) -> Response:
    return JSONResponse({"ok": True})


async def _already_encoded(request: Request) -> Response:
    return Response(b"x" * (MINIMUM_SIZE_BYTES * 4), headers={"content-encoding": "br"})


async def _with_etag(request: Request) -> Response:
    return Response(b"y" * (MINIMUM_SIZE_BYTES * 4), headers={"etag": '"v1"'})


async def _partial(request: Request) -> Response:
    return Response(b"p" * (MINIMUM_SIZE_BYTES * 4), status_code=206, headers={"content-range": "bytes 0-1999/9000"})


async def _no_transform(request: Request) -> Response:
    return Response(b"n" * (MINIMUM_SIZE_BYTES * 4), headers={"cache-control": "public, no-transform"})


async def _huge(request: Request) -> Response:
    return Response(b"z" * (OFF_LOOP_SIZE_BYTES * 2), media_type="application/json")


async def _json_stream(request: Request) -> Response:
    async def chunks():
        for chunk in STREAM_CHUNKS:
            yield chunk

    return StreamingResponse(chunks(), media_type="application/json")


APP = Starlette(
    routes=[
        Route("/large", _large_json),
        Route("/small", _small_json),
        Route("/encoded", _already_encoded),
        Route("/stream", _json_stream),
        Route("/etag", _with_etag),
        Route("/huge", _huge),
        Route("/partial", _partial),
        Route("/no-transform", _no_transform),
    ]
)
APP.add_middleware(GZipBufferedResponseMiddleware)


async def _send_messages(path: str, accept_encoding: str | None, app: ASGIApp = APP) -> tuple[Message, ...]:
    headers = [(b"accept-encoding", accept_encoding.encode())] if accept_encoding is not None else []
    scope = {"type": "http", "method": "GET", "path": path, "query_string": b"", "headers": headers}
    sent: list[Message] = []  # mutable-ok: ASGI send callback collects messages in order
    requests: Final = iter(({"type": "http.request", "body": b"", "more_body": False},))
    never_disconnects: Final = asyncio.Event()

    async def receive() -> Message:
        request: Final = next(requests, None)
        if request is not None:
            return request
        await never_disconnects.wait()
        return {"type": "http.disconnect"}

    async def send(message: Message) -> None:
        sent.append(message)

    await app(scope, receive, send)
    return tuple(sent)


def _headers(messages: tuple[Message, ...]) -> dict[str, str]:
    return {k.decode(): v.decode() for k, v in messages[0]["headers"]}


def _body(messages: tuple[Message, ...]) -> bytes:
    return b"".join(m.get("body", b"") for m in messages[1:])


@pytest.mark.parametrize("accept_encoding", ["gzip, deflate, br", "GZIP", "br;q=1, gzip;q=0.5", "x-gzip", "*"])
@pytest.mark.asyncio
async def test_large_buffered_json_is_gzipped_and_round_trips(accept_encoding):
    messages = await _send_messages("/large", accept_encoding)
    headers = _headers(messages)
    body = _body(messages)

    assert headers["content-encoding"] == "gzip"
    assert headers["vary"] == "Accept-Encoding"
    assert int(headers["content-length"]) == len(body)
    assert json.loads(gzip.decompress(body)) == LARGE_PAYLOAD
    assert len(body) < len(json.dumps(LARGE_PAYLOAD))


@pytest.mark.asyncio
async def test_body_above_off_loop_threshold_round_trips():
    messages = await _send_messages("/huge", "gzip")

    assert _headers(messages)["content-encoding"] == "gzip"
    assert gzip.decompress(_body(messages)) == b"z" * (OFF_LOOP_SIZE_BYTES * 2)


@pytest.mark.parametrize(
    ("path", "accept_encoding", "expected_vary"),
    [
        ("/large", None, "Accept-Encoding"),
        ("/large", "gzip;q=0", "Accept-Encoding"),
        ("/small", "gzip", None),
        ("/etag", "gzip", None),
        ("/stream", "gzip", None),
    ],
)
@pytest.mark.asyncio
async def test_vary_marks_every_negotiable_variant(path, accept_encoding, expected_vary):
    messages = await _send_messages(path, accept_encoding)

    assert _headers(messages).get("vary") == expected_vary


@pytest.mark.parametrize(
    ("path", "accept_encoding", "expected_encoding"),
    [
        ("/large", None, None),
        ("/large", "identity", None),
        ("/large", "gzip;q=0", None),
        ("/large", "br, gzip; q=0.0", None),
        ("/large", "*;q=0", None),
        ("/large", "*, gzip;q=0", None),
        ("/large", "gzip;q=invalid", None),
        ("/small", "gzip", None),
        ("/encoded", "gzip", "br"),
        ("/etag", "gzip", None),
        ("/stream", "gzip", None),
        ("/partial", "gzip", None),
        ("/no-transform", "gzip", None),
    ],
)
@pytest.mark.asyncio
async def test_response_passes_through_unmodified(path, accept_encoding, expected_encoding):
    with_header = await _send_messages(path, accept_encoding)
    without_header = await _send_messages(path, None)

    assert _headers(with_header).get("content-encoding") == expected_encoding
    assert _body(with_header) == _body(without_header)


@pytest.mark.asyncio
async def test_streamed_chunks_are_forwarded_one_by_one():
    messages = await _send_messages("/stream", "gzip")
    chunks = tuple(m["body"] for m in messages[1:] if m.get("body"))

    assert [m["type"] for m in messages].count("http.response.start") == 1
    assert chunks == STREAM_CHUNKS


@pytest.mark.asyncio
async def test_start_message_without_headers_key_is_still_gzipped():
    body: Final = b"h" * (MINIMUM_SIZE_BYTES * 4)

    async def headerless_app(scope: Scope, receive: Receive, send: Send) -> None:
        await send({"type": "http.response.start", "status": 200})
        await send({"type": "http.response.body", "body": body})

    messages = await _send_messages("/", "gzip", GZipBufferedResponseMiddleware(headerless_app))

    assert _headers(messages)["content-encoding"] == "gzip"
    assert gzip.decompress(_body(messages)) == body


@pytest.mark.asyncio
async def test_start_without_a_body_message_is_still_forwarded():
    async def start_only_app(scope: Scope, receive: Receive, send: Send) -> None:
        await send({"type": "http.response.start", "status": 204, "headers": [(b"x-done", b"1")]})

    messages = await _send_messages("/", "gzip", GZipBufferedResponseMiddleware(start_only_app))

    assert messages == ({"type": "http.response.start", "status": 204, "headers": [(b"x-done", b"1")]},)


def test_proxy_app_gzips_large_responses_for_clients_that_accept_it():
    from starlette.testclient import TestClient

    from litellm.proxy.proxy_server import app

    client = TestClient(app)
    compressed = client.get("/openapi.json", headers={"accept-encoding": "gzip"})
    identity = client.get("/openapi.json", headers={"accept-encoding": "identity"})

    assert compressed.headers["content-encoding"] == "gzip"
    assert int(compressed.headers["content-length"]) < int(identity.headers["content-length"])
    assert compressed.json() == identity.json()