⚡️ Speed up function make_basic_auth_response by 38%

[codeflash-ai]

📄 38% (0.38x) speedup for make_basic_auth_response in mlflow/server/auth/__init__.py

⏱️ Runtime : 8.70 milliseconds → 6.32 milliseconds (best of 70 runs)

📝 Explanation and details

The optimization replaces Flask's make_response() function with direct Response object creation, achieving a 37% speedup by eliminating unnecessary overhead.

Key Changes:

• Removed make_response() wrapper: The original code used make_response() then modified attributes separately, while the optimized version creates the Response object directly with all parameters
• Consolidated initialization: Status code, headers, and mimetype are set during object creation rather than through separate attribute assignments
• Removed import: No longer imports make_response since it's not used

Why This Is Faster:
The line profiler shows the bottleneck was in make_response() (79.8% of total time, ~31ms). This function adds validation and conversion overhead that's unnecessary when we already have the exact parameters needed. Direct Response construction bypasses this wrapper layer, reducing the per-hit time from 11,784ns to 10,525ns.

Performance Benefits:

• All test cases show 38-51% speedup in individual function calls
• Particularly effective for repeated calls (49.5% faster on second call in repeatability test)
• Large-scale scenarios benefit significantly since this eliminates per-call overhead

Impact on Authentication Workloads:
This function generates HTTP 401 responses for unauthenticated requests in MLflow's auth system. Since authentication checks occur on most API requests, this optimization reduces response time for every unauthorized access attempt, improving overall server responsiveness under authentication load.

✅ Correctness verification report:

Test	Status
⚙️ Existing Unit Tests	🔘 None Found
🌀 Generated Regression Tests	✅ 1326 Passed
⏪ Replay Tests	🔘 None Found
🔎 Concolic Coverage Tests	🔘 None Found
📊 Tests Coverage	100.0%

🌀 Generated Regression Tests and Runtime

import pytest # used for our unit tests

function to test

from flask import Flask, Response, make_response
from mlflow.server.auth.init import make_basic_auth_response

unit tests

@pytest.fixture(scope="module")
def app():
# Create a minimal Flask app for context
app = Flask(name)
return app

def test_basic_auth_response_status_code(app):
# Basic: Ensure status code is 401
with app.app_context():
codeflash_output = make_basic_auth_response(); resp = codeflash_output # 28.0μs -> 19.7μs (42.2% faster)

def test_basic_auth_response_www_authenticate_header(app):
# Basic: Ensure WWW-Authenticate header is set correctly
with app.app_context():
codeflash_output = make_basic_auth_response(); resp = codeflash_output # 27.2μs -> 19.3μs (41.1% faster)

def test_basic_auth_response_body_content(app):
# Basic: Ensure response body contains expected message and URL
with app.app_context():
codeflash_output = make_basic_auth_response(); resp = codeflash_output # 26.6μs -> 19.0μs (40.3% faster)
data = resp.get_data(as_text=True)

def test_basic_auth_response_content_type(app):
# Edge: Ensure Content-Type is text/html or text/plain (Flask default is text/html)
with app.app_context():
codeflash_output = make_basic_auth_response(); resp = codeflash_output # 26.6μs -> 19.3μs (38.1% faster)

def test_basic_auth_response_no_extra_headers(app):
# Edge: Ensure only expected headers are present (besides Flask defaults)
with app.app_context():
codeflash_output = make_basic_auth_response(); resp = codeflash_output # 26.8μs -> 19.0μs (41.1% faster)
# Flask may add Content-Type, Content-Length, etc.
# We check that WWW-Authenticate is present and correct, and nothing custom/unexpected is added
expected_headers = set(["WWW-Authenticate", "Content-Type", "Content-Length"])
# Allow for possible charset in Content-Type
for header in resp.headers:
pass

def test_basic_auth_response_is_repeatable(app):
# Edge: Ensure calling the function multiple times yields independent, identical results
with app.app_context():
codeflash_output = make_basic_auth_response(); resp1 = codeflash_output # 27.4μs -> 19.7μs (39.0% faster)
codeflash_output = make_basic_auth_response(); resp2 = codeflash_output # 11.3μs -> 7.58μs (49.5% faster)

def test_basic_auth_response_large_scale_multiple_calls(app):
# Large Scale: Call the function 500 times and check all responses are correct
with app.app_context():
for _ in range(500):
codeflash_output = make_basic_auth_response(); resp = codeflash_output
data = resp.get_data(as_text=True)

def test_basic_auth_response_header_case_insensitivity(app):
# Edge: HTTP headers are case-insensitive, test access with different casing
with app.app_context():
codeflash_output = make_basic_auth_response(); resp = codeflash_output # 27.1μs -> 19.3μs (40.7% faster)

def test_basic_auth_response_content_length_matches_body(app):
# Edge: Ensure Content-Length header matches actual body length
with app.app_context():
codeflash_output = make_basic_auth_response(); resp = codeflash_output # 26.8μs -> 19.4μs (38.1% faster)
data = resp.get_data()
content_length = int(resp.headers["Content-Length"])

def test_basic_auth_response_does_not_modify_global_state(app):
# Edge: Ensure no global state is modified (statelessness)
with app.app_context():
before = dict(globals())
codeflash_output = make_basic_auth_response(); resp = codeflash_output # 27.0μs -> 19.2μs (40.3% faster)
after = dict(globals())
# Only allow 'resp' to be added
diff = {k: after[k] for k in after if k not in before}

def test_basic_auth_response_body_is_str(app):
# Edge: Ensure response body is a string (not bytes) when decoded
with app.app_context():
codeflash_output = make_basic_auth_response(); resp = codeflash_output # 27.1μs -> 19.0μs (42.5% faster)
data = resp.get_data(as_text=True)

def test_basic_auth_response_body_exact_match(app):
# Edge: Check that the body matches exactly the expected string
with app.app_context():
codeflash_output = make_basic_auth_response(); resp = codeflash_output # 26.8μs -> 19.0μs (41.0% faster)
expected = (
"You are not authenticated. Please see "
"https://www.mlflow.org/docs/latest/auth/index.html#authenticating-to-mlflow "
"on how to authenticate."
)

def test_basic_auth_response_large_scale_content(app):
# Large Scale: Simulate verifying the response body for a large number of calls
with app.app_context():
expected = (
"You are not authenticated. Please see "
"https://www.mlflow.org/docs/latest/auth/index.html#authenticating-to-mlflow "
"on how to authenticate."
)
for _ in range(300):
codeflash_output = make_basic_auth_response(); resp = codeflash_output

def test_basic_auth_response_integration_with_flask_client(app):
# Large Scale: Use Flask test client to simulate a route using this response
with app.app_context():
test_app = app

    @test_app.route("/test-auth")
    def test_auth():
        return make_basic_auth_response()

    client = test_app.test_client()
    response = client.get("/test-auth")

codeflash_output is used to check that the output of the original code is the same as that of the optimized code.

#------------------------------------------------
import pytest # used for our unit tests
from flask import Flask, Response
from mlflow.server.auth.init import make_basic_auth_response
from werkzeug.datastructures import Headers

unit tests

---- Basic Test Cases ----

def test_response_type():
"""Test that the function returns a Flask Response object."""
with Flask(name).app_context():
codeflash_output = make_basic_auth_response(); resp = codeflash_output # 28.4μs -> 19.1μs (48.2% faster)

def test_response_status_code():
"""Test that the response status code is 401 (Unauthorized)."""
with Flask(name).app_context():
codeflash_output = make_basic_auth_response(); resp = codeflash_output # 27.3μs -> 18.2μs (50.0% faster)

def test_response_www_authenticate_header():
"""Test that the WWW-Authenticate header is set correctly."""
with Flask(name).app_context():
codeflash_output = make_basic_auth_response(); resp = codeflash_output # 27.2μs -> 18.0μs (51.2% faster)

def test_response_body_content():
"""Test that the response body contains the expected authentication message and documentation link."""
with Flask(name).app_context():
codeflash_output = make_basic_auth_response(); resp = codeflash_output # 27.0μs -> 19.3μs (39.6% faster)
body = resp.get_data(as_text=True)

---- Edge Test Cases ----

def test_response_headers_case_insensitivity():
"""Test that header access is case-insensitive (as per WSGI spec)."""
with Flask(name).app_context():
codeflash_output = make_basic_auth_response(); resp = codeflash_output # 27.5μs -> 19.2μs (42.9% faster)

def test_response_headers_are_not_mutated():
"""Test that mutating the returned headers does not affect subsequent calls (no global state)."""
with Flask(name).app_context():
codeflash_output = make_basic_auth_response(); resp1 = codeflash_output # 26.7μs -> 18.1μs (47.1% faster)
resp1.headers["WWW-Authenticate"] = "Basic realm=changed"
codeflash_output = make_basic_auth_response(); resp2 = codeflash_output # 11.3μs -> 7.67μs (47.2% faster)

def test_response_body_is_str():
"""Test that the response body is a string and not bytes when decoded."""
with Flask(name).app_context():
codeflash_output = make_basic_auth_response(); resp = codeflash_output # 27.4μs -> 18.4μs (49.1% faster)
body = resp.get_data(as_text=True)

def test_response_headers_do_not_contain_unexpected_keys():
"""Test that the response headers do not contain unexpected authentication-related keys."""
with Flask(name).app_context():
codeflash_output = make_basic_auth_response(); resp = codeflash_output # 27.3μs -> 18.8μs (44.9% faster)
unexpected_headers = ["Authorization", "Proxy-Authenticate"]
for h in unexpected_headers:
pass

def test_response_is_not_redirect():
"""Test that the response is not a redirect (status code 3xx, Location header)."""
with Flask(name).app_context():
codeflash_output = make_basic_auth_response(); resp = codeflash_output # 27.5μs -> 18.3μs (49.8% faster)

---- Large Scale Test Cases ----

def test_large_batch_response_creation_and_memory():
"""Test that creating a large number of responses does not cause memory or performance issues."""
import gc
with Flask(name).app_context():
responses = []
for _ in range(500): # Reasonable batch for unit test
codeflash_output = make_basic_auth_response(); resp = codeflash_output
responses.append(resp)
# Clean up to avoid memory leaks
del responses
gc.collect()

def test_response_determinism():
"""Test that repeated calls produce identical outputs (deterministic)."""
with Flask(name).app_context():
codeflash_output = make_basic_auth_response(); resp1 = codeflash_output # 27.3μs -> 18.7μs (45.8% faster)
codeflash_output = make_basic_auth_response(); resp2 = codeflash_output # 11.0μs -> 7.54μs (45.9% faster)

---- Clean Code and Readability Test ----

def test_response_has_no_extra_headers():
"""Test that the response does not have extra headers beyond those expected for this use case."""
with Flask(name).app_context():
codeflash_output = make_basic_auth_response(); resp = codeflash_output # 27.1μs -> 18.8μs (44.4% faster)
# Only standard headers plus WWW-Authenticate
allowed_headers = {"Content-Type", "Content-Length", "WWW-Authenticate"}
for header in resp.headers.keys():
pass

codeflash_output is used to check that the output of the original code is the same as that of the optimized code.

To edit these changes git checkout codeflash/optimize-make_basic_auth_response-mhun88g7 and push.