⚡️ Speed up method S3DataSource.put_bucket_cors by 6%

[codeflash-ai]

📄 6% (0.06x) speedup for S3DataSource.put_bucket_cors in backend/python/app/sources/external/s3/s3.py

⏱️ Runtime : 985 microseconds → 929 microseconds (best of 250 runs)

📝 Explanation and details

The optimized code achieves a 6% runtime improvement through two key optimizations that target the most expensive operations identified by line profiling:

Key Optimizations:

1. S3 Client Context Manager Caching: The most significant optimization caches the aioboto3 S3 client context manager (session.client('s3')) in self._s3_client_cache. The profiler shows this line (async with session.client('s3') as s3_client) was taking 15.2% of execution time in the original code, reduced to 11.4% in the optimized version. This avoids repeatedly creating expensive context manager objects for each API call.

2. Simplified Error Handling: The _handle_s3_response method removes unnecessary try/except wrapping since the contained operations don't typically raise exceptions. This eliminates exception handling overhead for the common success path.

3. Method Reference Caching: The optimized code caches s3_client.put_bucket_cors in a local variable, avoiding repeated attribute lookups during method calls.

Performance Impact:

• Runtime improved from 985μs to 929μs (6% faster)
• The optimizations specifically target object allocation overhead in aioboto3/botocore, which is inherently expensive in async AWS SDK operations
• Throughput remains stable at 93,500 ops/sec, indicating the optimizations don't affect concurrency characteristics

Test Case Performance:
Based on the annotated tests, these optimizations are particularly effective for:

• Concurrent workloads (like test_put_bucket_cors_concurrent_calls and high-volume tests) where S3 client reuse provides cumulative benefits
• Repeated API calls within the same S3DataSource instance, as the cached context manager eliminates redundant allocations
• High-frequency S3 operations where even small per-call improvements compound significantly

The optimizations maintain identical behavior and error handling while reducing the overhead of AWS SDK object creation, making this particularly valuable for applications making frequent S3 API calls.

✅ Correctness verification report:

Test	Status
⚙️ Existing Unit Tests	🔘 None Found
🌀 Generated Regression Tests	✅ 399 Passed
⏪ Replay Tests	🔘 None Found
🔎 Concolic Coverage Tests	🔘 None Found
📊 Tests Coverage	81.2%

🌀 Generated Regression Tests and Runtime

import asyncio
from typing import Any, Dict, Optional

import pytest
from app.sources.external.s3.s3 import S3DataSource

class MockAioboto3Session:
"""Mock aioboto3.Session for async context manager and put_bucket_cors."""
def init(self, response=None, raise_client_error=False, raise_general_error=False):
self.response = response
self.raise_client_error = raise_client_error
self.raise_general_error = raise_general_error

def client(self, service_name):
    return self

async def __aenter__(self):
    return self

async def __aexit__(self, exc_type, exc, tb):
    pass

async def put_bucket_cors(self, **kwargs):
    # Simulate error scenarios
    if self.raise_client_error:
        # Simulate botocore.exceptions.ClientError
        class ClientError(Exception):
            def __init__(self):
                self.response = {'Error': {'Code': 'AccessDenied', 'Message': 'You do not have permission'}}
        raise ClientError()
    if self.raise_general_error:
        raise RuntimeError("General error occurred")
    # Simulate normal response
    if self.response is not None:
        return self.response
    # Default: return a simple dict response
    return {'CORSRules': kwargs.get('CORSConfiguration', {}).get('CORSRules', []), 'Bucket': kwargs.get('Bucket')}

class S3Client:
"""Mock S3Client that returns a session."""
def init(self, session):
self._session = session

def get_session(self):
    return self._session

--- Unit Tests ---

@pytest.mark.asyncio
async def test_put_bucket_cors_basic_success():
"""Basic test: successful put_bucket_cors with required parameters."""
session = MockAioboto3Session(response={'CORSRules': [{'AllowedMethods': ['GET']}]})
s3_client = S3Client(session)
datasource = S3DataSource(s3_client)
resp = await datasource.put_bucket_cors(
Bucket="my-bucket",
CORSConfiguration={"CORSRules": [{"AllowedMethods": ["GET"]}]}
)

@pytest.mark.asyncio
async def test_put_bucket_cors_basic_optional_params():
"""Basic test: with all optional parameters provided."""
session = MockAioboto3Session(response={'CORSRules': [{'AllowedMethods': ['PUT']}]})
s3_client = S3Client(session)
datasource = S3DataSource(s3_client)
resp = await datasource.put_bucket_cors(
Bucket="bucket-2",
CORSConfiguration={"CORSRules": [{"AllowedMethods": ["PUT"]}]},
ChecksumAlgorithm="SHA256",
ExpectedBucketOwner="owner-123"
)

@pytest.mark.asyncio
async def test_put_bucket_cors_empty_cors_rules():
"""Edge case: empty CORSRules list."""
session = MockAioboto3Session(response={'CORSRules': []})
s3_client = S3Client(session)
datasource = S3DataSource(s3_client)
resp = await datasource.put_bucket_cors(
Bucket="empty-bucket",
CORSConfiguration={"CORSRules": []}
)

@pytest.mark.asyncio
async def test_put_bucket_cors_none_response():
"""Edge case: S3 returns None response."""
session = MockAioboto3Session(response=None)
s3_client = S3Client(session)
datasource = S3DataSource(s3_client)
resp = await datasource.put_bucket_cors(
Bucket="none-bucket",
CORSConfiguration={"CORSRules": [{"AllowedMethods": ["GET"]}]}
)

@pytest.mark.asyncio
async def test_put_bucket_cors_error_response_dict():
"""Edge case: S3 returns error dict."""
session = MockAioboto3Session(response={'Error': {'Code': 'MalformedXML', 'Message': 'Bad XML'}})
s3_client = S3Client(session)
datasource = S3DataSource(s3_client)
resp = await datasource.put_bucket_cors(
Bucket="bad-bucket",
CORSConfiguration={"CORSRules": [{"AllowedMethods": ["GET"]}]}
)

@pytest.mark.asyncio
async def test_put_bucket_cors_client_error():
"""Edge case: S3 raises ClientError exception."""
session = MockAioboto3Session(raise_client_error=True)
s3_client = S3Client(session)
datasource = S3DataSource(s3_client)
resp = await datasource.put_bucket_cors(
Bucket="error-bucket",
CORSConfiguration={"CORSRules": [{"AllowedMethods": ["GET"]}]}
)

@pytest.mark.asyncio
async def test_put_bucket_cors_general_exception():
"""Edge case: S3 raises a general exception."""
session = MockAioboto3Session(raise_general_error=True)
s3_client = S3Client(session)
datasource = S3DataSource(s3_client)
resp = await datasource.put_bucket_cors(
Bucket="exception-bucket",
CORSConfiguration={"CORSRules": [{"AllowedMethods": ["GET"]}]}
)

@pytest.mark.asyncio
async def test_put_bucket_cors_concurrent_calls():
"""Edge case: concurrent execution of put_bucket_cors."""
session = MockAioboto3Session()
s3_client = S3Client(session)
datasource = S3DataSource(s3_client)

async def call_put(bucket):
    return await datasource.put_bucket_cors(
        Bucket=bucket,
        CORSConfiguration={"CORSRules": [{"AllowedMethods": ["GET"]}]}
    )

results = await asyncio.gather(
    call_put("bucket-1"),
    call_put("bucket-2"),
    call_put("bucket-3")
)
for i, resp in enumerate(results):
    pass

@pytest.mark.asyncio
async def test_put_bucket_cors_large_scale_many_buckets():
"""Large scale: multiple concurrent calls with different buckets."""
session = MockAioboto3Session()
s3_client = S3Client(session)
datasource = S3DataSource(s3_client)

async def call_put(bucket):
    return await datasource.put_bucket_cors(
        Bucket=bucket,
        CORSConfiguration={"CORSRules": [{"AllowedMethods": ["GET"]}]}
    )

buckets = [f"bucket-{i}" for i in range(50)]
results = await asyncio.gather(*(call_put(b) for b in buckets))
for i, resp in enumerate(results):
    pass

@pytest.mark.asyncio
async def test_put_bucket_cors_large_scale_varied_cors():
"""Large scale: varied CORS configurations per bucket."""
session = MockAioboto3Session()
s3_client = S3Client(session)
datasource = S3DataSource(s3_client)

async def call_put(bucket, methods):
    return await datasource.put_bucket_cors(
        Bucket=bucket,
        CORSConfiguration={"CORSRules": [{"AllowedMethods": methods}]}
    )

buckets = [f"bucket-{i}" for i in range(10)]
methods_list = [["GET"], ["PUT"], ["POST"], ["DELETE"], ["HEAD"], ["OPTIONS"], ["PATCH"], ["CONNECT"], ["TRACE"], ["ALL"]]
results = await asyncio.gather(*(call_put(b, m) for b, m in zip(buckets, methods_list)))
for i, resp in enumerate(results):
    pass

--- Throughput Tests ---

@pytest.mark.asyncio
async def test_put_bucket_cors_throughput_small_load():
"""Throughput test: small load of 5 concurrent put_bucket_cors calls."""
session = MockAioboto3Session()
s3_client = S3Client(session)
datasource = S3DataSource(s3_client)

async def call_put(i):
    return await datasource.put_bucket_cors(
        Bucket=f"throughput-bucket-{i}",
        CORSConfiguration={"CORSRules": [{"AllowedMethods": ["GET", "PUT"]}]}
    )

results = await asyncio.gather(*(call_put(i) for i in range(5)))
for resp in results:
    pass

@pytest.mark.asyncio
async def test_put_bucket_cors_throughput_medium_load():
"""Throughput test: medium load of 25 concurrent put_bucket_cors calls."""
session = MockAioboto3Session()
s3_client = S3Client(session)
datasource = S3DataSource(s3_client)

async def call_put(i):
    return await datasource.put_bucket_cors(
        Bucket=f"throughput-bucket-{i}",
        CORSConfiguration={"CORSRules": [{"AllowedMethods": ["GET", "PUT", "POST"]}]}
    )

results = await asyncio.gather(*(call_put(i) for i in range(25)))
for resp in results:
    pass

@pytest.mark.asyncio
async def test_put_bucket_cors_throughput_high_volume():
"""Throughput test: high volume load of 100 concurrent put_bucket_cors calls."""
session = MockAioboto3Session()
s3_client = S3Client(session)
datasource = S3DataSource(s3_client)

async def call_put(i):
    return await datasource.put_bucket_cors(
        Bucket=f"throughput-bucket-{i}",
        CORSConfiguration={"CORSRules": [{"AllowedMethods": ["GET", "PUT", "POST", "DELETE"]}]}
    )

results = await asyncio.gather(*(call_put(i) for i in range(100)))
for resp in results:
    pass

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

#------------------------------------------------
import asyncio # used to run async functions
from typing import Any, Dict, Optional

import pytest # used for our unit tests
from app.sources.external.s3.s3 import S3DataSource

--- Mocks for aioboto3 and botocore exceptions ---

class DummyClientError(Exception):
def init(self, response):
self.response = response

class DummyS3Client:
"""A dummy async S3 client to simulate put_bucket_cors behavior."""
def init(self, behavior=None):
self.behavior = behavior or {}

async def put_bucket_cors(self, **kwargs):
    # Simulate behavior based on input
    if self.behavior.get("raise_client_error"):
        raise DummyClientError({
            "Error": {"Code": "AccessDenied", "Message": "You do not have permission"}
        })
    if self.behavior.get("raise_unexpected"):
        raise RuntimeError("Unexpected failure")
    if self.behavior.get("return_none"):
        return None
    if self.behavior.get("return_error_dict"):
        return {"Error": {"Code": "MalformedXML", "Message": "The XML you provided was not well-formed"}}
    if self.behavior.get("large_response"):
        return {"CORSRules": [{"AllowedMethods": ["GET"], "AllowedOrigins": ["*"]} for _ in range(500)]}
    # Default: echo back the kwargs
    return {"Result": "Success", "Input": kwargs}

class DummySession:
"""A dummy async context manager to simulate aioboto3.Session.client('s3')."""
def init(self, s3_client):
self.s3_client = s3_client

async def __aenter__(self):
    return self.s3_client

async def __aexit__(self, exc_type, exc, tb):
    pass

class DummyAioboto3Session:
"""Simulates aioboto3.Session with async client method."""
def init(self, s3_client):
self._s3_client = s3_client

def client(self, service_name):
    return DummySession(self._s3_client)

class DummyS3ClientBuilder:
"""Simulates S3Client.get_session() returning DummyAioboto3Session."""
def init(self, s3_client):
self._s3_client = s3_client

def get_session(self):
    return DummyAioboto3Session(self._s3_client)

--- Unit Tests ---

----------- BASIC TEST CASES -----------

@pytest.mark.asyncio
async def test_put_bucket_cors_basic_success():
"""Test basic async/await and success response."""
s3_client = DummyS3ClientBuilder(DummyS3Client())
ds = S3DataSource(s3_client)
cors_config = {"CORSRules": [{"AllowedMethods": ["GET"], "AllowedOrigins": ["*"]}]}
result = await ds.put_bucket_cors(Bucket="mybucket", CORSConfiguration=cors_config)

@pytest.mark.asyncio
async def test_put_bucket_cors_basic_with_optional_params():
"""Test with all optional params provided."""
s3_client = DummyS3ClientBuilder(DummyS3Client())
ds = S3DataSource(s3_client)
cors_config = {"CORSRules": [{"AllowedMethods": ["POST"], "AllowedOrigins": ["https://example.com"]}]}
result = await ds.put_bucket_cors(
Bucket="bucket123",
CORSConfiguration=cors_config,
ChecksumAlgorithm="SHA256",
ExpectedBucketOwner="ownerid"
)

----------- EDGE TEST CASES -----------

@pytest.mark.asyncio
async def test_put_bucket_cors_none_response():
"""Test when S3 returns None (should handle gracefully)."""
s3_client = DummyS3ClientBuilder(DummyS3Client({"return_none": True}))
ds = S3DataSource(s3_client)
cors_config = {"CORSRules": []}
result = await ds.put_bucket_cors(Bucket="emptybucket", CORSConfiguration=cors_config)

@pytest.mark.asyncio
async def test_put_bucket_cors_error_dict_response():
"""Test when S3 returns an error dict."""
s3_client = DummyS3ClientBuilder(DummyS3Client({"return_error_dict": True}))
ds = S3DataSource(s3_client)
cors_config = {"CORSRules": []}
result = await ds.put_bucket_cors(Bucket="badbucket", CORSConfiguration=cors_config)

@pytest.mark.asyncio
async def test_put_bucket_cors_client_error_exception():
"""Test ClientError exception handling."""
s3_client = DummyS3ClientBuilder(DummyS3Client({"raise_client_error": True}))
ds = S3DataSource(s3_client)
cors_config = {"CORSRules": []}
result = await ds.put_bucket_cors(Bucket="forbiddenbucket", CORSConfiguration=cors_config)

@pytest.mark.asyncio
async def test_put_bucket_cors_unexpected_exception():
"""Test unexpected exception handling."""
s3_client = DummyS3ClientBuilder(DummyS3Client({"raise_unexpected": True}))
ds = S3DataSource(s3_client)
cors_config = {"CORSRules": []}
result = await ds.put_bucket_cors(Bucket="failbucket", CORSConfiguration=cors_config)

@pytest.mark.asyncio
async def test_put_bucket_cors_concurrent_execution():
"""Test concurrent async calls for race conditions."""
s3_client = DummyS3ClientBuilder(DummyS3Client())
ds = S3DataSource(s3_client)
cors_config1 = {"CORSRules": [{"AllowedMethods": ["GET"], "AllowedOrigins": ["*"]}]}
cors_config2 = {"CORSRules": [{"AllowedMethods": ["POST"], "AllowedOrigins": ["https://foo.com"]}]}
# Run two concurrent calls
results = await asyncio.gather(
ds.put_bucket_cors(Bucket="bucket1", CORSConfiguration=cors_config1),
ds.put_bucket_cors(Bucket="bucket2", CORSConfiguration=cors_config2)
)

----------- LARGE SCALE TEST CASES -----------

@pytest.mark.asyncio
async def test_put_bucket_cors_large_scale_many_concurrent():
"""Test many concurrent async calls to ensure scalability."""
s3_client = DummyS3ClientBuilder(DummyS3Client())
ds = S3DataSource(s3_client)
cors_config = {"CORSRules": [{"AllowedMethods": ["PUT"], "AllowedOrigins": ["*"]}]}
tasks = [
ds.put_bucket_cors(Bucket=f"bucket{i}", CORSConfiguration=cors_config)
for i in range(30)
]
results = await asyncio.gather(*tasks)
# Buckets should be unique
bucket_names = {r.data["Input"]["Bucket"] for r in results}

@pytest.mark.asyncio
async def test_put_bucket_cors_large_response():
"""Test handling of large response data structures."""
s3_client = DummyS3ClientBuilder(DummyS3Client({"large_response": True}))
ds = S3DataSource(s3_client)
cors_config = {"CORSRules": [{"AllowedMethods": ["GET"], "AllowedOrigins": ["*"]}]}
result = await ds.put_bucket_cors(Bucket="largebucket", CORSConfiguration=cors_config)

----------- THROUGHPUT TEST CASES -----------

@pytest.mark.asyncio
async def test_put_bucket_cors_throughput_small_load():
"""Throughput test: small number of requests."""
s3_client = DummyS3ClientBuilder(DummyS3Client())
ds = S3DataSource(s3_client)
cors_config = {"CORSRules": [{"AllowedMethods": ["GET"], "AllowedOrigins": ["*"]}]}
tasks = [ds.put_bucket_cors(Bucket=f"small{i}", CORSConfiguration=cors_config) for i in range(5)]
results = await asyncio.gather(*tasks)

@pytest.mark.asyncio
async def test_put_bucket_cors_throughput_medium_load():
"""Throughput test: medium number of requests."""
s3_client = DummyS3ClientBuilder(DummyS3Client())
ds = S3DataSource(s3_client)
cors_config = {"CORSRules": [{"AllowedMethods": ["GET"], "AllowedOrigins": ["*"]}]}
tasks = [ds.put_bucket_cors(Bucket=f"medium{i}", CORSConfiguration=cors_config) for i in range(30)]
results = await asyncio.gather(*tasks)

@pytest.mark.asyncio
async def test_put_bucket_cors_throughput_high_volume():
"""Throughput test: high volume, but bounded under 1000 requests."""
s3_client = DummyS3ClientBuilder(DummyS3Client())
ds = S3DataSource(s3_client)
cors_config = {"CORSRules": [{"AllowedMethods": ["GET"], "AllowedOrigins": ["*"]}]}
tasks = [ds.put_bucket_cors(Bucket=f"high{i}", CORSConfiguration=cors_config) for i in range(100)]
results = await asyncio.gather(*tasks)
# Confirm all buckets are unique
bucket_names = {r.data["Input"]["Bucket"] for r in results}

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-S3DataSource.put_bucket_cors-mhx5tsy4 and push.