⚡️ Speed up method S3DataSource.get_bucket_cors by 74%

[codeflash-ai]

📄 74% (0.74x) speedup for S3DataSource.get_bucket_cors in backend/python/app/sources/external/s3/s3.py

⏱️ Runtime : 1.13 milliseconds → 648 microseconds (best of 88 runs)

📝 Explanation and details

The key optimization is client connection reuse through a persistent S3 client object.

What changed:

• Added _s3_client_obj instance variable and _get_persistent_s3_client() method
• Instead of creating a new session.client('s3') context manager for each request, the optimized version creates one persistent client using __aenter__() and reuses it across all subsequent calls

Why this improves performance:
The original code created and tore down a new aioboto3 S3 client connection for every single get_bucket_cors call. Each async with session.client('s3') involves:

• Client initialization overhead
• Connection establishment
• Context manager setup/teardown

The line profiler shows the impact: in the original code, async with session.client('s3') as s3_client: took 24.1% of total execution time. In the optimized version, this overhead is eliminated after the first call.

Performance gains:

• 73% faster runtime (1.13ms → 648μs)
• 2.3% throughput improvement (53,320 → 54,560 ops/sec)

Best for: Workloads making multiple S3 operations on the same S3DataSource instance. The optimization shines in scenarios like the concurrent tests (100-200 requests), where connection reuse provides cumulative savings. Single-call scenarios see minimal benefit since the first call still pays the client creation cost.

✅ Correctness verification report:

Test	Status
⚙️ Existing Unit Tests	🔘 None Found
🌀 Generated Regression Tests	✅ 634 Passed
⏪ Replay Tests	🔘 None Found
🔎 Concolic Coverage Tests	🔘 None Found
📊 Tests Coverage	78.6%

🌀 Generated Regression Tests and Runtime

import asyncio  # used to run async functions
from typing import Optional

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


# --- Mock aioboto3 session and client ---
class MockS3Client:
    def __init__(self, responses):
        self.responses = responses
        self.calls = []

    async def get_bucket_cors(self, **kwargs):
        self.calls.append(kwargs)
        # Simulate error for specific buckets
        if kwargs['Bucket'] in self.responses:
            resp = self.responses[kwargs['Bucket']]
            if isinstance(resp, Exception):
                raise resp
            return resp
        # Default: return a valid CORS configuration
        return {'CORSRules': [{'AllowedMethods': ['GET'], 'AllowedOrigins': ['*']}]}

class MockSession:
    def __init__(self, responses):
        self.responses = responses

    async def __aenter__(self):
        return MockS3Client(self.responses)

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

    def client(self, service_name):
        return self

class MockAioboto3Session:
    def __init__(self, responses):
        self.responses = responses

    def client(self, service_name):
        return MockSession(self.responses)

# --- Minimal S3Client stub for dependency injection ---
class S3Client:
    def __init__(self, responses):
        self.responses = responses

    def get_session(self):
        return MockAioboto3Session(self.responses)

# --- Patch ClientError for error simulation ---
class ClientError(Exception):
    def __init__(self, response, operation_name):
        self.response = response
        self.operation_name = operation_name

# -------------------- UNIT TESTS --------------------

# 1. Basic Test Cases

@pytest.mark.asyncio
async def test_get_bucket_cors_success_basic():
    """Test basic successful CORS retrieval."""
    responses = {
        'my-bucket': {'CORSRules': [{'AllowedMethods': ['GET'], 'AllowedOrigins': ['*']}]}
    }
    s3_client = S3Client(responses)
    s3_ds = S3DataSource(s3_client)
    result = await s3_ds.get_bucket_cors('my-bucket')

@pytest.mark.asyncio
async def test_get_bucket_cors_success_with_expected_owner():
    """Test CORS retrieval with ExpectedBucketOwner parameter."""
    responses = {
        'owner-bucket': {'CORSRules': [{'AllowedMethods': ['PUT'], 'AllowedOrigins': ['https://example.com']}]}
    }
    s3_client = S3Client(responses)
    s3_ds = S3DataSource(s3_client)
    result = await s3_ds.get_bucket_cors('owner-bucket', ExpectedBucketOwner='123456789')

@pytest.mark.asyncio

async def test_get_bucket_cors_error_dict_response():
    """Test handling of error dict in response."""
    responses = {
        'error-bucket': {'Error': {'Code': 'NoSuchBucket', 'Message': 'The specified bucket does not exist'}}
    }
    s3_client = S3Client(responses)
    s3_ds = S3DataSource(s3_client)
    result = await s3_ds.get_bucket_cors('error-bucket')

# 2. Edge Test Cases

@pytest.mark.asyncio
async def test_get_bucket_cors_clienterror_exception():
    """Test handling of ClientError exception."""
    responses = {
        'fail-bucket': ClientError(
            response={'Error': {'Code': 'AccessDenied', 'Message': 'Access Denied'}},
            operation_name='GetBucketCors'
        )
    }
    s3_client = S3Client(responses)
    s3_ds = S3DataSource(s3_client)
    result = await s3_ds.get_bucket_cors('fail-bucket')

@pytest.mark.asyncio

async def test_get_bucket_cors_concurrent_requests():
    """Test concurrent execution of get_bucket_cors for different buckets."""
    responses = {
        'bucket1': {'CORSRules': [{'AllowedMethods': ['GET'], 'AllowedOrigins': ['*']}]},
        'bucket2': {'CORSRules': [{'AllowedMethods': ['POST'], 'AllowedOrigins': ['https://foo.com']}]}
    }
    s3_client = S3Client(responses)
    s3_ds = S3DataSource(s3_client)
    # Run two requests concurrently
    results = await asyncio.gather(
        s3_ds.get_bucket_cors('bucket1'),
        s3_ds.get_bucket_cors('bucket2')
    )

@pytest.mark.asyncio
async def test_get_bucket_cors_concurrent_mixed_success_and_error():
    """Test concurrent requests with mixed success and error responses."""
    responses = {
        'good-bucket': {'CORSRules': [{'AllowedMethods': ['GET'], 'AllowedOrigins': ['*']}]},
        'bad-bucket': ClientError(
            response={'Error': {'Code': 'NoSuchBucket', 'Message': 'Bucket not found'}},
            operation_name='GetBucketCors'
        )
    }
    s3_client = S3Client(responses)
    s3_ds = S3DataSource(s3_client)
    results = await asyncio.gather(
        s3_ds.get_bucket_cors('good-bucket'),
        s3_ds.get_bucket_cors('bad-bucket')
    )

# 3. Large Scale Test Cases

@pytest.mark.asyncio
async def test_get_bucket_cors_many_concurrent_requests():
    """Test large scale concurrent execution (up to 100 buckets)."""
    bucket_names = [f'bucket{i}' for i in range(100)]
    responses = {name: {'CORSRules': [{'AllowedMethods': ['GET'], 'AllowedOrigins': ['*']}]}
                 for name in bucket_names}
    s3_client = S3Client(responses)
    s3_ds = S3DataSource(s3_client)
    tasks = [s3_ds.get_bucket_cors(name) for name in bucket_names]
    results = await asyncio.gather(*tasks)
    for result in results:
        pass

@pytest.mark.asyncio
async def test_get_bucket_cors_many_concurrent_mixed_errors():
    """Test large scale concurrent execution with some buckets returning errors."""
    bucket_names = [f'bucket{i}' for i in range(50)]
    error_names = [f'error_bucket{i}' for i in range(50)]
    responses = {name: {'CORSRules': [{'AllowedMethods': ['GET'], 'AllowedOrigins': ['*']}]}
                 for name in bucket_names}
    for name in error_names:
        responses[name] = ClientError(
            response={'Error': {'Code': 'NoSuchBucket', 'Message': 'Bucket not found'}},
            operation_name='GetBucketCors'
        )
    s3_client = S3Client(responses)
    s3_ds = S3DataSource(s3_client)
    tasks = [s3_ds.get_bucket_cors(name) for name in bucket_names + error_names]
    results = await asyncio.gather(*tasks)
    for i, result in enumerate(results):
        if i < 50:
            pass
        else:
            pass

# 4. Throughput Test Cases

@pytest.mark.asyncio


async def test_get_bucket_cors_throughput_high_load():
    """Throughput test: high load (200 requests)."""
    bucket_names = [f'high_bucket{i}' for i in range(200)]
    responses = {name: {'CORSRules': [{'AllowedMethods': ['GET'], 'AllowedOrigins': ['*']}]}
                 for name in bucket_names}
    s3_client = S3Client(responses)
    s3_ds = S3DataSource(s3_client)
    tasks = [s3_ds.get_bucket_cors(name) for name in bucket_names]
    results = await asyncio.gather(*tasks)
    # Ensure all responses are unique and correct
    for i, result in enumerate(results):
        pass

@pytest.mark.asyncio
async def test_get_bucket_cors_throughput_mixed_load():
    """Throughput test: mixed load with errors (100 success, 50 errors)."""
    bucket_names = [f'mixed_bucket{i}' for i in range(100)]
    error_names = [f'mixed_error_bucket{i}' for i in range(50)]
    responses = {name: {'CORSRules': [{'AllowedMethods': ['GET'], 'AllowedOrigins': ['*']}]}
                 for name in bucket_names}
    for name in error_names:
        responses[name] = ClientError(
            response={'Error': {'Code': 'AccessDenied', 'Message': 'Access Denied'}},
            operation_name='GetBucketCors'
        )
    s3_client = S3Client(responses)
    s3_ds = S3DataSource(s3_client)
    tasks = [s3_ds.get_bucket_cors(name) for name in bucket_names + error_names]
    results = await asyncio.gather(*tasks)
    for i, result in enumerate(results):
        if i < 100:
            pass
        else:
            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
# --- Begin: Function under test (EXACT COPY, UNMODIFIED) ---
from typing import Optional
from unittest.mock import AsyncMock, MagicMock, patch

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

# --- End: Minimal stub classes ---


try:
    import aioboto3  # type: ignore
    from botocore.exceptions import ClientError  # type: ignore
except ImportError:
    # For test environment: define dummy ClientError if not installed
    class ClientError(Exception):
        def __init__(self, response=None, operation_name=None):
            self.response = response or {}
            self.operation_name = operation_name
# --- End: Function under test ---

# --- Begin: Test suite for get_bucket_cors ---

@pytest.mark.asyncio












#------------------------------------------------
from app.sources.external.s3.s3 import S3DataSource

To edit these changes git checkout codeflash/optimize-S3DataSource.get_bucket_cors-mhczwdcr and push.