Implement thread safety to prevent race conditions

preritdas commented 3 months ago

Fixes #41 and fixes #47.

This PR implements thread safety measures in the BigDBMClient class to prevent race conditions, particularly in access token management. Here's a detailed explanation of the changes made and their rationale:

Changes to BigDBMClient class:

Added a threading lock:

from threading import Lock

class BigDBMClient:
   def __init__(self, ...):
       ...
       self._token_lock = Lock()

This creates a single instance of Lock() for each BigDBMClient instance.

Protected token-related methods with the lock:

def _update_token(self) -> None:
   with self._token_lock:
       # Token update logic

def _access_token_valid(self) -> bool:
   with self._token_lock:
       # Token validation logic

def __request(self, request: Request) -> dict:
   with self._token_lock:
       if not self._access_token_valid():
           self._update_token()
       # Rest of the request logic

Explanation of Lock Usage and Race Conditions:

The decision to use a single Lock() instance per BigDBMClient is based on several factors:

Shared Resource Protection: The lock protects shared resources (access token and its expiration time) within a single BigDBMClient instance.
Instance-level Concurrency: Each BigDBMClient instance represents a client with its own credentials and token. The lock ensures thread-safety within an instance without unnecessary synchronization across different instances.
Efficiency: Using a single lock per instance minimizes the overhead of lock creation and management.
Granularity: The single lock provides appropriate granularity, protecting all interdependent token-related operations.
Simplicity: A single lock for all token operations keeps the code simple and easy to understand.
Race Condition Prevention: The lock effectively prevents race conditions where multiple threads might simultaneously attempt to update or check the token.

This implementation assumes that each BigDBMClient instance may be used by multiple threads, but different instances are independent.

Test Implementation:

To verify the thread safety of the BigDBMClient class, we implemented a concise yet effective test in tests/test_client.py:

The test uses a ThreadPoolExecutor with 3 workers to simulate concurrent access.
It performs 10 concurrent operations that update the token, check its validity, and access it.
The test passes if no exceptions are raised during these concurrent operations, confirming that the class behaves correctly under concurrent access.

This test effectively simulates real-world concurrent usage of the BigDBMClient and verifies that our thread safety measures prevent race conditions in token management.

Summary by CodeRabbit

New Features
- Introduced thread safety for the BigDBMClient class, enhancing the reliability of token management in multi-threaded environments.
Tests
- Added unit tests to ensure thread safety of the BigDBMClient, simulating concurrent access to validate functionality.

coderabbitai[bot] commented 3 months ago

Walkthrough

The recent updates to the BigDBMClient class enhance its thread safety through the implementation of a locking mechanism, allowing safe concurrent access to access tokens. This adjustment effectively mitigates race conditions and increases the client's reliability in multi-threaded applications. Additionally, a comprehensive suite of unit tests has been created to validate the effectiveness of these changes.

Changes

Files	Change Summary
`bigdbm/client.py`	Added `threading.Lock` for thread safety in the methods `_update_token`, `_access_token_valid`, and `__request`. Documentation updated to reflect thread safety.
`tests/test_client.py`	Introduced unit tests for `BigDBMClient`, focusing on thread safety during concurrent operations, with handling for environment variables for credentials.

Assessment against linked issues

Objective	Addressed	Explanation
Implement thread safety in `BigDBMClient` (41)	✅
Protect access to token-related methods (41)	✅
Ensure client can handle concurrent requests (41)	✅

Poem

In the world of threads that race,
A rabbit hops with gentle grace.
Locks now guard the token's stash,
Preventing any token clash.
With tests in place, we dance with glee,
Thread safety's here, oh joy for me! 🐇✨

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preritdas commented 3 months ago

Since opening this PR, tests have been taking 40+ minutes. Making changes and retrying. Canceled hanging tests.

preritdas commented 3 months ago

@coderabbitai resolve

coderabbitai[bot] commented 3 months ago

Actions performed

Comments resolved.

preritdas commented 3 months ago

@coderabbitai is there any unnecessary overuse of thread locking that could slow down concurrency?

coderabbitai[bot] commented 3 months ago

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Analysis chain

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Scripts executed

The following scripts were executed for the analysis: Script: ```shell #!/bin/bash # Search for the implementation of the `_update_token`, `_access_token_valid`, and `__request` methods in the `BigDBMClient` class. ast-grep --lang python --pattern $'class BigDBMClient { $$$ def _update_token(self) { $$$ } $$$ def _access_token_valid(self) { $$$ } $$$ def __request(self, request) { $$$ } $$$ }' ``` Length of output: 559 --- Script: ```shell #!/bin/bash # Search for the implementation of the `_update_token` method in the `BigDBMClient` class. ast-grep --lang python --pattern $'def _update_token(self):\n $$$' # Search for the implementation of the `_access_token_valid` method in the `BigDBMClient` class. ast-grep --lang python --pattern $'def _access_token_valid(self):\n $$$' # Search for the implementation of the `__request` method in the `BigDBMClient` class. ast-grep --lang python --pattern $'def __request(self, request):\n $$$' ``` Length of output: 220 --- Script: ```shell #!/bin/bash # Use rg to search for the `_update_token` method in the codebase. rg 'def _update_token$self$:' -A 10 # Use rg to search for the `_access_token_valid` method in the codebase. rg 'def _access_token_valid$self$:' -A 10 # Use rg to search for the `__request` method in the codebase. rg 'def __request$self, request$:' -A 10 ``` Length of output: 130 --- Script: ```shell #!/bin/bash # Find the `bigdbm/client.py` file. fd 'client.py' --exec rg 'def _update_token$self$:' -A 10 fd 'client.py' --exec rg 'def _access_token_valid$self$:' -A 10 fd 'client.py' --exec rg 'def __request$self, request$:' -A 10 ``` Length of output: 190 --- Script: ```shell #!/bin/bash # Locate the `bigdbm/client.py` file. fd 'client.py' # Assuming the file is found, search for the method definitions within it. # Replace `path/to/client.py` with the actual path found. rg 'def _update_token$self$:' -A 10 path/to/client.py rg 'def _access_token_valid$self$:' -A 10 path/to/client.py rg 'def __request$self, request$:' -A 10 path/to/client.py ``` Length of output: 411

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