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Fix: avoid uncessary retries in OAuth authenticated requests #1206

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Merged
merged 6 commits into from
Aug 22, 2025
Merged

Fix: avoid uncessary retries in OAuth authenticated requests #1206

merged 6 commits into from
Aug 22, 2025

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keurcien
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Motivation and Context

Tried to connect an MCP client to Notion's MCP client (more info here: #1204)

How Has This Been Tested?

Using a local script wrapping this code snippet:

async with streamablehttp_client("https://mcp.notion.com/mcp", auth=oauth_auth) as (read, write, _):

    async with ClientSession(read, write) as session:
        await session.initialize()
        tools = await session.list_tools()
        print(f"Available tools: {[tool.name for tool in tools.tools]}")
        resources = await session.list_resources()
        print(f"Available resources: {[r.uri for r in resources.resources]}")

        tool_result = await session.call_tool(name="search", arguments={"query": "John Doe"})

Now list_tools(), list_resources() and call_tool() run instantly.

Breaking Changes

No

Types of changes

  • Bug fix (non-breaking change which fixes an issue)
  • New feature (non-breaking change which adds functionality)
  • Breaking change (fix or feature that would cause existing functionality to change)
  • Documentation update

Checklist

  • I have read the MCP Documentation
  • My code follows the repository's style guidelines
  • New and existing tests pass locally
  • I have added appropriate error handling
  • I have added or updated documentation as needed

Additional context

@keurcien keurcien requested a review from a team as a code owner July 27, 2025 15:32
@keurcien keurcien requested a review from ochafik July 27, 2025 15:32
ochafik
ochafik previously requested changes Aug 5, 2025
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Hi @keurcien, thanks for this PR!

I wonder if you could add a test case, maybe in tests/client/test_auth.py, based on your snippet? (if it's not too involved)

@keurcien
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Sure, will do this week if I find some time

felixweinberger added a commit that referenced this pull request Aug 21, 2025
@felixweinberger
Add proper regression test for OAuth retry performance bug
fb105c9 
This test validates the fix for PR #1206 which resolved a critical
performance issue where every request was being sent twice due to
incorrect indentation of retry logic.

The test:
- Simulates a successful authenticated request (200 response)
- Counts how many times the request is yielded
- FAILS with buggy version: 2 yields (double sending)
- PASSES with fix: 1 yield (correct behavior)

This directly tests the root cause that made OAuth requests 2x slower
and ensures this regression cannot occur again.
@felixweinberger felixweinberger dismissed ochafik’s stale review August 21, 2025 15:30

Added regression test

@felixweinberger felixweinberger requested review from ochafik and removed request for ochafik August 21, 2025 15:30
@felixweinberger felixweinberger force-pushed the main branch 2 times, most recently from 5cdcb94 to ec7d9d6 Compare August 21, 2025 15:38
keurcien and others added 3 commits August 21, 2025 16:41
@keurcien @felixweinberger
Avoid retry everytime
8445068
@felixweinberger
Add proper regression test for OAuth retry performance bug
b2ec459 
This test validates the fix for PR modelcontextprotocol#1206 which resolved a critical
performance issue where every request was being sent twice due to
incorrect indentation of retry logic.

The test:
- Simulates a successful authenticated request (200 response)
- Counts how many times the request is yielded
- FAILS with buggy version: 2 yields (double sending)
- PASSES with fix: 1 yield (correct behavior)

This directly tests the root cause that made OAuth requests 2x slower
and ensures this regression cannot occur again.
@felixweinberger
lint: fix formatting
2c6c909
@felixweinberger
Fix type annotations for regression test
5f37158 
Add missing type hints to test_auth_flow_no_unnecessary_retry_after_oauth
to satisfy pyright type checking requirements.
@felixweinberger
Fix OAuth auth flow tests to properly close async generators
3b8e7b6 
The retry logic fix in PR-1206 moved the final request yield inside the OAuth
flow block, which now correctly retries requests after OAuth completion.
However, the existing tests didn't expect this final yield and would exit
the generator early, causing a GeneratorExit exception while the async lock
was still held. This resulted in RuntimeError: The current task is not
holding this lock.

Fix by properly closing the generators in both failing tests:
- test_oauth_discovery_fallback_conditions
- test_auth_flow_with_no_tokens

Both tests now send a final success response to properly complete the
auth flow generator and prevent the lock release error.
felixweinberger
felixweinberger reviewed Aug 21, 2025
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tests/client/test_auth.py
await auth_flow.asend(final_response)
except StopAsyncIteration:
pass # Expected - generator should complete

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@felixweinberger felixweinberger Aug 21, 2025 •
edited
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These tests were inadvertently tuned to the buggy behavior where requests were being unconditionally retried after every response. The indentation fix ensures retries only happen after OAuth completion (401 responses), not after successful responses. This exposed that the tests weren't properly closing the auth flow generator after the legitimate OAuth retry, causing lock release errors.

@felixweinberger
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@keurcien @ochafik went ahead and added some test coverage here + fixed failing CI which was tuned to the original behavior.

ochafik
ochafik approved these changes Aug 22, 2025
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Thanks @felixweinberger for the test updates!

@ochafik ochafik merged commit e750a06 into modelcontextprotocol:main Aug 22, 2025
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@eyalzh
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eyalzh commented Aug 24, 2025

This fix also resolves a timeout issue when using stored access tokens in SSE auth flow (happened as soon as I replaced InMemoryTokenStorage with a keychain-based token storage).

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@felixweinberger felixweinberger felixweinberger left review comments

@ochafik ochafik ochafik approved these changes

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4 participants
@keurcien @felixweinberger @eyalzh @ochafik