fix(json-rpc): add stream_send_timeout for JSON-RPC streaming endpoints

[devesh1011]

Description

This PR fixes issue #545 where JSON-RPC streaming endpoints were closing prematurely due to Starlette's default 5-second send timeout when agents take longer to respond.

Problem

JSON-RPC streaming connections using EventSourceResponse were being closed after 5 seconds by Starlette's default send_timeout, causing issues when agents need more time to process and respond to requests.

Solution

Added a configurable stream_send_timeout parameter to the JSON-RPC application classes:

Fixes #545 🦕

[gemini-code-assist]

Summary of Changes

Hello @devesh1011, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request provides a crucial fix for JSON-RPC streaming connections by introducing a configurable stream_send_timeout parameter. This enhancement prevents premature termination of streaming endpoints caused by Starlette's default timeout, ensuring that long-running agent responses can be fully delivered without interruption. The change improves the robustness and flexibility of the streaming architecture.

Highlights

• Configurable Streaming Timeout: Introduced a new stream_send_timeout parameter to JSON-RPC application classes, allowing users to configure the timeout for streaming responses.
• Addresses Premature Connection Closure: This change resolves an issue where JSON-RPC streaming endpoints were prematurely closed due to Starlette's default 5-second send_timeout, especially when agents required more time to respond.
• Enhanced Agent Responsiveness: The new parameter enables support for long-running agents by allowing the timeout to be increased or disabled, preventing connection drops during extended processing.
• Test Coverage: New test cases have been added for both FastAPI and Starlette applications to ensure the correct behavior and configurability of the stream_send_timeout parameter.

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[gemini-code-assist]

Code Review

This pull request introduces a stream_send_timeout parameter to address premature closing of JSON-RPC streaming endpoints. The implementation correctly adds the configurable timeout to JSONRPCApplication and its subclasses for FastAPI and Starlette, and applies it to EventSourceResponse. The changes are accompanied by new unit tests.

My review focuses on improving the clarity of the documentation for the new parameter and enhancing test coverage to ensure the new timeout logic is fully verified. I've identified some inconsistencies in the docstrings and an opportunity to strengthen the tests.

[gemini-code-assist]

The added tests for fastapi_app and starlette_app verify that the stream_send_timeout parameter is stored correctly on the application instance. However, they don't test that this value is actually used when creating an EventSourceResponse in this method.

To ensure the core logic of this fix is working as intended, I recommend adding a test that mocks EventSourceResponse and asserts it's called with the correct send_timeout value, covering cases where it's set on the app, None, and overridden via the context.state. This would provide more confidence in the change.

[gemini-code-assist]

The phrase 'in default timeout' is unclear. The docstring should also clarify that None disables the timeout, which is a change in the default behavior. For clarity and consistency, could you update it?

            stream_send_timeout: The timeout in seconds for sending events in
              streaming responses. Defaults to `None`, which disables the timeout.
              Set a float value to specify a timeout.

[gemini-code-assist]

This docstring is contradictory. It first says Defaults to None, which uses Starlette's default timeout, and then says None to disable. The latter is correct: None disables the timeout. This is also a change in the default behavior (from a 5s timeout to no timeout), which is important to document. Please clarify the docstring.

Suggested change

	stream_send_timeout: The timeout in seconds for sending events in
	streaming responses. Defaults to None, which uses Starlette's
	default timeout. Set to a larger value or None to disable for
	long-running agents.
	stream_send_timeout: The timeout in seconds for sending events in
	streaming responses. Defaults to `None`, which disables the timeout.
	This changes the default behavior from using Starlette's 5-second
	default. Set a float value to specify a timeout.

[gemini-code-assist]

This docstring is contradictory. It first says Defaults to None, which uses Starlette's default timeout, and then says None to disable. The latter is correct: None disables the timeout. This is also a change in the default behavior (from a 5s timeout to no timeout), which is important to document. Please clarify the docstring.

Suggested change

	stream_send_timeout: The timeout in seconds for sending events in
	streaming responses. Defaults to None, which uses Starlette's
	default timeout. Set to a larger value or None to disable for
	long-running agents.
	stream_send_timeout: The timeout in seconds for sending events in
	streaming responses. Defaults to `None`, which disables the timeout.
	This changes the default behavior from using Starlette's 5-second
	default. Set a float value to specify a timeout.