feat: lmprove MCP langflow port selection and error handling

[edwinjosechittilappilly]

This pull request introduces several improvements to the MCPToolsComponent and MCPSseClient classes, focusing on better error handling, validation, and connection management. The most important changes include adding URL validation, improving connection retry logic, and enhancing error messages.

Improvements to URL validation and connection handling:

• src/backend/base/langflow/base/mcp/util.py: Added validate_url method to validate SSE URLs before attempting connections and improved error handling in _connect_with_timeout and connect_to_server methods. [1] [2] [3] [4]

Enhancements to MCPToolsComponent:

• src/backend/base/langflow/components/tools/mcp_component.py: Added find_langflow_instance method to automatically detect Langflow instance and updated update_build_config and update_tools methods to use this detection for setting SSE URLs. [1] [2] [3] [4]

Additional changes:

• src/backend/base/langflow/base/mcp/util.py: Introduced constants for HTTP error status codes and added logging for better traceability. [1] [2]
• src/backend/base/langflow/components/tools/mcp_component.py: Improved type annotations and default values for class attributes. [1] [2]

[Copilot]

Pull Request Overview

This pull request enhances error handling and URL validation for MCP tools while making minor import adjustments in various test files. Key changes include:

• Implementation of URL validation, retry mechanisms, and improved logging for server connections.
• Addition of a new method to discover Langflow instances by scanning environment variables and common ports.
• Adjustments to import statements in several unit tests for consistency.

Reviewed Changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated no comments.

File	Description
src/backend/tests/unit/*.py	Minor import adjustments to ensure consistency
src/backend/base/langflow/components/tools/mcp_component.py	Added Langflow instance discovery method and enhanced SSE error handling
src/backend/base/langflow/base/mcp/util.py	Introduced URL validation and retry logic with improved error messages

Comments suppressed due to low confidence (1)

src/backend/base/langflow/components/tools/mcp_component.py:31

• [nitpick] Consider renaming 'default_keys' to 'DEFAULT_KEYS' to clearly indicate that it represents a constant configuration.

default_keys: list[str] = ["code", "_type", "mode", "command", "sse_url", "tool_placeholder", "tool_mode", "tool"]

[codspeed-hq]

CodSpeed Performance Report

Merging #7327 will improve performances by 40.11%

_{Comparing fix-mcp-tool-mode (6001734) with main (e82b23f)}

Summary

⚡ 2 improvements
✅ 17 untouched benchmarks

Benchmarks breakdown

	Benchmark	BASE	HEAD	Change
⚡	test_build_flow_invalid_job_id	12.4 ms	8.8 ms	+40.11%
⚡	test_cancel_nonexistent_build	12.2 ms	8.7 ms	+39.47%

[edwinjosechittilappilly]

@phact we might need to improve later for getting the base URL from the requests.

This PR is to improve the error handling as well as improve build config performance preventing further errors.