Fix #45: Add MCPConnectionErrorFilter for cleaner production logs

[Mr-Neutr0n]

Fixes #45

Added MCPConnectionErrorFilter class (downgrades expected disconnect patterns to DEBUG) and ENABLE_MCP_CONNECTION_FILTER feature flag (default True), wired into the app lifespan, applied to mcp, uvicorn.error, and starlette loggers, with tests and docs.

Local test infra unavailable in CI sandbox.

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This change was prepared with AI assistance under human direction and review.

Summary by CodeRabbit

• New Features

  • Added an environment setting to control filtering of expected MCP connection errors.
  • Expected disconnect, reset, and broken-pipe errors are now reduced from ERROR to DEBUG logs by default, minimizing log noise.
  • Filtering can be disabled through configuration when full error logging is needed.

• Documentation

  • Documented the new configuration option and its default behavior in the development guide.

[coderabbitai]

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

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Run ID: ef18f564-8b64-487b-8cb4-eed64f2655d2

📥 Commits

Reviewing files that changed from the base of the PR and between 7112f47 and 49c6d68.

📒 Files selected for processing (6)

• .env.example
• docs/development.md
• template_mcp_server/src/api.py
• template_mcp_server/src/settings.py
• template_mcp_server/utils/pylogger.py
• tests/test_utils.py

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📝 Walkthrough

Walkthrough

Adds a default-enabled configuration flag and logging filter that downgrades expected MCP disconnect, reset, and broken-pipe errors to DEBUG. The filter is attached during application startup to MCP-related loggers and covered by unit tests.

Changes

MCP connection error filtering

Layer / File(s)	Summary
Filtering configuration contract .env.example, template_mcp_server/src/settings.py, docs/development.md	Adds ENABLE_MCP_CONNECTION_FILTER, defaulting to True, with documentation describing the filtered connection errors.
Filter behavior and validation template_mcp_server/utils/pylogger.py, tests/test_utils.py	Adds case-insensitive matching for expected connection error patterns, downgrades matches to DEBUG, preserves unrelated errors, and tests the behavior.
Application startup wiring template_mcp_server/src/api.py, template_mcp_server/utils/pylogger.py, tests/test_utils.py	Attaches the filter to mcp, uvicorn.error, and starlette during lifespan startup, with enabled and disabled attachment tests.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Sequence Diagram(s)

sequenceDiagram
  participant FastAPI lifespan
  participant Logging setup
  participant MCP loggers
  FastAPI lifespan->>Logging setup: pass ENABLE_MCP_CONNECTION_FILTER
  Logging setup->>MCP loggers: attach MCPConnectionErrorFilter when enabled
  MCP loggers->>MCP loggers: downgrade expected connection errors to DEBUG

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🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly matches the main change: adding MCPConnectionErrorFilter to reduce production log noise.
Linked Issues check	✅ Passed	The PR appears to meet #45 by adding the feature flag, filter behavior, logger attachment, tests, and docs.
Out of Scope Changes check	✅ Passed	The changes stay focused on MCP logging cleanup, configuration, docs, and tests with no obvious unrelated scope.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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