STAC MCP Server

--- title: "ADR 0007 Implementation Summary" status: completed date: 2025-01-07 branch: copilot/improve-client-configuration related_adr: architecture/0007-client-config-and-error-handling.md --- # ADR 0007 – Implementation Summary This addendum records the concrete work that delivered ADR 0007 (Client Configuration and Error Handling). It complements the architectural decision by documenting the shipped behaviour, test coverage, and follow-up ideas. ## Snapshot - **Primary module:** `stac_mcp/tools/client.py` - **Supporting docs/tests:** - `README.md` (client configuration section) - `tests/test_client_config_and_errors.py` - `tests/test_client_configuration_integration.py` - `examples/client_config_example.py` ## Key Technical Outcomes ### Configurable HTTP calls - `_http_json()` now accepts optional `timeout` and `headers` arguments that merge with instance defaults. - Timeouts propagate across retries to guarantee consistent behaviour. ### Resilient networking - Added `STACTimeoutError` and `ConnectionFailedError` for precise error handling. - `_map_connection_error()` translates `URLError` reasons into actionable remediation guidance. - Automatic retry loop (3 attempts, exponential back-off starting at 0.2 s) covers transient network faults. ### Logging discipline - Network failures log at `ERROR` level without stack traces, avoiding stderr noise while retaining context. - Successful calls remain silent; stdout is untouched to preserve MCP protocol streams. ### Backward compatibility - Default runtime behaviour (30 s timeout, minimal headers) is unchanged for existing consumers. - 404 responses still return `None`; non-404 HTTP errors re-raise immediately. ## Test Coverage | Suite | Focus | Notes | |-------|-------|-------| | `tests/test_client_config_and_errors.py` | Unit coverage for timeout/header merging, error mapping, logging behaviour, retries | 18 tests across timeout, header, error mapping, logging, and compatibility scenarios | | `tests/test_client_configuration_integration.py` | End-to-end validation of ADR 0007 behaviours | 14 tests covering success paths, retry semantics, logging expectations, and edge cases | Example invocation: ```bash pytest tests/test_client_config_and_errors.py tests/test_client_configuration_integration.py -v ``` ## Developer Experience - Example script (`examples/client_config_example.py`) demonstrates typical configurations and error handling patterns. - README section “Client Configuration (ADR 0007)” walks through per-call settings, retries, and failure modes with copyable snippets. ## Benefits by Persona - **Users:** receive clear, actionable network error messages and can tune timeouts/headers without code forks. - **Agents/Automation:** can branch on concrete exception classes, leading to smarter retries or escalations. - **Maintainers:** gain deterministic tests, comprehensive documentation, and zero breaking changes for legacy integrations. ## Follow-up Opportunities 1. **Environment-sourced defaults** (see ADR 0010) for timeout/header overrides. 2. **Observability hooks** (ADR 0012) to capture timeout vs. connection failure metrics. 3. **Circuit breaker guards** to temporarily suppress repeatedly failing catalog calls. 4. **Per-catalog configuration registry** for multi-tenant deployments. ## Validation Checklist - [x] Unit tests: `pytest tests/test_client_config_and_errors.py -v` - [x] Integration tests: `pytest tests/test_client_configuration_integration.py -v` - [x] Example run: `python examples/client_config_example.py` ## Change Log (key commits) 1. `62ffcf1` — implement timeout/header configuration and error mapping. 2. `249b116` — document ADR 0007 behaviour in README and helper docs. 3. `1fa117d` — add comprehensive examples and integration tests. ## Conclusion ADR 0007 is fully realised: configurable HTTP behaviour, resilient error handling, actionable logging, and thorough regression coverage ship together while maintaining compatibility with earlier releases.