What does this PR do?
Fixes error handling when MCP server connections fail. Instead of
returning generic 500 errors, now provides
descriptive error messages with proper HTTP status codes.
Closes#3107
Test Plan
Before fix:
curl -X GET
"http://localhost:8321/v1/tool-runtime/list-tools?tool_group_id=bad-mcp-server"
Returns: {"detail": "Internal server error: An unexpected error
occurred."} (500)
After fix:
curl -X GET
"http://localhost:8321/v1/tool-runtime/list-tools?tool_group_id=bad-mcp-server"
Returns: {"error": {"detail": "Failed to connect to MCP server at
http://localhost:9999/sse: Connection
refused"}} (502)
Tests:
- Added unit test for ConnectionError → 502 translation
- Manually tested with unreachable MCP servers (connection refused)
Resolves access control error visibility issues where 500 errors were
returned instead of proper 403 responses with actionable error messages.
• Enhance AccessDeniedError with detailed context and improve exception
handling
• Enhanced AccessDeniedError class to include user, action, and resource
context
- Added constructor parameters for action, resource, and user
- Generate detailed error messages showing user principal, attributes,
and attempted resource
- Backward compatible with existing usage (falls back to generic
message)
• Updated exception handling in server.py
- Import AccessDeniedError from access_control module
- Return proper 403 status codes with detailed error messages
- Separate handling for PermissionError (generic) vs AccessDeniedError
(detailed)
• Enhanced error context at raise sites
- Updated routing_tables/common.py to pass action, resource, and user
context
- Updated agents persistence to include context in access denied errors
- Provides better debugging information for access control issues
• Added comprehensive unit tests
- Created tests/unit/server/test_server.py with 13 test cases
- Covers AccessDeniedError with and without context
- Tests all exception types (ValidationError, BadRequestError,
AuthenticationRequiredError, etc.)
- Validates proper HTTP status codes and error message formats
# What does this PR do?
<!-- Provide a short summary of what this PR does and why. Link to
relevant issues if applicable. -->
<!-- If resolving an issue, uncomment and update the line below -->
<!-- Closes #[issue-number] -->
## Test Plan
```
server:
port: 8321
access_policy:
- permit:
principal: admin
actions: [create, read, delete]
when: user with admin in groups
- permit:
actions: [read]
when: user with system:authenticated in roles
```
then:
```
curl --request POST --url http://localhost:8321/v1/vector-dbs \
--header "Authorization: Bearer your-bearer" \
--data '{
"vector_db_id": "my_demo_vector_db",
"embedding_model": "ibm-granite/granite-embedding-125m-english",
"embedding_dimension": 768,
"provider_id": "milvus"
}'
```
depending if user is in group admin or not, you should get the
`AccessDeniedError`. Before this PR, this was leading to an error 500
and `Traceback` displayed in the logs.
After the PR, logs display a simpler error (unless DEBUG logging is set)
and a 403 Forbidden error is returned on the HTTP side.
---------
Signed-off-by: Akram Ben Aissi <<akram.benaissi@gmail.com>>
