fix(mcp): wrap LoggingMiddleware.on_message event_logger in try/except by aminghadersohi · Pull Request #38560 · apache/superset

aminghadersohi · 2026-03-10T14:08:28Z

SUMMARY

After registering LoggingMiddleware in the MCP server startup, the MCP server started failing the initialize handshake with clients (e.g. Claude Code) with:

WARNING:root:Failed to validate request: Working outside of application context.

Root cause: LoggingMiddleware fires on ALL MCP messages including the protocol-level initialize handshake and the on_call_tool() finally block (which runs after mcp_auth_hook pops Flask context). Both on_message() and on_call_tool() call event_logger.log() which requires Flask app context, but:

During initialize there is no Flask app context (mcp_auth_hook only pushes context for tool calls, not protocol messages)
In on_call_tool()'s finally block, the Flask app context has already been popped by mcp_auth_hook

Fix: Use flask.has_app_context() guard check before event_logger.log() calls in both on_call_tool() and on_message(). This is explicit about intent, avoids exception-driven control flow, and won't accidentally swallow unrelated RuntimeErrors.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

N/A - backend fix

TESTING INSTRUCTIONS

Start the MCP server locally: superset mcp run --port 5008 --debug
Connect with an MCP client (e.g. Claude Code /mcp)
Verify the initialize handshake completes successfully (no Working outside of application context error)
Verify all 19 MCP tools work correctly (health_check, list_charts, list_dashboards, list_datasets, get_instance_info, get_schema, get_chart_info, get_dashboard_info, get_dataset_info, execute_sql, open_sql_lab_with_context, generate_explore_link, generate_chart, get_chart_data, get_chart_preview, update_chart, update_chart_preview, generate_dashboard, add_chart_to_existing_dashboard)
Verify tool calls still log properly via event_logger when Flask app context is available

ADDITIONAL INFORMATION

LoggingMiddleware.on_message() fires on all MCP messages including the initialize handshake, but event_logger.log() requires Flask app context which isn't available during protocol-level messages. This causes the MCP server to reject the initialize request with "Working outside of application context". Wrap the event_logger.log() call with try/except RuntimeError to gracefully skip logging when no Flask context is available.

bito-code-review · 2026-03-10T14:08:41Z

Code Review Agent Run #27be06

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Files reviewed - 1 · Commit Range: b30959d..b30959d
- superset/mcp_service/middleware.py
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codeant-ai-for-open-source · 2026-03-10T14:09:30Z

Sequence Diagram

This PR updates MCP message logging so that missing Flask application context during the initialize handshake no longer breaks the flow, allowing the handshake to succeed while still logging messages when context is available.

sequenceDiagram
    participant Client
    participant MCPServer
    participant Middleware
    participant EventLogger

    Client->>MCPServer: Send initialize message
    MCPServer->>Middleware: on_message with context
    Middleware->>EventLogger: Log MCP message

    alt Flask context available
        EventLogger-->>Middleware: Log entry recorded
    else No Flask context
        EventLogger-->>Middleware: RuntimeError raised
        Middleware->>Middleware: Catch error and skip logging
    end

    Middleware->>MCPServer: call_next and continue handling
    MCPServer-->>Client: Initialize response success

Generated by CodeAnt AI

…lask context The on_call_tool finally block runs event_logger.log() AFTER mcp_auth_hook pops the Flask app context, causing RuntimeError that destroys the successful tool result. Wrap all event_logger calls with try/except RuntimeError.

codecov · 2026-03-10T14:21:10Z

Codecov Report

❌ Patch coverage is 0% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 64.44%. Comparing base (bf55f1e) to head (ef63a81).
⚠️ Report is 26 commits behind head on master.

Files with missing lines	Patch %	Lines
superset/mcp_service/middleware.py	0.00%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #38560      +/-   ##
==========================================
- Coverage   64.85%   64.44%   -0.42%     
==========================================
  Files        1817     2529     +712     
  Lines       72183   128780   +56597     
  Branches    22975    29677    +6702     
==========================================
+ Hits        46815    82986   +36171     
- Misses      25368    44351   +18983     
- Partials        0     1443    +1443

Flag	Coverage Δ
hive	`40.80% <0.00%> (?)`
mysql	`61.97% <0.00%> (?)`
postgres	`62.04% <0.00%> (?)`
presto	`40.81% <0.00%> (?)`
python	`63.67% <0.00%> (?)`
sqlite	`61.67% <0.00%> (?)`
unit	`100.00% <ø> (?)`

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…ing-middleware-app-context

Replace exception-driven control flow with explicit Flask context check. This is cleaner because: - Explicit intent: only log when Flask context exists - Won't swallow unrelated RuntimeErrors - Avoids exception-driven control flow anti-pattern

bito-code-review · 2026-03-10T15:18:50Z

Code Review Agent Run #4e5e81

Actionable Suggestions - 0

Review Details

Files reviewed - 1 · Commit Range: b30959d..acbfcd6
- superset/mcp_service/middleware.py
Files skipped - 0
Tools
- Whispers (Secret Scanner) - ✔︎ Successful
- Detect-secrets (Secret Scanner) - ✔︎ Successful
- MyPy (Static Code Analysis) - ✔︎ Successful
- Astral Ruff (Static Code Analysis) - ✔︎ Successful

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…ing-middleware-app-context

apache#38560)

#38560) (cherry picked from commit 6d7cfac)

apache#38560) (cherry picked from commit 6d7cfac)

apache#38560)

pull-request-size bot added the size/M label Mar 10, 2026

codeant-ai-for-open-source bot added the size:S This PR changes 10-29 lines, ignoring generated files label Mar 10, 2026

dosubot bot added the change:backend Requires changing the backend label Mar 10, 2026

aminghadersohi added 3 commits March 10, 2026 10:43

chore: retrigger CI

cac8688

Merge remote-tracking branch 'upstream/master' into amin/fix-mcp-logg…

fb1d8ed

…ing-middleware-app-context

aminghadersohi added 2 commits March 10, 2026 11:28

Merge remote-tracking branch 'upstream/master' into amin/fix-mcp-logg…

c2a2a3e

…ing-middleware-app-context

chore: retrigger CI for flaky cypress download

9cda124

Antonio-RiveroMartnez approved these changes Mar 10, 2026

View reviewed changes

chore: retrigger CI (cypress download DNS flaky across repo)

ef63a81

kgabryje approved these changes Mar 10, 2026

View reviewed changes

Antonio-RiveroMartnez merged commit 6d7cfac into apache:master Mar 10, 2026
65 checks passed

bschreder pushed a commit to bschreder/superset that referenced this pull request Mar 11, 2026

fix(mcp): wrap LoggingMiddleware.on_message event_logger in try/except (

c2fca75

apache#38560)

michael-s-molina pushed a commit that referenced this pull request Mar 17, 2026

fix(mcp): wrap LoggingMiddleware.on_message event_logger in try/except (

a3dba46

#38560) (cherry picked from commit 6d7cfac)

aminghadersohi added a commit to aminghadersohi/superset that referenced this pull request Mar 17, 2026

fix(mcp): wrap LoggingMiddleware.on_message event_logger in try/except (

2c6a0de

apache#38560) (cherry picked from commit 6d7cfac)

MallikarjunaReddyN pushed a commit to MallikarjunaReddyN/superset that referenced this pull request Mar 18, 2026

fix(mcp): wrap LoggingMiddleware.on_message event_logger in try/except (

af20649

apache#38560)

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fix(mcp): wrap LoggingMiddleware.on_message event_logger in try/except#38560

fix(mcp): wrap LoggingMiddleware.on_message event_logger in try/except#38560
Antonio-RiveroMartnez merged 8 commits intoapache:masterfrom
aminghadersohi:amin/fix-mcp-logging-middleware-app-context

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aminghadersohi commented Mar 10, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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SUMMARY

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

TESTING INSTRUCTIONS

ADDITIONAL INFORMATION

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Sequence Diagram

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aminghadersohi commented Mar 10, 2026 •

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