Fix #1557: close MCP SSE connections before Tomcat graceful shutdown…

[igordayen]

Summary

Adds McpSseShutdownConfiguration to embabel-agent-mcpserver to fix a 30-second shutdown stall when using the MCP
server starter.

Closes: #1557

WebMvcSseServerTransportProvider keeps SSE connections open after MCP calls complete — by design, as SSE is a
persistent connection. On shutdown, Tomcat counts these as active requests and waits up to 30 seconds before
force-closing them. This fix listens for ContextClosedEvent (which fires before Tomcat's graceful shutdown phase) and
calls closeGracefully() to close all active sessions within a 5-second timeout.

Root cause

WebMvcSseServerTransportProvider.closeGracefully() exists in the MCP Java SDK but is not wired into the Spring
lifecycle by either the MCP Java SDK or Spring AI's autoconfiguration. The following upstream issues have been open
since late 2025 with no fix shipped:

• Spring AI #4002 — Tomcat cannot shut down after MCP client connects (open since Oct 2025, waiting-for-triage)
• MCP Java SDK Introduce AgentInvocation #635 — closeGracefully() can hang with no timeout (open, needs-repro)
• MCP Java SDK Issue-546 SPRING_ACTIVE_PROFILE was not getting added to the Environment #547 — closeGracefully() may leak resources (open, P2)

Versions affected: spring-ai-starter-mcp-server-webmvc 1.1.7 / MCP Java SDK 0.18.2.

Design notes

• @Autowired(required = false) is used instead of @ConditionalOnBean — the conditional evaluates before Spring AI
  registers the transport bean and always resolves to false. Optional injection defers the check until after all beans
  are created.
• closeGracefully() — safe to keep when upstream ships a fix, as a second call on an already-closed
  provider iterates an empty session map.
• 5-second timeout guards against the pipeline stalling (MCP Java SDK Introduce AgentInvocation #635).

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
93.3% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[igordayen]

@fctg-stevendoolan confirmed the fix is working properly.

[igordayen]

https://github.com/fctg-stevendoolan - please be aware of PR: #2071 , Mifration to Streamable HTTP.
Spring is removing a class used by McpSseShutdownConfiguration. Please consider switching from SSE to Streamable HTTP.
Thank you