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Title: Evict streamable HTTP sessions after failed keep-alive pings by lxq19991111 · Pull Request #1028 · modelcontextprotocol/java-sdk · GitHub

Open Graph Title: Evict streamable HTTP sessions after failed keep-alive pings by lxq19991111 · Pull Request #1028 · modelcontextprotocol/java-sdk

X Title: Evict streamable HTTP sessions after failed keep-alive pings by lxq19991111 · Pull Request #1028 · modelcontextprotocol/java-sdk

Description: Summary Fixes #1022. Evict dead Streamable HTTP sessions after repeated keep-alive ping failures. When keep-alive-interval is enabled, KeepAliveScheduler currently detects dead sessions by logging failed pings, but the failed sessions remain in the Streamable HTTP provider's session registry. Over time, the scheduler keeps pinging the same unreachable sessions every interval, causing repeated WARN logs and CPU usage that grows with the number of accumulated dead sessions. This PR adds keep-alive success/failure hooks and lets the Streamable HTTP servlet provider evict the logical session after consecutive keep-alive failures. Dependency / Review Order Depends on #1027. #1027 establishes the transport-level lifecycle behavior: servlet async lifecycle events and SSE write failures close only the current HTTP/SSE transport while keeping the logical MCP session registered. This PR builds on that behavior by evicting the logical MCP session only after repeated keep-alive ping failures. After #1027 lands, this PR should be rebased on top of it so the keep-alive eviction behavior does not conflict with transport-level write-failure cleanup. Related Issues and PRs Fixes #1022. Depends on #1027 for servlet async lifecycle cleanup and write-failure semantics. Related to #952 and #972: this PR should not be interpreted as deleting the logical session on a single request-specific write failure. That behavior belongs to #1027 / #972. Related to #920: transient write failures should not immediately orphan a session, so this PR uses a consecutive-failure threshold rather than evicting on the first failure. Changes Add success and failure callbacks to KeepAliveScheduler. Keep the new scheduler callbacks backward compatible by defaulting them to no-op handlers. Track consecutive keep-alive ping failures in HttpServletStreamableServerTransportProvider. Reset the failure count after a successful keep-alive ping. Evict and close a Streamable HTTP session after 3 consecutive keep-alive ping failures. Clear failure counts on session deletion and provider shutdown. Guard failure-count reset and eviction with session identity checks so stale keep-alive results cannot affect a replaced session. Add focused tests for scheduler callbacks and Streamable HTTP keep-alive eviction behavior. Rationale The issue suggested doing the failure counter and session removal directly in KeepAliveScheduler. This PR intentionally keeps KeepAliveScheduler transport-agnostic. KeepAliveScheduler only receives a Supplier>. It does not own the Streamable HTTP provider's session registry, and it cannot safely remove entries from that registry directly. The Streamable HTTP servlet provider owns the sessions map, so it also owns eviction. The scheduler reports ping success or failure through hooks, and the provider decides whether to reset the failure count, keep the session, or evict it. This PR also avoids evicting on the first failure. A single failed ping can be transient, especially around load balancer timeouts, reconnects, request-specific streams, or temporary transport unavailability. Requiring 3 consecutive failures provides a conservative boundary between transient transport failure and a logical session that is no longer reachable. Session TTL is intentionally left out of this PR. TTL may still be useful as a separate defense-in-depth policy, but this PR focuses only on sessions that keep-alive has already identified as repeatedly unreachable. Scope This PR intentionally focuses on: KeepAliveScheduler Streamable HTTP servlet session eviction in HttpServletStreamableServerTransportProvider Out of scope: Servlet async lifecycle cleanup and write-failure retention, handled in #1027 Explicit session TTL Configurable keep-alive failure threshold Session persistence / distributed session storage Last-Event-ID resumability / event store support Deprecated HttpServletSseServerTransportProvider How Has This Been Tested? mvn -pl mcp-core -Dtest=KeepAliveSchedulerTests,HttpServletStreamableServerTransportProviderTests test mvn -pl mcp-core test The added scheduler tests cover: null success/failure callback validation success callback invocation after successful ping failure callback invocation after failed ping callback exceptions do not stop the scheduler The added provider tests cover: first keep-alive failure does not evict the session repeated keep-alive failures evict and close the session successful keep-alive resets the failure count stale failures from an old session instance do not evict a replacement session with the same id Types of changes Bug fix (non-breaking change which fixes an issue) New feature (non-breaking change which adds functionality) Breaking change (fix or feature that would cause existing functionality to change) Documentation update Checklist I have read the MCP Documentation My code follows the repository's style guidelines New and existing tests pass locally I have added appropriate error handling I have added or updated documentation as needed

Open Graph Description: Summary Fixes #1022. Evict dead Streamable HTTP sessions after repeated keep-alive ping failures. When keep-alive-interval is enabled, KeepAliveScheduler currently detects dead sessions by logging ...

X Description: Summary Fixes #1022. Evict dead Streamable HTTP sessions after repeated keep-alive ping failures. When keep-alive-interval is enabled, KeepAliveScheduler currently detects dead sessions by logging ...

Opengraph URL: https://github.com/modelcontextprotocol/java-sdk/pull/1028

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