fix(client): preserve resumption token when a resumed SSE stream drops before any id-bearing event - #2745
Open
ayush00git wants to merge 1 commit into
Conversation
…s before any id-bearing event Seed _handleSseStream's lastEventId tracker from the resumptionToken the stream was opened with, so a reconnect that saw no new events re-sends the same Last-Event-ID instead of dropping it. Fixes modelcontextprotocol#2499
🦋 Changeset detectedLatest commit: e01c0ae The changes in this PR will be included in the next version bump. This PR includes changesets to release 6 packages
Not sure what this means? Click here to learn what changesets are. Click here if you're a maintainer who wants to add another changeset to this PR |
@modelcontextprotocol/client
@modelcontextprotocol/codemod
@modelcontextprotocol/core
@modelcontextprotocol/server
@modelcontextprotocol/server-legacy
@modelcontextprotocol/express
@modelcontextprotocol/fastify
@modelcontextprotocol/hono
@modelcontextprotocol/node
commit: |
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
1 participant
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Fixes #2499
What the error was
In
StreamableHTTPClientTransport,_handleSseStream()keeps track of the latest SSE event id in a locallastEventIdthat starts out asundefined. It was never seeded from theresumptionTokenthe stream was opened with, but both reconnect paths (graceful close and network error) pass that local along as the token for the next attempt.So if a stream resumed with
Last-Event-ID: e1got cut again before the server replayed any id-bearing event (load balancer idle timeout, server restart), the reconnect GET went out with noLast-Event-IDheader at all. The server saw a brand-new stream, the missed events were never replayed, and a long-running request just hung until it timed out.How this PR fixes it
lastEventIdis now initialised fromoptions.resumptionToken. A reconnect that saw no new events re-sends the same cursor, which is safe because replay from an already-seen id is idempotent. Once a newer event id arrives it overrides the seed as before.onresumptiontokenbehaviour is unchanged: it still only fires for ids actually received on the wire, not for the seed.Added three regression tests under
Reconnection Logic:Last-Event-IDonresumptiontokenThe first two fail on
mainand pass with this change. Also added a patch changeset for@modelcontextprotocol/client.