streamable session persists past client disconnect

[jba]

StreamableHTTPHandler holds a map of StreamableServerTransports. Currently, an entry from that map is freed only when the client sends a DELETE. We should also free it when the client stops responding to keepalive pings. If clients don't send DELETEs, the server memory will grow without bound.

[findleyr]

IMO this should be an implementation detail of the session store. The memory store should have an eviction policy.

[jba]

TCP connections don't have an eviction policy; they stay open until the peer explicitly closes them or keepalive fails. I don't see why we shouldn't do the same. You should be able to walk away from your machine that has an MCP client, come back the next day, and continue work.

[findleyr]

@h9jiang this might be something you could pick up.

[samthanawalla]

Duplicate of #190 ?

[h9jiang]

@samthanawalla This focus on the unbounded map

type StreamableHTTPHandler struct {
  transports map[string]*StreamableServerTransport // keyed by IDs (from Mcp-Session-Id header)
}

and should fix by deleting the map entry once keep alive failed.

Need @jba for confirmation.

[jba]

@h9jiang that is correct, but it may not be sufficient. Is there anything else in a StreamableServerTransport that needs to be shut down before it dropped? If it has a Close method, that should be called, probably.