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handleAutomaticTaskPolling ignores AbortSignal; cancelled requests poll indefinitely #2018
Description
Initial Checks
- Using the latest version of MCP TypeScript SDK
- Searched existing issues
Description
In packages/server/src/server/mcp.ts, handleAutomaticTaskPolling contains a while loop (lines 328-335) that polls a task store until completion. The loop never checks ctx.mcpReq.signal.aborted. If the client cancels the request, the poll loop continues consuming server resources indefinitely.
while (task.status !== 'completed' && task.status !== 'failed' && task.status !== 'cancelled') {
await new Promise(resolve => setTimeout(resolve, pollInterval));
const updatedTask = await ctx.task.store.getTask(taskId);
// ...
}The taskManager.ts implementation of the same pattern correctly checks the signal (line 856):
if (signal.aborted) {
resolver(new ProtocolError(ProtocolErrorCode.InternalError, 'Task cancelled or completed'));
break;
}Impact
On multi-tenant servers, a single cancelled long-running tool leaks a polling loop per cancelled request. Over time this accumulates.
Suggested fix
while (task.status !== 'completed' && task.status !== 'failed' && task.status !== 'cancelled') {
if (ctx.mcpReq.signal.aborted) {
throw new ProtocolError(ProtocolErrorCode.RequestCancelled, 'Request cancelled during task polling');
}
await new Promise(resolve => setTimeout(resolve, pollInterval));
// ...
}
Activity