fix: clean up benchmark MCP sessions #94
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,104 @@ | ||
| import process from 'node:process'; | ||
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| async function loadSdkClient() { | ||
| const [{ Client }, { StdioClientTransport }] = await Promise.all([ | ||
| import('@modelcontextprotocol/sdk/client/index.js'), | ||
| import('@modelcontextprotocol/sdk/client/stdio.js') | ||
| ]); | ||
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| return { Client, StdioClientTransport }; | ||
| } | ||
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| function createTimeoutError(timeoutMs) { | ||
| const seconds = Math.max(1, Math.round(timeoutMs / 1000)); | ||
| return new Error(`MCP client connect timed out after ${seconds}s`); | ||
| } | ||
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| function withTimeout(promise, timeoutMs) { | ||
| if (!Number.isFinite(timeoutMs) || timeoutMs <= 0) { | ||
| return promise; | ||
| } | ||
|
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| let timer; | ||
| const timeoutPromise = new Promise((_, reject) => { | ||
| timer = setTimeout(() => reject(createTimeoutError(timeoutMs)), timeoutMs); | ||
| timer.unref?.(); | ||
| }); | ||
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| return Promise.race([promise, timeoutPromise]).finally(() => { | ||
| if (timer) { | ||
| clearTimeout(timer); | ||
| } | ||
| }); | ||
| } | ||
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| function delay(timeoutMs) { | ||
| return new Promise((resolve) => { | ||
| const timer = setTimeout(resolve, timeoutMs); | ||
| timer.unref?.(); | ||
| }); | ||
| } | ||
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| async function safeClose(client, transport, connected) { | ||
| const closeAttempts = []; | ||
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| if (connected) { | ||
| closeAttempts.push(client.close().catch(() => undefined)); | ||
| } | ||
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| closeAttempts.push(transport.close?.().catch(() => undefined)); | ||
| await Promise.all(closeAttempts); | ||
| } | ||
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| export async function withManagedStdioClientSession(options, callback) { | ||
| const { | ||
| serverCommand, | ||
| serverArgs = [], | ||
| serverEnv = {}, | ||
| cwd, | ||
| clientInfo = { name: 'benchmark-runner', version: '1.0.0' }, | ||
| connectTimeoutMs = 10_000, | ||
| onSpawn | ||
| } = options; | ||
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| const { Client, StdioClientTransport } = await loadSdkClient(); | ||
| const transport = new StdioClientTransport({ | ||
| command: serverCommand, | ||
| args: serverArgs, | ||
| env: { ...process.env, ...serverEnv }, | ||
| cwd | ||
| }); | ||
| const client = new Client(clientInfo); | ||
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| let connected = false; | ||
| let settling = false; | ||
| const connectPromise = client.connect(transport); | ||
| const spawnNotification = (async () => { | ||
| if (typeof onSpawn !== 'function') { | ||
| return; | ||
| } | ||
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| while (!settling) { | ||
| if (transport.pid !== null) { | ||
| onSpawn(transport.pid); | ||
| return; | ||
| } | ||
| await new Promise((resolve) => setTimeout(resolve, 10)); | ||
| } | ||
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| if (transport.pid !== null) { | ||
| onSpawn(transport.pid); | ||
| } | ||
| })(); | ||
|
Comment on lines
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Contributor
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The polling loop exits the moment In practice, with a 200 ms timeout and a local process that spawns in < 50 ms, the window is very narrow. But under CI load or on slow machines the test can become flaky. A robust fix is to perform one final pid check after the loop exits: const spawnNotification = (async () => {
if (typeof onSpawn !== 'function') return;
while (!settling) {
if (transport.pid !== null) {
onSpawn(transport.pid);
return;
}
await new Promise((resolve) => setTimeout(resolve, 10));
}
// One final check: process may have spawned while we were asleep
if (transport.pid !== null) {
onSpawn(transport.pid);
}
})(); |
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| try { | ||
| await withTimeout(connectPromise, connectTimeoutMs); | ||
| connected = true; | ||
| return await callback({ client, transport }); | ||
| } finally { | ||
| settling = true; | ||
| await safeClose(client, transport, connected); | ||
| await spawnNotification.catch(() => undefined); | ||
| await Promise.race([connectPromise, delay(5_000)]).catch(() => undefined); | ||
| } | ||
| } | ||
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err.message.startsWith('Failed to connect to')can never be true here.withManagedStdioClientSessioneither throws"MCP client connect timed out after Xs"(timeout path) or re-throws errors from the callback, none of which start with"Failed to connect to". The guard is harmless but misleading; removing it makes the intent clearer: