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[Server] Make subscriptions/listen actually deliver (#451)

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The stream acknowledged, slept thirty seconds and closed, so tools and
resource changes never reached a client — and with resources/subscribe
gone, that left the revision with no server-push at all. A notification bus
carries them: in-memory where publisher and stream share a process, PSR-16
where php-fpm puts them in different ones. The conformance server proves
the latter — a tools/call in one worker reaches a stream held in another.
This commit is contained in:
Christopher Hertel 2026-08-19 00:08:02 +02:00 • committed by GitHub
commit daac88d626
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1 changed files with 907 additions and 13 deletions
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59
src/Server/Stateless/StatelessProtocol.php
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@ -31,6 +31,7 @@ use Mcp\Server\Handler\Request\RequestHandlerInterface;
use Mcp\Server\Protocol;
use Mcp\Server\Session\InMemorySessionStore;
use Mcp\Server\Session\Session;
use Mcp\Server\Subscription\NotificationBusInterface;
use Mcp\Server\Wire\CachePolicy;
use Mcp\Server\Wire\Rev2026Codec;
use Mcp\Server\Wire\WireCodecInterface;
@ -100,6 +101,7 @@ final class StatelessProtocol
private readonly ?StandardHeaderValidator $headerValidator = null,
private readonly ?RequestStateCodec $requestStateCodec = null,
?CachePolicy $cachePolicy = null,
private readonly ?NotificationBusInterface $notificationBus = null,
) {
$this->codec = $codec ?? new Rev2026Codec($configuration->serverInfo, $cachePolicy);
@ -295,8 +297,12 @@ final class StatelessProtocol
$agreed = NotificationFilter::fromParams($notifications)->intersect($this->configuration->capabilities);
$lifetime = $this->subscriptionLifetime;
$bus = $this->notificationBus;
$codec = $this->codec;
return StatelessResult::stream(static function () use ($agreed, $id, $lifetime): \Generator {
return StatelessResult::stream(static function () use ($agreed, $id, $lifetime, $bus, $codec): \Generator {
// MUST be the first message carrying this subscription's id, and
// MUST precede any notification on it.
yield [
'jsonrpc' => '2.0',
'method' => self::ACKNOWLEDGED_NOTIFICATION,
@ -306,12 +312,27 @@ final class StatelessProtocol
],
];
// Cross-request notifications need a channel this SDK does not
// define yet, so the stream only waits. The tick is not optional:
// PHP spots a dropped peer by writing, and a sleeping loop would
// pin an FPM worker for the full lifetime.
$deadline = microtime(true) + $lifetime;
// From now, not from the beginning: a subscriber wants what happens
// next, not a replay of the server's history.
$cursor = $bus?->cursor() ?? 0;
// The tick is not optional: PHP spots a dropped peer by writing,
// and a sleeping loop would pin an FPM worker for the full lifetime.
$deadline = 0.0 >= $lifetime ? \INF : microtime(true) + $lifetime;
while (microtime(true) < $deadline) {
if (null !== $bus) {
[$notifications, $cursor] = $bus->since($cursor);
foreach ($notifications as $notification) {
if (!$agreed->carries($notification)) {
continue;
}
yield self::tagWithSubscription($notification, $id);
}
}
yield null;
if (connection_aborted()) {
@ -326,14 +347,36 @@ final class StatelessProtocol
yield [
'jsonrpc' => '2.0',
'id' => $id,
'result' => [
'result' => $codec->encodeResult(self::LISTEN_METHOD, [
'resultType' => 'complete',
'_meta' => [RequestMeta::SUBSCRIPTION_ID => $id],
],
], false),
];
});
}
/**
* Every message on a listen stream carries the id of the subscription it
* belongs to, which is how a client demultiplexes them on stdio — where
* they all share one channel.
*
* @return array<string, mixed>
*/
private static function tagWithSubscription(Notification $notification, string|int $id): array
{
/** @var array<string, mixed> $frame */
$frame = $notification->jsonSerialize();
$params = \is_array($frame['params'] ?? null) ? $frame['params'] : [];
$meta = \is_array($params['_meta'] ?? null) ? $params['_meta'] : [];
$meta[RequestMeta::SUBSCRIPTION_ID] = $id;
$params['_meta'] = $meta;
$frame['params'] = $params;
return $frame;
}
private function discover(): DiscoverResult
{
return new DiscoverResult(