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[Server] Add Psr6SessionStore and Psr6NotificationBus - #635
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chr-hertel merged 1 commit intoOct 28, 2026
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nicolas-grekas
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October 27, 2026 21:23
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🟡 Changes recommended
Cursor expiry can reset the sequence in both notification buses, causing listeners to silently miss newly published notifications.
1 open issue
What changed in this PR
Adds direct PSR-6 cache support to the SDK’s session storage, notification bus, and discovery caching, allowing integrations to use cache pools without a PSR-16 wrapper.
Changes:
- Introduces
Psr6SessionStoreandPsr6NotificationBusalongside their PSR-16 counterparts. - Extends discovery caching to accept PSR-6 pools.
- Adds tests and updates documentation, examples, and the changelog.
| File | Description |
|---|---|
| tests/Unit/Server/Subscription/NotificationBusTest.php | Adds PSR-6 coverage and shared backlog tests. |
| tests/Unit/Server/Session/SessionTest.php | Includes PSR-6 in shared session tests. |
| tests/Unit/Server/Session/Psr6SessionStoreTest.php | Tests failures, TTL, and PSR-16 session compatibility. |
| tests/Unit/Capability/Discovery/CachedDiscovererTest.php | Tests PSR-6 discovery caching and clearing. |
| src/Server/Subscription/Psr6NotificationBus.php | Adds a PSR-6 notification bus. |
| src/Server/Subscription/InMemoryNotificationBus.php | Documents the PSR-6 alternative. |
| src/Server/Session/Psr6SessionStore.php | Adds PSR-6 session storage. |
| src/Server/Builder.php | Accepts PSR-6 discovery pools and documents the new bus. |
| src/Capability/Discovery/CachedDiscoverer.php | Supports PSR-6 cache reads and writes. |
| examples/server/stateless-lifecycle/server.php | Updates comments to mention the PSR-6 bus. |
| docs/run/subscriptions.md | Shows PSR-6 notification bus configuration. |
| docs/run/sessions.md | Documents PSR-6 storage and Redis examples. |
| docs/run/server-builder.md | Updates discovery types and cache examples. |
| docs/get-started/installation.md | Lists PSR-6 cache implementation options. |
| CHANGELOG.md | Records the new PSR-6 support. |
Review effort: Balanced
| { | ||
| $item = $this->cache->getItem($this->key($suffix)); | ||
|
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| $this->cache->save($item->set($value)->expiresAfter($this->ttl)); |
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Fixed in 53d28ee, in both buses: the counter has no TTL anymore, and a reader whose cursor is ahead of a counter that got lost (evicted or cleared) reads what the bus holds.
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They work like their PSR-16 siblings over a PSR-6 cache pool. `Builder::setDiscovery()` also accepts a PSR-6 pool. The sequence counter of `Psr16NotificationBus` no longer expires, so that its subscribers do not miss the notifications published after a quiet period. Both notification buses read their backlog with one `getMultiple()` or `getItems()` call, not one call per entry.
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chr-hertel
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| $this->cache->set($this->key((string) $sequence), json_encode($notification, \JSON_THROW_ON_ERROR), $this->ttl); | ||
| $this->cache->set($this->key(self::CURSOR_KEY), $sequence + 1, $this->ttl); | ||
| // No TTL, so that the cursors of subscribers stay valid when the bus goes quiet | ||
| $this->cache->set($this->key(self::CURSOR_KEY), $sequence + 1); |
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did you run into an issue with the ttl - maybe 120 is just too short? not sure about not having one at all
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As discussed in symfony/ai#2853: the Symfony MCP Bundle wraps
cache.app, a PSR-6 pool, inPsr16Cacheto usePsr16SessionStoreandPsr16NotificationBus. That's the only reason it requirespsr/simple-cache. With these two classes, the bundle can use the pool directly.Psr6SessionStoreandPsr6NotificationBustake the same arguments as their PSR-16 siblings and use the same keys. With symfony/cache, a session written byPsr16SessionStorethroughPsr16Cachecan be read byPsr6SessionStorefrom the pool, so apps keep their sessions when they switch.Unlike
Psr16SessionStore,Psr6SessionStorecatches no exception: PSR-6 doesn't allow pools to throw anything butInvalidArgumentExceptionfor an invalid key, while PSR-16 has no such rule.Builder::setDiscovery()also accepts a PSR-6 pool, since that's a few lines inCachedDiscoverer.It also fixes
Psr16NotificationBusstarting its sequence over after being quiet for longer than its TTL, which made subscribers miss the next notifications (spotted by the review below).Both notification buses read their backlog with one
getMultiple()orgetItems()call, not one call per entry.