[Jetty] Notified a stream only while a reader armed it.

crates/protos/protos/local/temporal/sdk/core/streams/streams.proto

@@ -40,11 +40,12 @@ message StreamStoreConfig {
     RedisStoreConfig redis = 1;
     MemoryStoreConfig memory = 2;
   }
-  // Tells each stream's notifier on the server when the stream moves, after every append. That's
-  // what wakes a reader that waits on the notifier. Off by default, since most streams have no such
-  // reader and each notification costs a call. It turns on progress only. Closes reach the
-  // notifier either way. A server without the stream notifier costs one call, and then the process
-  // stops notifying.
+  // Tells each stream's notifier on the server when the stream moves while a reader sleeps on
+  // it: after an append, when a reader armed the stream with an empty read. That's what wakes a
+  // reader that waits on the notifier. A busy stream, whose readers find records on each read,
+  // costs no notification. Off by default, since most streams have no such reader. It turns on
+  // progress only. Closes reach the notifier either way. A server without the stream notifier
+  // costs one call, and then the process stops notifying.
   bool notify_on_append = 3;
   // How many streams to keep a notifier for, dropping the least recently used. Zero uses 1000.
   uint32 max_notifiers = 4;

crates/streams/src/lib.rs

@@ -28,7 +28,7 @@ pub use error::{StreamError, StreamResult};
 pub use handle::{OWNER_RECHECK, OWNER_START_GRACE, Streams, StreamsOptions};
 pub use memory::MemoryStore;
 pub use notify::{
-    CLOSE_RETRY_CAP, CLOSE_RETRY_FIRST, CLOSE_RETRY_LIMIT, DEFAULT_MAX_NOTIFIERS, FLUSH_LIMIT,
+    Arm, CLOSE_RETRY_CAP, CLOSE_RETRY_FIRST, CLOSE_RETRY_LIMIT, DEFAULT_MAX_NOTIFIERS, FLUSH_LIMIT,
     Notifier, NotifierClient, NotifyError, NotifyingStore, StreamNotification, progress_counter,
 };
 pub use owner::{OwnerClient, OwnerDescription, OwnerError};