From 158e39760b00bc8db649fa0943949246462322ba Mon Sep 17 00:00:00 2001
From: michael <mn.nekrashevich@yandex.ru>
Date: Fri, 4 Sep 2026 21:47:41 +0300
Subject: [PATCH] Core: invoke ready watcher even if discovery fails

In async transport initialization (buildAsync) the ready watcher was
never called when discovery failed: YdbDiscovery.waitReady throws
IllegalStateException and the exception was swallowed by the executor,
so the caller waited forever.

Wrap waitReady in try/catch/finally so readyWatcher.run() is always
executed, and log the discovery failure with its cause.

Fixes #294
---
 CHANGELOG.md                                  |  3 ++
 .../tech/ydb/core/impl/YdbTransportImpl.java  |  9 ++++--
 .../ydb/core/impl/YdbTransportImplTest.java   | 28 +++++++++++++++++++
 3 files changed, 38 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index e2c213392..84a62a8e7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,6 @@
+## 2.4.12 ##
+* Core: fixed ready watcher invocation on discovery error
+
 ## 2.4.11 ##
 * Table: fixed StackOverflow problem for the immediately released sessions
 
diff --git a/core/src/main/java/tech/ydb/core/impl/YdbTransportImpl.java b/core/src/main/java/tech/ydb/core/impl/YdbTransportImpl.java
index d0d8e1e4d..e3a38f3a8 100644
--- a/core/src/main/java/tech/ydb/core/impl/YdbTransportImpl.java
+++ b/core/src/main/java/tech/ydb/core/impl/YdbTransportImpl.java
@@ -83,8 +83,13 @@ public void startAsync(Runnable readyWatcher) {
         discovery.start();
         if (readyWatcher != null) {
             scheduler.execute(() -> {
-                discovery.waitReady(-1);
-                readyWatcher.run();
+                try {
+                    discovery.waitReady(-1);
+                } catch (RuntimeException ex) {
+                    logger.warn("Discovery failed during async transport initialization", ex);
+                } finally {
+                    readyWatcher.run();
+                }
             });
         }
     }
diff --git a/core/src/test/java/tech/ydb/core/impl/YdbTransportImplTest.java b/core/src/test/java/tech/ydb/core/impl/YdbTransportImplTest.java
index e5fc1c5ab..5978a3988 100644
--- a/core/src/test/java/tech/ydb/core/impl/YdbTransportImplTest.java
+++ b/core/src/test/java/tech/ydb/core/impl/YdbTransportImplTest.java
@@ -186,6 +186,34 @@ public void asyncBuildGoodTest() {
         Assert.assertTrue(isReady.isDone());
     }
 
+    @Test
+    public void asyncBuildDiscoveryErrorTest() {
+        MockedScheduler scheduler = new MockedScheduler(MockedClock.create(ZoneId.of("UTC")));
+
+        Mockito.when(discoveryChannel.newCall(Mockito.eq(DiscoveryServiceGrpc.getListEndpointsMethod()), Mockito.any()))
+                .thenReturn(MockedCall.unavailable());
+
+        CompletableFuture<Void> isReady = new CompletableFuture<>();
+
+        @SuppressWarnings("deprecation")
+        GrpcTransport transport = GrpcTransport.forConnectionString("grpc://mocked:2136/local")
+                .withSchedulerFactory(() -> scheduler)
+                .withDiscoveryTimeout(Duration.ofMillis(100))
+                .withChannelFactoryBuilder(builder -> channelFactory)
+                .buildAsync(() -> isReady.complete(null));
+
+        Assert.assertNotNull(transport);
+        Assert.assertFalse(isReady.isDone());
+
+        // Run discovery task and ready-watcher task
+        scheduler.hasTasksCount(2).runNextTask().runNextTask();
+
+        // readyWatcher must be called even if discovery fails
+        Assert.assertTrue(isReady.isDone());
+
+        transport.close();
+    }
+
     @Test
     @SuppressWarnings("SleepWhileInLoop")
     public void asyncWaitingForReadyTest() throws Exception {