Treat LOADING Errors as Connection Failures to Retry with Next Replica (#1536)

mustafaakbel · Mustafa AKBEL · tillkruss · web-flow · commit 6021daf9cdb2 · 2025-05-28T15:11:13.000+03:00
* fix(sentinel-replication): Treat LOADING error responses as ConnectionException to allow retry mechanism to discard the current replica and switch to the next available one.

* fix(sentinel-replication): add changelog entries for LOADING response handling

* Update CHANGELOG.md

* Update CHANGELOG.md

---------

Co-authored-by: Mustafa AKBEL &lt;mustafa.akbel@pusula.net.tr&gt;
Co-authored-by: Till Krüss &lt;tillkruss@users.noreply.github.com&gt;
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -1,6 +1,9 @@
 ## Changelog
 
 ## Unreleased
+### Changed
+- Handle and retry `LOADING` errors from Sentinel replicas (#1536)
+
 ### Fixed
 - Fixed PHP 8.4 deprecated call to `stream_context_set_option()` (#1545)
 - Fixed return type for `ZCOUNT` to be `int` (#1547)
diff --git a/src/Connection/Replication/SentinelReplication.php b/src/Connection/Replication/SentinelReplication.php
@@ -715,6 +715,9 @@ private function retryCommandOnFailure(CommandInterface $command, $method)
         while ($retries <= $this->retryLimit) {
             try {
                 $response = $this->getConnectionByCommand($command)->$method($command);
+                if ($response instanceof Error && $response->getErrorType() === 'LOADING') {
+                    throw new ConnectionException($this->current, $response->getMessage());
+                }
                 break;
             } catch (CommunicationException $exception) {
                 $this->wipeServerList();
diff --git a/tests/Predis/Connection/Replication/SentinelReplicationTest.php b/tests/Predis/Connection/Replication/SentinelReplicationTest.php
@@ -1599,6 +1599,91 @@ public function connectionsProvider(): array
         ];
     }
 
+    /**
+     * @group disconnected
+     */
+    public function testDiscardsSlaveWhenRespondsLOADINGAndExecutesReadOnlyCommandOnNextSlave(): void
+    {
+        $sentinel1 = $this->getMockSentinelConnection('tcp://127.0.0.1:5381?role=sentinel');
+        $sentinel1
+            ->expects($this->any())
+            ->method('executeCommand')
+            ->with($this->isRedisCommand(
+                'SENTINEL', ['slaves', 'svc']
+            ))
+            ->willReturn(
+                [
+                    [
+                        'name', '127.0.0.1:6383',
+                        'ip', '127.0.0.1',
+                        'port', '6383',
+                        'runid', '1c0bf1291797fbc5608c07a17da394147dc62817',
+                        'flags', 'slave',
+                        'master-host', '127.0.0.1',
+                        'master-port', '6381',
+                    ],
+                ]
+            );
+
+        $master = $this->getMockConnection('tcp://127.0.0.1:6381?role=master');
+        $master
+            ->expects($this->any())
+            ->method('isConnected')
+            ->willReturn(true);
+
+        $slave1 = $this->getMockConnection('tcp://127.0.0.1:6382?role=slave');
+        $slave1
+            ->expects($this->any())
+            ->method('isConnected')
+            ->willReturn(true);
+        $slave1
+            ->expects($this->once())
+            ->method('executeCommand')
+            ->with(
+                $this->isRedisCommand('GET', ['key'])
+            )
+            ->willReturn(
+                new Response\Error('LOADING')
+            );
+
+        $slave2 = $this->getMockConnection('tcp://127.0.0.1:6383?role=slave');
+        $slave2
+            ->expects($this->any())
+            ->method('isConnected')
+            ->willReturn(true);
+        $slave2
+            ->expects($this->once())
+            ->method('executeCommand')
+            ->withConsecutive(
+                [$this->isRedisCommand('GET', ['key'])]
+            )
+            ->willReturnOnConsecutiveCalls(
+                'value'
+            );
+
+        /** @var Connection\FactoryInterface|MockObject */
+        $factory = $this->getMockBuilder('Predis\Connection\FactoryInterface')->getMock();
+        $factory
+            ->expects($this->once())
+            ->method('create')
+            ->with([
+                'host' => '127.0.0.1',
+                'port' => '6383',
+                'role' => 'slave',
+            ])
+            ->willReturn($slave2);
+
+        $replication = $this->getReplicationConnection('svc', [$sentinel1], $factory);
+
+        $replication->add($master);
+        $replication->add($slave1);
+
+        $this->assertSame('value', $replication->executeCommand(
+            Command\RawCommand::create('get', 'key')
+        ));
+        $this->assertSame($slave2, $replication->getCurrent());
+    }
+
     // ******************************************************************** //
     // ---- HELPER METHODS ------------------------------------------------ //
     // ******************************************************************** //
