Redirect stdout loggers to stderr preventing json response polutions

Author: josbeir

src/Command/SubprocessJobRunnerCommand.php

@@ -20,6 +20,7 @@
 use Cake\Console\Arguments;
 use Cake\Console\ConsoleIo;
 use Cake\Core\ContainerInterface;
+use Cake\Log\Log;
 use Cake\Queue\Job\Message;
 use Cake\Queue\Queue\Processor;
 use Enqueue\Null\NullConnectionFactory;
@@ -84,6 +85,11 @@ public function execute(Arguments $args, ConsoleIo $io): int
             return self::CODE_ERROR;
         }
 
+        // Redirect the configured logger to STDERR to keep STDOUT clean for JSON output
+        if (isset($data['logger'])) {
+            $this->redirectLoggerToStderr($data['logger']);
+        }
+
         try {
             $result = $this->executeJob($data);
             $this->outputResult($io, [
@@ -184,4 +190,43 @@ protected function outputResult(ConsoleIo $io, array $result): void
             $io->out($json);
         }
     }
+
+    /**
+     * Redirect a specific logger to STDERR to keep STDOUT clean for JSON.
+     *
+     * Only redirects the 'stdout' logger to prevent it from corrupting JSON output.
+     * Other loggers are left unchanged as they don't interfere with STDOUT.
+     *
+     * @param string $loggerName Logger name to redirect
+     * @return void
+     */
+    protected function redirectLoggerToStderr(string $loggerName): void
+    {
+        // Only redirect the 'stdout' logger, leave all others untouched
+        if ($loggerName !== 'stdout') {
+            return;
+        }
+
+        $config = Log::getConfig($loggerName);
+        if ($config === null) {
+            // Logger not configured, nothing to redirect
+            return;
+        }
+
+        $className = $config['className'] ?? null;
+        if (!is_string($className)) {
+            // Logger is an object instance, we can't reconfigure it
+            return;
+        }
+
+        // Only redirect console loggers that write to STDOUT
+        if (str_contains($className, 'Console')) {
+            $stream = $config['stream'] ?? 'php://stdout';
+            if ($stream === 'php://stdout') {
+                $config['stream'] = 'php://stderr';
+                Log::drop($loggerName);
+                Log::setConfig($loggerName, $config);
+            }
+        }
+    }
 }

src/Queue/SubprocessProcessor.php

@@ -185,6 +185,7 @@ protected function prepareJobData(QueueMessage $message): array
             'messageClass' => get_class($message),
             'body' => $body,
             'properties' => $properties,
+            'logger' => $this->config['logger'] ?? null,
         ];
     }
 

tests/TestCase/Command/SubprocessJobRunnerCommandTest.php

@@ -24,6 +24,7 @@
 use Enqueue\Null\NullMessage;
 use Interop\Queue\Processor;
 use ReflectionClass;
+use TestApp\Job\LogToDebugJob;
 use TestApp\TestProcessor;
 
 class SubprocessJobRunnerCommandTest extends TestCase
@@ -252,4 +253,61 @@ public function testOutputResult(): void
 
         $method->invoke($command, $io, ['success' => true, 'result' => 'ack']);
     }
+
+    /**
+     * Test that logs are redirected to STDERR and don't corrupt JSON output
+     */
+    public function testLogsRedirectedToStderr(): void
+    {
+        $jobData = [
+            'messageClass' => NullMessage::class,
+            'body' => [
+                'class' => [LogToDebugJob::class, 'execute'],
+                'args' => [['foo' => 'bar']],
+            ],
+            'properties' => [],
+        ];
+
+        $command = 'php ' . ROOT . 'bin/cake.php queue subprocess-runner';
+
+        $descriptors = [
+            0 => ['pipe', 'r'],
+            1 => ['pipe', 'w'],
+            2 => ['pipe', 'w'],
+        ];
+
+        $process = proc_open($command, $descriptors, $pipes);
+        $this->assertIsResource($process);
+
+        // Write job data to STDIN
+        $jobDataJson = json_encode($jobData);
+        if ($jobDataJson !== false) {
+            fwrite($pipes[0], $jobDataJson);
+        }
+
+        fclose($pipes[0]);
+
+        // Read STDOUT (should be clean JSON only)
+        $stdout = stream_get_contents($pipes[1]);
+        fclose($pipes[1]);
+
+        // Read STDERR to prevent pipe blocking
+        stream_get_contents($pipes[2]);
+        fclose($pipes[2]);
+
+        proc_close($process);
+
+        // STDOUT should be valid JSON without any log messages
+        $result = json_decode($stdout, true);
+        $this->assertIsArray($result, 'STDOUT should contain valid JSON: ' . $stdout);
+        $this->assertArrayHasKey('success', $result);
+        $this->assertTrue($result['success']);
+        $this->assertSame(Processor::ACK, $result['result']);
+
+        // STDOUT should not contain log text
+        $this->assertStringNotContainsString('Debug job was run', $stdout);
+
+        // STDERR may contain log messages (depends on log configuration)
+        // We just verify it doesn't interfere with JSON parsing
+    }
 }