fix: Fix task type starvation: collect all eligible task types then pick the oldest task

Co-authored-by: marcelklehr <986878+marcelklehr@users.noreply.github.com>

Author: Copilot

core/Command/TaskProcessing/WorkerCommand.php

@@ -105,16 +105,20 @@ protected function execute(InputInterface $input, OutputInterface $output): int
 	/**
 	 * Attempt to process one task across all preferred synchronous providers.
 	 *
+	 * To avoid starvation, all eligible task types are first collected and then
+	 * the oldest scheduled task across all of them is fetched in a single query.
+	 * This ensures that tasks are processed in the order they were scheduled,
+	 * regardless of which provider handles them.
+	 *
 	 * @param list<string> $taskTypes When non-empty, only providers for these task type IDs are considered.
 	 * @return bool True if a task was processed, false if no task was found
 	 */
 	private function processNextTask(OutputInterface $output, array $taskTypes = []): bool {
 		$providers = $this->taskProcessingManager->getProviders();
-		// Shuffle providers to avoid starvation: if providers are always iterated
-		// in the same order, a provider with a constant stream of tasks would
-		// prevent all subsequent providers from ever being processed.
-		shuffle($providers);
 
+		// Build a map of eligible taskTypeId => provider for all preferred synchronous providers
+		/** @var array<string, ISynchronousProvider> $eligibleProviders */
+		$eligibleProviders = [];
 		foreach ($providers as $provider) {
 			if (!$provider instanceof ISynchronousProvider) {
 				continue;
@@ -139,30 +143,40 @@ private function processNextTask(OutputInterface $output, array $taskTypes = [])
 				continue;
 			}
 
-			try {
-				$task = $this->taskProcessingManager->getNextScheduledTask([$taskTypeId]);
-			} catch (NotFoundException) {
-				continue;
-			} catch (Exception $e) {
-				$this->logger->error('Unknown error while retrieving scheduled TaskProcessing tasks', ['exception' => $e]);
-				continue;
-			}
+			$eligibleProviders[$taskTypeId] = $provider;
+		}
 
-			$output->writeln(
-				'Processing task ' . $task->getId() . ' of type ' . $taskTypeId . ' with provider ' . $provider->getId(),
-				OutputInterface::VERBOSITY_VERBOSE
-			);
+		if (empty($eligibleProviders)) {
+			return false;
+		}
 
-			$this->taskProcessingManager->processTask($task, $provider);
+		// Fetch the oldest scheduled task across all eligible task types in one query.
+		// This naturally prevents starvation: regardless of how many tasks one provider
+		// has queued, another provider's older tasks will be picked up first.
+		try {
+			$task = $this->taskProcessingManager->getNextScheduledTask(array_keys($eligibleProviders));
+		} catch (NotFoundException) {
+			return false;
+		} catch (Exception $e) {
+			$this->logger->error('Unknown error while retrieving scheduled TaskProcessing tasks', ['exception' => $e]);
+			return false;
+		}
 
-			$output->writeln(
-				'Finished processing task ' . $task->getId(),
-				OutputInterface::VERBOSITY_VERBOSE
-			);
+		$taskTypeId = $task->getTaskTypeId();
+		$provider = $eligibleProviders[$taskTypeId];
 
-			return true;
-		}
+		$output->writeln(
+			'Processing task ' . $task->getId() . ' of type ' . $taskTypeId . ' with provider ' . $provider->getId(),
+			OutputInterface::VERBOSITY_VERBOSE
+		);
+
+		$this->taskProcessingManager->processTask($task, $provider);
+
+		$output->writeln(
+			'Finished processing task ' . $task->getId(),
+			OutputInterface::VERBOSITY_VERBOSE
+		);
 
-		return false;
+		return true;
 	}
 }