一、代码如下：
$producer->sendBatch([
new ProduceMessage('test', 'hyperf1_value', 'hyperf1_key'),
new ProduceMessage('test', 'hyperf2_value', 'hyperf2_key'),
new ProduceMessage('test', 'hyperf3_value', 'hyperf3_key'),
]);

二、错误如下：
Notice: Undefined index: in /var/www/hyperf/vendor/hyperf/kafka/src/Producer.php on line 204
[ERROR] Return value of Hyperf\Kafka\Producer::getMessageBrokerId() must be of the type int, null returned[204] in /var/www/hyperf/vendor/hyperf/kafka/src/Producer.php
[ERROR] #0 /var/www/hyperf/vendor/hyperf/kafka/src/Producer.php(197): Hyperf\Kafka\Producer->getMessageBrokerId(Object(longlang\phpkafka\Producer\ProduceMessage))
#1:The requested offset is not within the range of offsets maintained by the server /var/www/hyperf/vendor/hyperf/kafka/src/Producer.php(101): Hyperf\Kafka\Producer->slitByBroker(Array)
#2:一次性投递多条消息的问题 [internal function]: Hyperf\Kafka\Producer->Hyperf\Kafka{closure}()
#3 /var/www/hyperf/vendor/hyperf/kafka/src/Producer.php(149): Closure->call(Object(Hyperf\Kafka\Producer))
#4 {main}

三、运行环境如下：
PHP 7.4.13 (cli) (built: Dec 1 2020 04:18:12) ( NTS )
Copyright (c) The PHP Group
Zend Engine v3.4.0, Copyright (c) Zend Technologies

swoole

Swoole => enabled
Author => Swoole Team team@swoole.com
Version => 4.5.9
Built => Dec 6 2020 23:04:53
coroutine => enabled
epoll => enabled
eventfd => enabled
signalfd => enabled
cpu_affinity => enabled
spinlock => enabled
rwlock => enabled
sockets => enabled
openssl => OpenSSL 1.1.1d 10 Sep 2019
http2 => enabled
pcre => enabled
zlib => 1.2.11
mutex_timedlock => enabled
pthread_barrier => enabled
futex => enabled
async_redis => enabled

Directive => Local Value => Master Value
swoole.enable_coroutine => On => On
swoole.enable_library => On => On
swoole.enable_preemptive_scheduler => Off => Off
swoole.display_errors => On => On
swoole.use_shortname => On => On
swoole.unixsock_buffer_size => 8388608 => 8388608
longlang/phpkafka v1.1.4 A kafka client. Support php-fpm and Swoole.