分布式workerman，worker进程僵死

在分布式 Gateway和Worker分离的情况下，Worker忽然间爆发了大量错误：

GatewayConnection Error : 1 ,connect 172.16.17.4:4000 fail after 7.2382 seconds
GatewayConnection Error : 1 ,connect 172.16.17.4:4004 fail after 7.2382 seconds
GatewayConnection Error : 1 ,connect 172.16.17.4:4003 fail after 7.2381 seconds
GatewayConnection Error : 1 ,connect 172.16.17.4:4007 fail after 7.2379 seconds
GatewayConnection Error : 1 ,connect 172.16.17.4:4010 fail after 7.2379 seconds
GatewayConnection Error : 1 ,connect 172.16.17.4:4006 fail after 7.2379 seconds
GatewayConnection Error : 1 ,connect 172.16.17.4:4017 fail after 7.2379 seconds
GatewayConnection Error : 1 ,connect 172.16.17.4:4013 fail after 7.2379 seconds
GatewayConnection Error : 1 ,connect 172.16.17.4:4020 fail after 7.2379 seconds
GatewayConnection Error : 1 ,connect 172.16.17.4:4016 fail after 7.2378 seconds
GatewayConnection Error : 1 ,connect 172.16.17.4:4025 fail after 7.2376 seconds
GatewayConnection Error : 1 ,connect 172.16.17.4:4023 fail after 7.2376 seconds
GatewayConnection Error : 1 ,connect 172.16.17.4:4026 fail after 7.2376 seconds
GatewayConnection Error : 1 ,connect 172.16.17.4:4021 fail after 7.2374 seconds
GatewayConnection Error : 1 ,connect 172.16.17.4:4018 fail after 7.2374 seconds
GatewayConnection Error : 1 ,connect 172.16.17.4:4028 fail after 7.2374 seconds
GatewayConnection Error : 1 ,connect 172.16.17.4:4019 fail after 7.2374 seconds
GatewayConnection Error : 1 ,connect 172.16.17.4:4024 fail after 7.2374 seconds
GatewayConnection Error : 1 ,connect 172.16.17.4:4031 fail after 7.2374 seconds
GatewayConnection Error : 1 ,connect 172.16.17.5:4003 fail after 7.2374 seconds
GatewayConnection Error : 1 ,connect 172.16.17.5:4001 fail after 7.2374 seconds
GatewayConnection Error : 1 ,connect 172.16.17.5:4000 fail after 7.2374 seconds
GatewayConnection Error : 1 ,connect 172.16.17.5:4006 fail after 7.2374 seconds
GatewayConnection Error : 1 ,connect 172.16.17.5:4004 fail after 7.2373 seconds
GatewayConnection Error : 1 ,connect 172.16.17.5:4011 fail after 7.2373 seconds
GatewayConnection Error : 1 ,connect 172.16.17.5:4010 fail after 7.2373 seconds
GatewayConnection Error : 1 ,connect 172.16.17.5:4012 fail after 7.2373 seconds
GatewayConnection Error : 1 ,connect 172.16.17.5:4009 fail after 7.2373 seconds
GatewayConnection Error : 1 ,connect 172.16.17.5:4016 fail after 7.2373 seconds
GatewayConnection Error : 1 ,connect 172.16.17.5:4008 fail after 7.2373 seconds
GatewayConnection Error : 1 ,connect 172.16.17.5:4007 fail after 7.2374 seconds
GatewayConnection Error : 1 ,connect 172.16.17.5:4015 fail after 7.2374 seconds
GatewayConnection Error : 1 ,connect 172.16.17.5:4005 fail after 7.2374 seconds
GatewayConnection Error : 1 ,connect 172.16.17.5:4014 fail after 7.2374 seconds
GatewayConnection Error : 1 ,connect 172.16.17.5:4019 fail after 7.2374 seconds
GatewayConnection Error : 1 ,connect 172.16.17.5:4022 fail after 7.2374 seconds
GatewayConnection Error : 1 ,connect 172.16.17.5:4017 fail after 7.2374 seconds
GatewayConnection Error : 1 ,connect 172.16.17.5:4021 fail after 7.2374 seconds
GatewayConnection Error : 1 ,connect 172.16.17.5:4020 fail after 7.2374 seconds
GatewayConnection Error : 1 ,connect 172.16.17.5:4013 fail after 7.2374 seconds
GatewayConnection Error : 1 ,connect 172.16.17.5:4018 fail after 7.2374 seconds
GatewayConnection Error : 1 ,connect 172.16.17.5:4029 fail after 7.2374 seconds
GatewayConnection Error : 1 ,connect 172.16.17.5:4028 fail after 7.2374 seconds
GatewayConnection Error : 1 ,connect 172.16.17.5:4026 fail after 7.2374 seconds
GatewayConnection Error : 1 ,connect 172.16.17.5:4027 fail after 7.2373 seconds
GatewayConnection Error : 1 ,connect 172.16.17.5:4023 fail after 7.2374 seconds
GatewayConnection Error : 1 ,connect 172.16.17.5:4025 fail after 7.2374 seconds
GatewayConnection Error : 1 ,connect 172.16.17.5:4024 fail after 7.2374 seconds
GatewayConnection Error : 1 ,connect 172.16.17.5:4031 fail after 7.2374 seconds
GatewayConnection Error : 1 ,connect 172.16.17.5:4030 fail after 7.2374 seconds

php start.php stop停止worker后，进程中仍然有大量Worker僵尸进程没有被结束，仍然在不停的访问Gateway并提示本错误。
kill掉所有Worker僵尸进程后，重启回复正常。

请问发生这种情况会有哪些可能性？