我们的服务器宕机了，我们重新启动了服务（nginx & httpd），当我查看日志时，我发现这些行，有这么多Graceful restart requested, doing restart行，怎么了？我有 100 行如下
[Tue Nov 10 03:35:12.421652 2015] [mpm_prefork:notice] [pid 60224] AH00163: Apache/2.4.6 (CentOS) PHP/5.6.7 mod_apreq2-20090110/2.8.0 mod_perl/2.0.9dev Perl/v5.16.3 configured -- resuming normal operations
[Tue Nov 10 03:35:12.421669 2015] [core:notice] [pid 60224] AH00094: Command line: '/usr/sbin/httpd -D FOREGROUND'
JPEG datastream contains no image
JPEG datastream contains no image
JPEG datastream contains no image
Empty input file
[Wed Nov 11 03:37:09.103375 2015] [mpm_prefork:notice] [pid 60224] AH00171: Graceful restart requested, doing restart
[Wed Nov 11 …