Apache错误日志-服务器过载

也许一些专家可以帮助我解决这个问题：我在Apache日志上收到以下错误，这种情况主要发生在流量高的时候，每一两分钟一次，但在一天的其余时间里，这种情况也每5-10分钟一次。我有一个32核的服务器，内存为128gb，使用mpm事件Apache 2.4和keepalive on，最大客户端为3000。这只适用于Apache，我正在连接到一个远程MySQL专用服务器。

[Wed May 18 09:04:23.304162 2016] [core:error] [pid 14427:tid 109067598780160] [client 223.227.170.67:15501] AH00524: Handler for (null) returned invalid result code 70007, referer: https:$
[Wed May 18 09:08:48.716167 2016] [core:error] [pid 23012:tid 109067562034944] [client 103.246.201.7:20716] AH00524: Handler for (null) returned invalid result code 70007, referer: https:/$
[Wed May 18 09:11:33.056162 2016] [core:error] [pid 11230:tid 109067733079808] [client 103.246.201.58:16297] AH00524: Handler for (null) returned invalid result code 70007, referer: https:$
[Wed May 18 09:12:19.544211 2016] [core:error] [pid 16838:tid 109067831011072] [client 103.246.200.28:47581] AH00524: Handler for (null) returned invalid result code 70007, referer: https:$
[Wed May 18 09:13:27.176166 2016] [core:error] [pid 14427:tid 109067831084800] [client 103.246.201.25:32601] AH00524: Handler for (null) returned invalid result code 70007, referer: https:$
[Wed May 18 09:14:38.224143 2016] [core:error] [pid 11230:tid 109067697231616] [client 223.227.170.67:15410] AH00524: Handler for (null) returned invalid result code 70007, referer: https:$
[Wed May 18 09:15:21.600233 2016] [core:error] [pid 14427:tid 109067705698048] [client 103.246.200.31:60991] AH00524: Handler for (null) returned invalid result code 70007, referer: https:$
[Wed May 18 09:16:42.652179 2016] [core:error] [pid 9205:tid 109067659392768] [client 103.246.201.37:14295] AH00524: Handler for (null) returned invalid result code 70007, referer: https:/$
[Wed May 18 09:19:06.356158 2016] [core:error] [pid 9205:tid 109067740841728] [client 103.246.201.4:21377] AH00524: Handler for (null) returned invalid result code 70007, referer: https://$
[Wed May 18 09:19:10.388161 2016] [core:error] [pid 11230:tid 109067705874176] [client 103.246.200.5:29111] AH00524: Handler for (null) returned invalid result code 70007, referer: https:/$
[Wed May 18 09:27:51.292172 2016] [core:error] [pid 11230:tid 109067598817024] [client 103.246.200.37:31527] AH00524: Handler for (null) returned invalid result code 70007, referer: https:$
[Wed May 18 09:29:15.904172 2016] [core:error] [pid 23917:tid 109067616036608] [client 103.246.201.44:41459] AH00524: Handler for (null) returned invalid result code 70007, referer: https:$

"refer"不仅仅是一个文件，它似乎随机出现在我网站的任何页面上。我认为我没有太多的流量来认为服务器过载，但我找不到解决这个问题的方法。知道从哪里开始搜索这个问题吗？提前谢谢。