今天伺服器突然出現接收不到資料 ，拿curl寫了個測試指令碼，發現只有小字串可以，收發成功，字串在300K就不行了，伺服器直接報‘500 Internal Server Error。
伺服器是centos6，nginx，php的環境
開始除錯，打開了php的錯誤日誌，並沒有發現任何錯誤資訊，檢查了下php的post的相關配置，配得都挺高也沒有任何問題。
繼續往下找原因，檢視nginx的錯誤日誌，然並卵，也沒有看到任何錯誤資訊，降低nginx的錯誤資訊級別為warn，這裡了，出現如下錯誤資訊：

2016/04/19 15:57:53 [crit] 23931#0: *143499 open() "/var/lib/nginx/tmp/client_body/0000000114"
 
 failed (13: Permission denied), client: 11.11.11.60, server: server4.dongdong.com, request: "POST /test1.php HTTP/1.1", host: "server4.dongdong.com"
2016/04/19 15:57:54 [crit] 23931#0: *143512 open() "/var/lib/nginx/tmp/client_body/0000000115" failed (13: Permission denied), client: 11.11.11.60, server: server4.dongdong.com, request
 
: "POST /test1.php HTTP/1.1", host: "server4.dongdong.com"
2016/04/19 15:57:54 [crit] 23931#0: *143515 open() "/var/lib/nginx/tmp/client_body/0000000116" failed (13: Permission denied), client: 11.11.11.60, server: server4.dongdong.com, request: "POST /test1.php HTTP/1.1", host: "server4.dongdong.com"
2016/04/19 15:57:54 [crit] 23931
 
#0: *143518 open() "/var/lib/nginx/tmp/client_body/0000000117" failed (13: Permission denied), client: 11.11.11.60, server: server4.dongdong.com, request: "POST /test1.php HTTP/1.1", host: "server4.dongdong.com"
2016/04/19 15:57:54 [crit] 23931#0: *143521 open() "/var/lib/nginx/tmp/client_body/0000000118" failed (13: Permission denied), client: 11.11.11.60, server: server4.dongdong.com, request: "POST /test1.php HTTP/1.1", host: "server4.dongdong.com"
2016/04/19 15:57:55 [crit] 23931#0: *143524 open() "/var/lib/nginx/tmp/client_body/0000000119" failed (13: Permission denied), client: 11.11.11.60, server: server4.dongdong.com, request: "POST /test1.php HTTP/1.1", host: "server4.dongdong.com"
2016/04/19 15:58:02 [crit] 23932#0: *143644 open() "/var/lib/nginx/tmp/client_body/0000000120" failed (13: Permission denied), client: 11.11.11.60, server: server4.dongdong.com, request: "POST /test1.php HTTP/1.1", host: "server4.dongdong.com"

根據錯誤資訊得出，nginx的buffer等檔案目錄沒有寫許可權。

chmod -R 775 /var/lib/nginx

問題解決！！！！