no, no, no!
Normally, it's not 0, but sometimes, the possibility is 0.07%. It's absolutely not normal!
[21/May/2013:00:02:56 +0800] "POST /ourservice/api HTTP/1.1" 200 607 27 "-" "c" "10.23.130.154"
[21/May/2013:00:02:56 +0800] "POST /ourservice/api HTTP/1.1" 200 613 27 "-" "c" "10.59.24.83"
[21/May/2013:00:02:56 +0800] "POST /ourservice/api HTTP/1.1" 200 604 62 "-" "e" "10.197.218.20"
[21/May/2013:00:02:57 +0800] "POST /ourservice/api HTTP/1.1" 200 491 27 "-" "f" "-"
[21/May/2013:00:02:57 +0800] "POST /ourservice/api HTTP/1.1" 200 612 278 "-" "f" "10.165.21.34"
[21/May/2013:00:02:57 +0800] "POST /ourservice/api HTTP/1.0" 200 816 27 "-" "c" "10.26.152.101"
[21/May/2013:00:02:57 +0800] "POST /ourservice/api HTTP/1.1" 200 585 27 "-" "c" "10.67.55.190"
[21/May/2013:00:02:57 +0800] "POST /ourservice/api HTTP/1.1" 200 463 211 "-" "f" "-"
[21/May/2013:00:02:57 +0800] "POST /ourservice/api HTTP/1.1" 200 596 0 "-" "f" "10.181.30.95"
You see the last column, the response content-length is 0. And we can't find the record in tomcat log. It seems nginx don't forward the request to tomcat.