Forum Discussion

GEAH_138957's avatar
GEAH_138957
Icon for Nimbostratus rankNimbostratus
Dec 02, 2013

why http 503 is returned to the client

Hi,

 

I am a newbie to F5.

 

F5 BigIP 6900 BigIP 10.2.0 build 1707

 

I have a F5 in front of my nginx. My nginx sits in front of a tomcat.

 

My client (a mobile app) uploads a file (500kb let's say) via HTTP POST.

 

Both my nginx error.log and tomcat log indicated that a 200 was returned, but the client received a 503.

 

How can I find out where F5 returns a http status code 503 or not? It has to come from somewhere and I am almost positive that it's not from nginx or tomcat.

 

It happens sporadically, on some devices, but not all the time. We need some logging on F5 to determine what's going on.

 

Please point me to the right documentation.

 

APM
application delivery
deployment
devops
http status
iRules
management
security

3 Replies

Sort By
  • PeteWhite's avatar
    PeteWhite
    Icon for Employee rankEmployee
    Dec 02, 2013

    There are number of things that you can do. Start by running tcpdump on the f5 internal and external interfaces to see properly what is going on. tcpdump -i -s0 -w /var/tmp/_1.cap host and port

     

    in a different window, run tcpdump -i -s0 -w /var/tmp/_1.cap host or etc

     

    This should capture the traffic. If it is SSL then use ssldump to decrypt it - ssldump -Aer -k -r _1.cap>>/var/tmp/ssldump_1.txt

     

    Copy the files off with SCP, open them in Wireshark and look at both sides of the connection.

     

  • IheartF5_45022's avatar
    IheartF5_45022
    Icon for Nacreous rankNacreous
    Dec 03, 2013

    The F5 would never 'alter' a response (unless you are doing so in an iRule). Are you sure there's no corporate proxy in the way (between client and F5)? Proxies will give you 503 if they get a RST, or if the backend server fails to respond.