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Sawan_312205's avatar
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Jun 21, 2017

503 service unavailable error

Hi, I have a physical server which sits behind the loadbalancer. When development team generates a load of 100 users on the representing virtual it works fine but later they start getting 503 code error when they increase the load upto 200 users.


Few things which I have already checked- - Irule is there but it's just logging the connection IP info - Confirmed that the connection limit is set to 0 (means to unlimited)


Tomorrow I will be doing tcpdump to see the exact traffic/packets. Could you please suggest if there is anything extra which I can check?


2 Replies

  • The 503 is a server side error. I do not believe this is the BIGIP. this 503 is when the website is not available and the server sends a 503. Since this happens when the load is increase I will check the number of threads in the server. I think you are getting max out on the threads available in the server side.


  • Hi,


    Not much except checking via tcpdump on internal VLAN if 503 is coming from your backend server, if so then you have performance issue at backend server side.


    One more thing, if you are using HTTP monitor send string without Connection: close header then it's possible that monitor traffic can create a lot of open TCP connections on the backend server - could be part of the issue.