Troubleshooting webservice at OS level

We are trying to troubleshoot a webservice call that’s taking a lot of time. The initial idea it that the processing time in our platform is the issue. Let’s use curl at OS level with the configuration as explained here to troubleshoot.

This is the answer we get from the curl command:

{
"time_redirect": 0.000,
"time_namelookup": 5.515,
"time_connect": 5.630,
"time_appconnect": 6.008,
"time_pretransfer": 6.008,
"time_starttransfer": 6.385,
"time_total": 6.385,
"size_request": 375,
"size_upload": 103,
"size_download": 375,
"size_header": 343
}

Here we see 5+ seconds in the name resolution. A first workaround is to get the IP address of the target and bypass the name server by using the hostname file:

nslookup webexapis.com

we will get several answers:

Server:     100.125.4.25
Address:    100.125.4.25#53

Non-authoritative answer:
Name:   webexapis.com
Address: 3.130.32.130
Name:   webexapis.com
Address: 3.139.30.165
Name:   webexapis.com
Address: 3.140.133.193

we edit the /etc/hosts file and add that IP and host:

3.140.133.193 webexapis.com

if now we issue again the command, then let’s see if the issue is solved:

{
"time_redirect": 0.000,
"time_namelookup": 0.005,
"time_connect": 0.118,
"time_appconnect": 0.507,
"time_pretransfer": 0.507,
"time_starttransfer": 0.877,
"time_total": 0.877,
"size_request": 375,
"size_upload": 103,
"size_download": 375,
"size_header": 343
}

It seems the issue is related to the name server. Next step would be to troubleshoot the name server and see why it’s taking 5 seconds to resolve that url.