Testing CDN Consistency with bash date time curl while loop

This is a simple one. Soa customer was complaining that after 3 minutes the cache time of the file on his CDN was changing. I wanted to built a way to test the consistency of the requests. Here is how I did it.

file curl-format.txt

     timenamelookup:  %{time_namelookup}\n
       time_connect:  %{time_connect}\n
    time_appconnect:  %{time_appconnect}\n
   time_pretransfer:  %{time_pretransfer}\n
      time_redirect:  %{time_redirect}\n
 time_starttransfer:  %{time_starttransfer}\n
                    ----------\n
         time_total:  %{time_total}\n

Short, simple, and to the point;

while ((1!=0)); do date; curl -w "@curl-format.txt" -o /dev/null -s "https://www.somecdndomain.secure.raxcdn.com/img/upload/3someimage_t32337827238.jpg"; done;

Output looks like:

                    ----------
         time_total:  0.395
Tue Feb  9 09:03:28 UTC 2016
      time_namelookup:  0.151
       time_connect:  0.154
    time_appconnect:  0.332
   time_pretransfer:  0.333
      time_redirect:  0.000
 time_starttransfer:  0.338
                    ----------
         time_total:  0.351
Tue Feb  9 09:03:28 UTC 2016
      time_namelookup:  0.151
       time_connect:  0.154
    time_appconnect:  0.324
   time_pretransfer:  0.324
      time_redirect:  0.000
 time_starttransfer:  0.331
                    ----------
         time_total:  0.347
Tue Feb  9 09:03:29 UTC 2016
      time_namelookup:  0.151
       time_connect:  0.154
    time_appconnect:  0.385
   time_pretransfer:  0.385
      time_redirect:  0.000
 time_starttransfer:  0.391
                    ----------
         time_total:  0.404
Tue Feb  9 09:03:29 UTC 2016
      time_namelookup:  0.151
       time_connect:  0.155
    time_appconnect:  0.348
   time_pretransfer:  0.349
      time_redirect:  0.000
 time_starttransfer:  0.357
                    ----------
         time_total:  0.374
Tue Feb  9 09:03:30 UTC 2016
      time_namelookup:  0.151
       time_connect:  0.155
    time_appconnect:  0.408
   time_pretransfer:  0.409
      time_redirect:  0.000
 time_starttransfer:  0.417
                    ----------
         time_total:  0.433
Tue Feb  9 09:03:30 UTC 2016

pretty handy andy.

With headers

# while ((1!=0)); do date; curl -IL -w "@curl-format.txt" -s "https://www.scdn3.secure.raxcdn.com/img/upload/3_sdsdsds6a9e80df0baa19863ffb8.jpg"; sleep 180; done;

2 thoughts on “Testing CDN Consistency with bash date time curl while loop

  1. Hey Blake,

    Thanks for writing chap. If this were a compiled code I might be able to find a good excuse, simply for the reason that a compiler should compile it the same as ‘an infinite loop’ and the assembly built at compile time would be optimized to that effect.

    Since BASH isn’t compiled, but is an interpreter for an interpreted language I believe it will evaluate the condition/expression each time, which is actually (very) bad. I think I was being a bit creative and got carried away, or was simply too lazy to do it properly. Nowadays programmers/scripters have too many cycles & memory, and as a result it gets used badly (in this case by me) 😀

    Thank you for some good feedback! I appreciate it!

    Best wishes,
    Adam

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