Properly handle Asana API rate limit in perl - perl

Question

Please accept my apology if this is something terribly obvious that I am simply missing. I have a perl script that hits the Asana restful API at a burst rate of a bit more than 100 calls per minute. When I stress test it, I do occasionally hit their rate limit and see error 429. I know from reading Asana's documentation that it will return a "retry-after" response header but I can't figure out for the life of me how to retrieve / open / read this header. Any advice you can provide would be appreciated.
Edit:
My code is attached below. Of course I've erased sensitive information such as my API key and project number, but the core code is here. If I run this just once, it doesn't produce enough calls per minute to trigger an error. I have to run it about 3-4 times simultaneously to produce the error. One might say "well don't do that." While correct, the point of this exercise is to produce the error, so running it four times simultaneously is good.
When you do so with a valid API key and project number, occasionally you will get this error:
{"errors":[{"message":"You have made too many requests recently. Please, be chill."}]}
My question is how to retrieve the header that apparently includes a retry-after field along with a number of seconds. I may just resort to building in a delay of 20 seconds every time an error is returned, but I'd prefer to handle the error more elegantly.
#!/usr/local/bin/perl
my $counter = 0;
my $AsanaAPIcode = "...";
my $AsanaProjectID = "...";
my $AsanaFullString = 'curl -u ' . $AsanaAPIcode . ': https://app.asana.com/api/1.0/projects/' . $AsanaProjectID . '?opt_fields=archived';
my $APIoutput = `$AsanaFullString`;
print $APIoutput;
my $startTime = time;
my $totalCount = 200;
while ($counter<=$totalCount) {
print $counter . "\n";
$APIoutput = `$AsanaFullString`;
print $APIoutput . "\n";
$counter++;
}
my $endTime = time;
my $totalTime = $endTime - $startTime;
print "Total time = " . $totalTime . " seconds.\n";
print $totalCount / ($totalTime / 60) . " API calls per minute.\n";
print "end";

Answer 1

The 'Retry-After' is in the HTTP response, which is lost by the backtick call to curl.
A clunky solution is to use 'curl -D' (--dump-headers) which will drop all HTTP headers into the response, which you'd then have to parse and remove.
A better solution would be to use the LWP library (perldoc LWP::UserAgent).
Obviously I can't test this code without an API key...
I think you can inject these into the URL (https://name:password#app.asana.com/api...)
use LWP::UserAgent;
use LWP::Protocol::https;
my $agent = LWP::UserAgent->new(); # check LWP docs for extra params
my $request = LWP::Request->new( 'https://app.asana.com/api/1.0/projects/' . $AsanaProjectID . '?opt_fields=archived' )
my $response = $ua->request($request);
if ($response->code == 429) {
my $retry = $response->header('Retry-After');
...
}
Or...you could try CPAN for something like WWW::Asana.
http://search.cpan.org/dist/WWW-Asana/

Answer 2

We ran into the issue with our Asana Connector for Klok. We contacted the folks at Asana and they were willing to add the "retry after" amount into the body of the response. So, you can now grab it from the "retry_after" property:
{
"errors":[{"message":"You have made too many requests recently. Please, be chill."}],
"retry_after":30
}
This was a big help for us since we are using Adobe AIR 2.x which doesn't give us access to the response headers of an error response.

Answer 3

There is a CPAN module for that, WWW::Asana, and it handles the rate limit response properly.