API rate limit using Cache::Mmap need help

swiftlet has asked for the wisdom of the Perl Monks concerning the following question:

I am going to implement an API rate limit function, allow several number of calls per second. Cache::FastMmap was my first choice, however, it's not working under threads. I am looking at Cache::Mmap, but I can't get it working even using the example from the module, it failed at write

use Cache::Mmap;

my %options = (
        expiry  => 3,
);
my $filename = "/tmp/cache-test";
$cache=Cache::Mmap->new($filename,\%options);

my $key1 = "Test";
$val1=$cache->read($key1);
print "read key1: $val1\n";
$val1++;
print "val1: $val1\n";
$cache->write($key1,$val1);
$val1=$cache->read($key1);
print "read key1 after write: $val1\n";
[download]

Error message:

main::(Cache-Mmap.pl:13):       print "val1: $val1\n";
  DB<1>
val1: 1
main::(Cache-Mmap.pl:14):       $cache->write($key1,$val1);
  DB<1>
not a reference at /usr/local/lib64/perl5/Cache/Mmap.pm line 1050.
 at /usr/lib64/perl5/vendor_perl/Storable.pm line 38.
        Storable::__ANON__[/usr/lib64/perl5/vendor_perl/Storable.pm:39
+]('not a reference') called at /usr/lib64/perl5/vendor_perl/Storable.
+pm line 335
        Storable::_freeze('CODE(0x185e640)', 1) called at /usr/lib64/p
+erl5/vendor_perl/Storable.pm line 319
        Storable::freeze(1) called at /usr/local/lib64/perl5/Cache/Mma
+p.pm line 1050
        Cache::Mmap::_encode('Cache::Mmap=HASH(0x197e3d0)', 1, 0) call
+ed at /usr/local/lib64/perl5/Cache/Mmap.pm line 401
        Cache::Mmap::write('Cache::Mmap=HASH(0x197e3d0)', 'Test', 1) c
+alled at Cache-Mmap.pl line 14
Debugged program terminated.  Use q to quit or R to restart,
  use o inhibit_exit to avoid stopping after program termination,
  h q, h R or h o to get additional info.
[download]

Any idea? Any other thread-safe modules for API rate limit implementation?

Comment on API rate limit using Cache::Mmap need help Select or Download Code

Replies are listed 'Best First'.
Re: API rate limit using Cache::Mmap need help by jcb (Parson) on Jul 27, 2020 at 03:00 UTC
While I am unfamiliar with Cache::Mmap, your error suggests that it is using Storable internally. You are trying to store a simple value, but `Storable` only works with references. Try changing your code like so: (untested) `my $key1 = "Test"; my $val1 = $cache->read($key1); print "read key1 count: ",$val1->{count},"\n"; $val1->{count}++; print "val1 count:",$val1->{count},"\n"; $cache->write($key1,$val1); $val1 = $cache->read($key1); print "read key1 count after write: ",$val1->{count},"\n";` [download] Note the change: the values stored in the cache are now hashrefs. You could also use scalar references, reading them with `$$val1` and incrementing with `${$val1}++`. Lastly, your code as written will not compile under strict. While it would not have caught this issue, good practice is to always `use strict;` and `use warnings;`.	[reply] [d/l] [select]
Re: API rate limit using Cache::Mmap need help by swiftlet (Acolyte) on Jul 29, 2020 at 08:34 UTC
Thanks all for your input, and thanks perlfan for the suggestions about Memcached and Redis. I am using Memcached now, which is working perfectly fine in my threaded codes.	[reply]
Re: API rate limit using Cache::Mmap need help by Anonymous Monk on Jul 27, 2020 at 10:55 UTC
Your code doesnt use threads	[reply]
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