File Coverage

lib/VM/EC2/Security/CredentialCache.pm

Criterion	Covered	Total	%
statement	10	12	83.3
branch			n/a
condition			n/a
subroutine	4	4	100.0
pod			n/a
total	14	16	87.5

package VM::EC2::Security::CredentialCache;
$VM::EC2::Security::CredentialCache::VERSION = '0.23';
use strict;
use warnings;
use DateTime::Format::ISO8601;
use VM::EC2::Instance::Metadata;

=head1 NAME

VM::EC2::Security::CredentialCache -- Cache credentials respecting expiration time for IAM roles.

=head1 SYNOPSIS

Retrieves the current EC2 instance's IAM credentials and caches them until they expire.

  use VM::EC2::Security::CredentialCache;

  # return a VM::EC2::Security::Credentials if avaiable undef otherwise.
  my $credentials = VM::EC2::Security::CredentialCache->get();

=head1 DESCRIPTION

This module provides a cache for an EC2's IAM credentials represented by L.
Rather than retriving the credentials for every possible call that uses them, cache them until they
expire and retreive them again if they have expired.

=cut

my $credentials;
my $credential_expiration_dt;

sub get {
    my ($self, $now) = @_;
    if (!defined($credentials)) {
        my $meta = VM::EC2::Instance::Metadata->new;
        defined($meta) || die("Unable to retrieve instance metadata");
        $credentials= $meta->iam_credentials;
        defined($credentials) || die("No IAM credentials retrieved from instance metadata");
        $credential_expiration_dt = DateTime::Format::ISO8601->parse_datetime($credentials->expiration())->epoch();
        return $credentials;
    }

    # AWS provides new credentials atleast 5 minutes before the expiration of the old
    # credentials, but we'll only start looking at 4 minutes
    $now //= time;
    if ($credential_expiration_dt - $now > 240) {
        return $credentials;
    }

    # These credentials are good for only 4 minutes or less, so clear them and attempt to
    # retrieve new credentials.
    $credentials = undef;
    $credential_expiration_dt = undef;
    return get();
}

1;