+ my ($streamname, $filename);
+ my $image = retry_op(sub {
+ $arv->{collections}->{get}->execute(uuid => $locator);
+ });
+ if ($image) {
+ foreach my $line (split(/\n/, $image->{manifest_text})) {
+ my @tokens = split(/\s+/, $line);
+ next if (!@tokens);
+ $streamname = shift(@tokens);
+ foreach my $filedata (grep(/^\d+:\d+:/, @tokens)) {
+ if (defined($filename)) {
+ return (undef, undef); # More than one file in the Collection.
+ } else {
+ $filename = (split(/:/, $filedata, 3))[2];
+ }
+ }
+ }
+ }
+ if (defined($filename) and ($filename =~ /^([0-9A-Fa-f]{64})\.tar$/)) {
+ return ($streamname, $1);
+ } else {
+ return (undef, undef);
+ }
+}
+
+sub retry_count {
+ # Calculate the number of times an operation should be retried,
+ # assuming exponential backoff, and that we're willing to retry as
+ # long as tasks have been running. Enforce a minimum of 3 retries.
+ my ($starttime, $endtime, $timediff, $retries);
+ if (@jobstep) {
+ $starttime = $jobstep[0]->{starttime};
+ $endtime = $jobstep[-1]->{finishtime};
+ }
+ if (!defined($starttime)) {
+ $timediff = 0;
+ } elsif (!defined($endtime)) {
+ $timediff = time - $starttime;
+ } else {
+ $timediff = ($endtime - $starttime) - (time - $endtime);
+ }
+ if ($timediff > 0) {
+ $retries = int(log($timediff) / log(2));
+ } else {
+ $retries = 1; # Use the minimum.
+ }
+ return ($retries > 3) ? $retries : 3;
+}
+
+sub retry_op {
+ # Given a function reference, call it with the remaining arguments. If
+ # it dies, retry it with exponential backoff until it succeeds, or until
+ # the current retry_count is exhausted.
+ my $operation = shift;
+ my $retries = retry_count();
+ foreach my $try_count (0..$retries) {
+ my $next_try = time + (2 ** $try_count);
+ my $result = eval { $operation->(@_); };
+ if (!$@) {
+ return $result;
+ } elsif ($try_count < $retries) {
+ my $sleep_time = $next_try - time;
+ sleep($sleep_time) if ($sleep_time > 0);