hydra-send-stats: add a --once option for testing

src/script/hydra-send-stats

@@ -6,6 +6,7 @@ use Hydra::Helper::Nix;
 use Net::Statsd;
 use File::Slurp;
 use JSON;
+use Getopt::Long qw(:config gnu_getopt);
 
 STDERR->autoflush(1);
 binmode STDERR, ":encoding(utf8)";
@@ -65,6 +66,26 @@ sub sendQueueRunnerStats {
     gauge("hydra.queue.machines.in_use", scalar(grep { $_->{currentJobs} > 0 } (values %{$json->{machines}})));
 }
 
+
+sub showHelp {
+    print <<EOF;
+Usage: $0 [--once]
+
+Send stats to statsd. The --once flag can be used to send one round
+of stats and then exit.
+
+Example:
+  \$ $0 --once
+EOF
+    exit 0;
+}
+
+my $once = 0;
+
+GetOptions("once" => \$once,
+           "help" => sub { showHelp() }
+    ) or exit 1;
+
 while (1) {
     eval {
         sendQueueRunnerStats();
@@ -78,5 +99,8 @@ while (1) {
         gauge("hydra.mem.dirty", $dirty);
     }
 
+    if ($once) {
+        last;
+    }
     sleep(30);
 }