From 42c2d2f3872323f2435891ea88612740627b73c2 Mon Sep 17 00:00:00 2001
From: Graham Christensen <graham@grahamc.com>
Date: Thu, 26 Aug 2021 12:54:38 -0400
Subject: [PATCH] Hydra::Math: add an exponential_backoff function

---
 src/lib/Hydra/Math.pm | 30 ++++++++++++++++++++++++++++++
 t/Math.t              | 19 +++++++++++++++++++
 2 files changed, 49 insertions(+)
 create mode 100644 src/lib/Hydra/Math.pm
 create mode 100644 t/Math.t

diff --git a/src/lib/Hydra/Math.pm b/src/lib/Hydra/Math.pm
new file mode 100644
index 00000000..40c7f335
--- /dev/null
+++ b/src/lib/Hydra/Math.pm
@@ -0,0 +1,30 @@
+package Hydra::Math;
+
+use strict;
+use warnings;
+use List::Util qw(min);
+use Exporter 'import';
+our @EXPORT_OK = qw(exponential_backoff);
+
+=head2 exponential_backoff
+
+Calculates a number of seconds to wait before reattempting something.
+
+Arguments:
+
+=over 1
+
+=item C<$attempts>
+
+Integer number of attempts made.
+
+=back
+
+=cut
+sub exponential_backoff {
+    my ($attempt) = @_;
+    my $clamp = min(10, $attempt);
+    return 2 ** $clamp;
+}
+
+1;
diff --git a/t/Math.t b/t/Math.t
new file mode 100644
index 00000000..a9a49b6f
--- /dev/null
+++ b/t/Math.t
@@ -0,0 +1,19 @@
+use strict;
+use warnings;
+use Setup;
+
+use Hydra::Math qw(exponential_backoff);
+
+use Test2::V0;
+
+subtest "exponential_backoff" => sub {
+    is(exponential_backoff(0), 1);
+    is(exponential_backoff(1), 2);
+    is(exponential_backoff(2), 4);
+    is(exponential_backoff(9), 512);
+    is(exponential_backoff(10), 1024);
+    is(exponential_backoff(11), 1024, "we're clamped to 1024 seconds");
+    is(exponential_backoff(11000), 1024, "we're clamped to 1024 seconds");
+};
+
+done_testing;