From c7cfc074b6e483f332d37b574e19fcb9ae74649e Mon Sep 17 00:00:00 2001
From: Donal McBreen <donal@basecamp.com>
Date: Wed, 6 Mar 2024 15:40:21 +0000
Subject: [PATCH] Ensure a minimum limit of 1 for % boot strategy

Fixes: https://github.com/basecamp/kamal/issues/681
---
 lib/kamal/configuration/boot.rb                 |  2 +-
 test/commander_test.rb                          |  6 ++++++
 ...deploy_with_low_percentage_boot_strategy.yml | 17 +++++++++++++++++
 .../deploy_with_percentage_boot_strategy.yml    |  2 +-
 4 files changed, 25 insertions(+), 2 deletions(-)
 create mode 100644 test/fixtures/deploy_with_low_percentage_boot_strategy.yml

diff --git a/lib/kamal/configuration/boot.rb b/lib/kamal/configuration/boot.rb
index f6daa1fa..e5cf5a6e 100644
--- a/lib/kamal/configuration/boot.rb
+++ b/lib/kamal/configuration/boot.rb
@@ -8,7 +8,7 @@ class Kamal::Configuration::Boot
     limit = @options["limit"]
 
     if limit.to_s.end_with?("%")
-      @host_count * limit.to_i / 100
+      [@host_count * limit.to_i / 100, 1].max
     else
       limit
     end
diff --git a/test/commander_test.rb b/test/commander_test.rb
index 4e848a4b..598fc56b 100644
--- a/test/commander_test.rb
+++ b/test/commander_test.rb
@@ -109,6 +109,12 @@ class CommanderTest < ActiveSupport::TestCase
     assert_equal({ in: :groups, limit: 1, wait: 2 }, @kamal.boot_strategy)
   end
 
+  test "percentage-based group strategy limit is at least 1" do
+    configure_with(:deploy_with_low_percentage_boot_strategy)
+
+    assert_equal({ in: :groups, limit: 1, wait: 2 }, @kamal.boot_strategy)
+  end
+
   test "try to match the primary role from a list of specific roles" do
     configure_with(:deploy_primary_web_role_override)
 
diff --git a/test/fixtures/deploy_with_low_percentage_boot_strategy.yml b/test/fixtures/deploy_with_low_percentage_boot_strategy.yml
new file mode 100644
index 00000000..9b6a3c64
--- /dev/null
+++ b/test/fixtures/deploy_with_low_percentage_boot_strategy.yml
@@ -0,0 +1,17 @@
+service: app
+image: dhh/app
+servers:
+  web:
+    - "1.1.1.1"
+    - "1.1.1.2"
+  workers:
+    - "1.1.1.3"
+    - "1.1.1.4"
+
+registry:
+  username: user
+  password: pw
+
+boot:
+  limit: 1%
+  wait: 2
diff --git a/test/fixtures/deploy_with_percentage_boot_strategy.yml b/test/fixtures/deploy_with_percentage_boot_strategy.yml
index eb68a52f..9b6a3c64 100644
--- a/test/fixtures/deploy_with_percentage_boot_strategy.yml
+++ b/test/fixtures/deploy_with_percentage_boot_strategy.yml
@@ -13,5 +13,5 @@ registry:
   password: pw
 
 boot:
-  limit: 25%
+  limit: 1%
   wait: 2