Allow percentage-based rolling deployments

README.md

@@ -841,7 +841,7 @@ MRSK's default is to boot new containers on all hosts in parallel. But you can c
 service: myservice
 
 boot:
-  group_limit: 10
+  group_limit: 10 # Can also specify as a percentage of total hosts, such as "25%"
   group_wait: 2
 ```
 

lib/mrsk/configuration.rb

@@ -88,7 +88,7 @@ class Mrsk::Configuration
   end
 
   def boot
-    Mrsk::Configuration::Boot.new(section: raw_config.boot)
+    Mrsk::Configuration::Boot.new(config: self)
   end
 
 

lib/mrsk/configuration/boot.rb

@@ -1,9 +1,19 @@
 class Mrsk::Configuration::Boot
-  attr_reader :group_wait, :group_limit
+  def initialize(config:)
+    @options = config.raw_config.boot || {}
+    @host_count = config.all_hosts.count
+  end
 
-  def initialize(section:)
-    section = section || {}
-    @group_limit = section["group_limit"]
-    @group_wait = section["group_wait"]
+  def group_limit
+    limit = @options["group_limit"]
+    if limit.to_s.end_with?("%")
+      @host_count * limit.to_i / 100
+    else
+      limit
+    end
+  end
+
+  def group_wait
+    @options["group_wait"]
   end
 end

test/cli/app_test.rb

@@ -38,7 +38,7 @@ class CliAppTest < CliTestCase
     Mrsk::Cli::App.any_instance.stubs(:on).with([ "1.1.1.1" ]) # tag container
 
     # Strategy is used when booting the containers
-    Mrsk::Cli::App.any_instance.expects(:on).with([ "1.1.1.1" ], in: :groups, limit: 3, wait: 30).with_block_given
+    Mrsk::Cli::App.any_instance.expects(:on).with([ "1.1.1.1" ], in: :groups, limit: 3, wait: 2).with_block_given
 
     run_command("boot", config: :with_group_strategy)
   end

test/commander_test.rb

@@ -2,9 +2,7 @@ require "test_helper"
 
 class CommanderTest < ActiveSupport::TestCase
   setup do
-    @mrsk = Mrsk::Commander.new.tap do |mrsk|
-      mrsk.configure config_file: Pathname.new(File.expand_path("fixtures/deploy_with_roles.yml", __dir__))
-    end
+    configure_with(:deploy_with_roles)
   end
 
   test "lazy configuration" do
@@ -55,4 +53,27 @@ class CommanderTest < ActiveSupport::TestCase
     assert_equal [ "web" ], @mrsk.roles_on("1.1.1.1")
     assert_equal [ "workers" ], @mrsk.roles_on("1.1.1.3")
   end
+
+  test "default group strategy" do
+    assert_empty @mrsk.group_strategy
+  end
+
+  test "specific limit group strategy" do
+    configure_with(:deploy_with_group_strategy)
+
+    assert_equal({ in: :groups, limit: 3, wait: 2 }, @mrsk.group_strategy)
+  end
+
+  test "percentage-based group strategy" do
+    configure_with(:deploy_with_precentage_group_strategy)
+
+    assert_equal({ in: :groups, limit: 1, wait: 2 }, @mrsk.group_strategy)
+  end
+
+  private
+    def configure_with(variant)
+      @mrsk = Mrsk::Commander.new.tap do |mrsk|
+        mrsk.configure config_file: Pathname.new(File.expand_path("fixtures/#{variant}.yml", __dir__))
+      end
+    end
 end

test/fixtures/deploy_with_group_strategy.yml

@@ -14,4 +14,4 @@ registry:
 
 boot:
   group_limit: 3
-  group_wait: 30
+  group_wait: 2

test/fixtures/deploy_with_precentage_group_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:
+  group_limit: 25%
+  group_wait: 2