Support customizing the primary_web_role

lib/kamal/cli/templates/deploy.yml

@@ -83,3 +83,11 @@ registry:
 # boot:
 #   limit: 10 # Can also specify as a percentage of total hosts, such as "25%"
 #   wait: 2
+
+# Configure the role used to determine the primary_web_host. This host takes
+# deploy locks, runs health checks during the deploy, and follow logs, etc.
+# This role should have traefik enabled.
+#
+# Caution: there's no support for role renaming yet, so be careful to cleanup
+#          the previous role on the deployed hosts.
+# primary_web_role: web

lib/kamal/commands/healthcheck.rb

@@ -1,7 +1,7 @@
 class Kamal::Commands::Healthcheck < Kamal::Commands::Base
 
   def run
-    web = config.role(:web)
+    web = config.role(config.primary_web_role)
 
     docker :run,
       "--detach",

lib/kamal/configuration.rb

@@ -90,13 +90,20 @@ def all_hosts
   end
 
   def primary_web_host
-    role(:web).primary_host
+    role(primary_web_role)&.primary_host
   end
 
-  def traefik_hosts
-    roles.select(&:running_traefik?).flat_map(&:hosts).uniq
+  def traefik_roles
+    roles.select(&:running_traefik?)
+  end
+
+  def traefik_role_names
+    traefik_roles.flat_map(&:name)
   end
 
+  def traefik_hosts
+    traefik_roles.flat_map(&:hosts).uniq
+  end
 
   def repository
     [ raw_config.registry["server"], image ].compact.join("/")
@@ -199,6 +206,9 @@ def asset_path
     raw_config.asset_path
   end
 
+  def primary_web_role
+    raw_config.primary_web_role || "web"
+  end
 
   def valid?
     ensure_destination_if_required && ensure_required_keys_present && ensure_valid_kamal_version
@@ -253,6 +263,14 @@ def ensure_required_keys_present
         end
       end
 
+      unless role_names.include?(primary_web_role)
+        raise ArgumentError, "The primary_web_role #{primary_web_role} isn't defined"
+      end
+
+      unless traefik_role_names.include?(primary_web_role)
+        raise ArgumentError, "Role #{primary_web_role} needs to have traefik enabled"
+      end
+
       true
     end
 

test/cli/main_test.rb

@@ -283,6 +283,16 @@ class CliMainTest < CliTestCase
     end
   end
 
+  test "config with primary web role override" do
+    run_command("config", config_file: "deploy_primary_web_role_override").tap do |output|
+      config = YAML.load(output)
+
+      assert_equal ["web_chicago", "web_tokyo"], config[:roles]
+      assert_equal ["1.1.1.1", "1.1.1.2", "1.1.1.3", "1.1.1.4"], config[:hosts]
+      assert_equal "1.1.1.3", config[:primary_host]
+    end
+  end
+
   test "config with destination" do
     run_command("config", "-d", "world", config_file: "deploy_for_dest").tap do |output|
       config = YAML.load(output)

test/configuration_test.rb

@@ -278,4 +278,29 @@ class ConfigurationTest < ActiveSupport::TestCase
     assert_nil @config.asset_path
     assert_equal "foo", Kamal::Configuration.new(@deploy.merge!(asset_path: "foo")).asset_path
   end
+
+  test "primary web role" do
+    assert_equal "web", @config.primary_web_role
+
+    config = Kamal::Configuration.new(@deploy_with_roles.deep_merge({
+      servers: { "alternate_web" => { "hosts" => [ "1.1.1.4", "1.1.1.5" ] , "traefik" => true } },
+      primary_web_role: "alternate_web" } ))
+
+    assert_equal "alternate_web", config.primary_web_role
+    assert_equal "1.1.1.4", config.primary_web_host
+  end
+
+  test "primary web role no traefik" do
+    error = assert_raises(ArgumentError) do
+      Kamal::Configuration.new(@deploy_with_roles.merge(primary_web_role: "workers"))
+    end
+    assert_match /workers needs to have traefik enabled/, error.message
+  end
+
+  test "primary web role missing" do
+    error = assert_raises(ArgumentError) do
+      Kamal::Configuration.new(@deploy.merge(primary_web_role: "bar"))
+    end
+    assert_match /bar isn't defined/, error.message
+  end
 end

test/fixtures/deploy_primary_web_role_override.yml

@@ -0,0 +1,20 @@
+service: app
+image: dhh/app
+servers:
+  web_chicago:
+    traefik: enabled
+    hosts:
+      - 1.1.1.1
+      - 1.1.1.2
+  web_tokyo:
+    traefik: enabled
+    hosts:
+      - 1.1.1.3
+      - 1.1.1.4
+env:
+  REDIS_URL: redis://x/y
+registry:
+  server: registry.digitalocean.com
+  username: user
+  password: pw
+primary_web_role: web_tokyo