fix: allow configurations without web roles

lib/kamal/cli/healthcheck.rb

@@ -3,6 +3,7 @@ class Kamal::Cli::Healthcheck < Kamal::Cli::Base
 
   desc "perform", "Health check current app version"
   def perform
+    return unless KAMAL.primary_role.running_traefik?
     on(KAMAL.primary_host) do
       begin
         execute *KAMAL.healthcheck.run

lib/kamal/commander.rb

@@ -24,7 +24,7 @@ class Kamal::Commander
   attr_reader :specific_roles, :specific_hosts
 
   def specific_primary!
-    self.specific_hosts = [ config.primary_web_host ]
+    self.specific_hosts = [ config.primary_host ]
   end
 
   def specific_roles=(role_names)
@@ -36,7 +36,7 @@ class Kamal::Commander
   end
 
   def primary_host
-    specific_hosts&.first || specific_roles&.first&.primary_host || config.primary_web_host
+    specific_hosts&.first || specific_roles&.first&.primary_host || config.primary_host
   end
 
   def primary_role

lib/kamal/commands/healthcheck.rb

@@ -2,6 +2,7 @@ class Kamal::Commands::Healthcheck < Kamal::Commands::Base
 
   def run
     web = config.role(:web)
+    return unless web.present?
 
     docker :run,
       "--detach",

lib/kamal/configuration.rb

@@ -89,8 +89,12 @@ class Kamal::Configuration
     roles.flat_map(&:hosts).uniq
   end
 
-  def primary_web_host
-    role(:web).primary_host
+  def primary_host
+    primary_role.primary_host
+  end
+
+  def primary_role
+    role(:web) || roles.first
   end
 
   def traefik_hosts
@@ -208,7 +212,7 @@ class Kamal::Configuration
     {
       roles: role_names,
       hosts: all_hosts,
-      primary_host: primary_web_host,
+      primary_host: primary_host,
       version: version,
       repository: repository,
       absolute_image: absolute_image,