Add rolling_deploy_on_docker_failure option

Author: Caleb Troughton

README.md

@@ -375,6 +375,7 @@ are the same everywhere. Settings are per-project.
    ports are not HTTP services, this allows you to only health check the ports
    that are. The default is an empty array. If you have non-HTTP services that you
    want to check, see Custom Health Checks in the previous section.
+ * `rolling_deploy_on_docker_failure` => What to do when Centurion encounters an error stopping or starting a container during a rolling deploy. By default, when an error is encountered the deploy will stop and immediately raise that error. If this option is set to `:continue` Centurion will continue deploying to the remaining hosts and raise at the end. 
 
 ###Deploy a project to a fleet of Docker servers
 

lib/tasks/deploy.rake

@@ -134,12 +134,19 @@ namespace :deploy do
   end
 
   task :rolling_deploy do
+    stop_start_errors = []
     on_each_docker_host do |server|
       service = defined_service
 
-      stop_containers(server, service, fetch(:stop_timeout, 30))
-
-      container = start_new_container(server, service, defined_restart_policy)
+      begin
+        stop_containers(server, service, fetch(:stop_timeout, 30))
+        container = start_new_container(server, service, defined_restart_policy)
+      rescue e
+        on_fail = fetch(:rolling_deploy_on_docker_failure, :exit)
+        raise e unless on_fail == :continue
+        stop_start_errors << e.message
+        next
+      end
 
       public_ports = service.public_ports - fetch(:rolling_deploy_skip_ports, [])
       public_ports.each do |port|
@@ -158,6 +165,10 @@ namespace :deploy do
 
       wait_for_load_balancer_check_interval
     end
+
+    unless stop_start_errors.empty?
+      raise stop_start_errors.join("\n")
+    end
   end
 
   task :repair do