From c225d54de1c45ca6f756a6d3c32b9341c790334a Mon Sep 17 00:00:00 2001
From: evazion <noizave@gmail.com>
Date: Wed, 7 Aug 2019 22:11:07 -0500
Subject: [PATCH] capistrano: add `deploy:rolling` task (fix #4123).

---
 config/deploy.rb                  |  3 +++
 lib/capistrano/tasks/app.rake     | 32 +++++++++++++++++++++++++++++++
 lib/capistrano/tasks/unicorn.rake |  4 ----
 lib/capistrano/tasks/web.rake     |  3 ---
 4 files changed, 35 insertions(+), 7 deletions(-)
 create mode 100644 lib/capistrano/tasks/app.rake

diff --git a/config/deploy.rb b/config/deploy.rb
index 88cebd9fd..794578a47 100644
--- a/config/deploy.rb
+++ b/config/deploy.rb
@@ -12,3 +12,6 @@ set :conditionally_migrate, true
 
 # run migrations on the primary app server
 set :migration_role, :app
+
+# how long unicorn:legacy_restart (used by deploy:rolling) waits until killing the old unicorn.
+set :unicorn_restart_sleep_time, 10
diff --git a/lib/capistrano/tasks/app.rake b/lib/capistrano/tasks/app.rake
new file mode 100644
index 000000000..1a0677fb9
--- /dev/null
+++ b/lib/capistrano/tasks/app.rake
@@ -0,0 +1,32 @@
+namespace :app do
+  set :rolling_deploy, false
+
+  before "deploy:migrate", "app:disable"
+  after "deploy:published", "app:enable"
+
+  task :disable do
+    if fetch(:rolling_deploy)
+      # do nothing
+    else
+      invoke "web:disable"
+      invoke "unicorn:terminate"
+    end
+  end
+
+  task :enable do
+    if fetch(:rolling_deploy)
+      invoke "unicorn:legacy_restart"
+    else
+      invoke "unicorn:start"
+      invoke "web:enable"
+    end
+  end
+end
+
+namespace :deploy do
+  desc "Deploy a rolling update without taking the site down for maintenance"
+  task :rolling do
+    set :rolling_deploy, true
+    invoke "deploy"
+  end
+end
diff --git a/lib/capistrano/tasks/unicorn.rake b/lib/capistrano/tasks/unicorn.rake
index 1c7e41f1b..2200dd6cb 100644
--- a/lib/capistrano/tasks/unicorn.rake
+++ b/lib/capistrano/tasks/unicorn.rake
@@ -14,7 +14,3 @@ namespace :unicorn do
     end
   end
 end
-
-after "deploy:published", "unicorn:terminate"
-after "deploy:published", "unicorn:kill"
-after "deploy:published", "unicorn:start"
diff --git a/lib/capistrano/tasks/web.rake b/lib/capistrano/tasks/web.rake
index b39eb24e8..7a4e024ad 100644
--- a/lib/capistrano/tasks/web.rake
+++ b/lib/capistrano/tasks/web.rake
@@ -19,6 +19,3 @@ namespace :web do
     end
   end
 end
-
-before "deploy:started", "web:disable"
-after "deploy:published", "web:enable"