Halt Deploys With release script if ENV variable DEPLOY_STATUS is set…

… to blocked (forem#5510) [deploy]

docs/deployment.md

@@ -37,13 +37,20 @@ Upon deploy, the app installs dependencies, bundles assets, and gets the app
 ready for launch. However, before it launches and releases the app Heroku runs a
 release script on a one-off dyno. If that release script/step succeeds the new
 app is released on all of the dynos. If that release script/step fails then the
-deploy is halted and we are notified. During this release step, we first run any
-outstanding migrations. This ensures that a migration finishes successfully
-before the code that uses it goes live. After running migrations, we use the
-rails runner to output a simple string. Executing a Rails runner command allows
-us to ensure that we can boot up the entire app successfully before it is
-deployed. We deploy asynchronously, so the website is running the new code a few
-minutes after deploy. A new instance of Heroku Rails console will immediately
-run a new code.
+deploy is halted and we are notified. During this release step, we first check
+the DEPLOY_STATUS environment variable. In the event that we want to prevent
+deploys, for example after a rollback, we will set DEPLOY_STATUS to "blocked".
+This will cause the release script to exit with a code of 1 which will halt the
+deploy. This ensures that we don't accidentally push out code while we are
+waiting for a fix or running other tasks. Next, we run any outstanding
+migrations. This ensures that a migration finishes successfully before the code
+that uses it goes live. After running migrations, we use the Rails runner to
+output a simple string. Executing a Rails runner command ensures that we can
+boot up the entire app successfully before it is deployed. We deploy
+asynchronously, so the website is running the new code a few minutes after
+deploy. A new instance of Heroku Rails console will immediately run a new code.
+We deploy asynchronously, so the website is running the new code a few minutes
+after deploy. A new instance of Heroku Rails console will immediately run a new
+code.
 
 ![](https://devcenter0.assets.heroku.com/article-images/1494371187-release-phase-diagram-3.png)

release-tasks.sh

@@ -1,3 +1,11 @@
 #!/bin/bash
 
-STATEMENT_TIMEOUT=180000 bundle exec rails db:migrate && rails runner "puts 'app load success'"
+# enable echo mode
+set -x
+
+# abort release if deploy status equals "blocked"
+[[ $DEPLOY_STATUS = "blocked" ]] && echo "Deploy blocked" && exit 1
+
+# runs migration and boots the app to check there are no errors
+STATEMENT_TIMEOUT=180000 bundle exec rails db:migrate && \
+  bundle exec rails runner "puts 'app load success'"