Merge pull request #19 from AssemblyAI/add-blue-green-support

Add blue green support

.env.example

@@ -2,4 +2,12 @@ export PLUGIN_AWS_REGION=us-east-2
 export PLUGIN_SERVICE=
 export PLUGIN_CLUSTER=
 export PLUGIN_CONTAINER=
-export PLUGIN_IMAGE=
+export PLUGIN_IMAGE=
+export PLUGIN_MODE=
+export PLUGIN_BLUE_SERVICE=
+export PLUGIN_GREEN_SERVICE=
+export PLUGIN_MAX_DEPLOY_CHECKS=
+export PLUGIN_SCALE_DOWN_PERCENT=
+export PLUGIN_SCALE_DOWN_INTERVAL=
+export PLUGIN_SCALE_DOWN_WAIT_PERIOD=
+export PLUGIN_CHECKS_TO_PASS=

README.md

@@ -4,17 +4,20 @@
 
 `drone-deploy-ecs` is an opinionated Drone plugin for updating a single container within an ECS Task.
 
-During deployment, the plugin retrieves the active Task Definition for a specified ECS Service, creates a new revision of the Task Definition with an updated image for a specified container, updates the Service to use the new Task Definition, and waits for the deployment to complete.
+This plugin has support for two deployment modes: rolling and blue / green.
+
+During a rolling deployment, the plugin retrieves the active Task Definition for a specified ECS Service, creates a new revision of the Task Definition with an updated image for a specified container, updates the Service to use the new Task Definition, and waits for the deployment to complete.
+
+A blue / green deployment is similar to a rolling deployment. The key difference is that once the number of running green tasks matches the number of desired green tasks, the blue service is scaled down. It's important to note that this plugin _only_ uses desired vs running to determine deployment health. It will not check the health of a target in a target group, for example
 
 [ECR Link](https://gallery.ecr.aws/assemblyai/drone-deploy-ecs)
 
 ## Important Notes
 
-This plugin cannot update different containers within the same Task Definition simultaneously. It will only update the image for a single container within a Task Defintion
+This plugin cannot update multiple containers within the same Task Definition simultaneously. It will only update the image for a single container within a Task Defintion
 
 The ECS Service must use the `ECS` deployment controller.
 
-~~This plugin will not rollback for you. For rollbacks, use a [deployment circuit breaker](https://aws.amazon.com/blogs/containers/announcing-amazon-ecs-deployment-circuit-breaker/).~~
 
 ## Requirements
 
@@ -28,10 +31,13 @@ The ECS Service being deployed to must use the `ECS` deployment controller.
 - `ecs:DescribeServices` on any services this tool will modify
 - `ecs:UpdateService` on any services this tool will modify 
 - `ecs:RegisterTaskDefinition` on `*`
-
+- `application-autoscaling:DescribeScalableTargets` on `*`
+- `application-autoscaling:RegisterScalableTarget` on `*` if you plan on using a blue/green deployment
 
 ## Example usage
 
+### Rolling Deployment
+
 ```yaml
 ---
 kind: pipeline
@@ -41,6 +47,7 @@ steps:
 - name: deploy
   image: public.ecr.aws/assemblyai/drone-deploy-ecs
   settings:
+    mode: rolling
     aws_region: us-east-2
     # The name of the ECS service
     service: webapp
@@ -51,4 +58,59 @@ steps:
     # The image to deploy
     image: myorg/nginx-${DRONE_COMMIT_SHA}
     max_deploy_checks: 10
-```
+```
+
+### Blue / Green
+
+Blue / Green deployments will work with services that use Application Autoscaling and those that do not.
+
+One service must have a desired count of 0, the other must have a desired count > 0.
+
+It does not matter which service is set for `blue_service` or `green_service`. The plugin will use the service with a desired count of 0 as the green service. This is simply a way to define which two services the plugin should modify. 
+
+Once the number of running containers equals the number of desired containers for the green service, the plugin will begin scaling down the blue service by  `scale_down_percent`. 
+
+
+```yml
+---
+kind: pipeline
+name: deploy
+
+steps:
+- name: deploy
+  image: public.ecr.aws/assemblyai/drone-deploy-ecs
+  settings:
+    mode: blue-green
+    aws_region: us-east-2
+    # The name of the green ECS service
+    green_service: webapp-green
+    # The name of the blue ECS service
+    blue_service: webapp-blue
+    # The name of the ECS cluster that the service is in
+    cluster: dev-ecs-cluster
+    # The name of the container to update
+    container: nginx
+    # The image to deploy
+    image: myorg/nginx-${DRONE_COMMIT_SHA}
+    # How many times to check rollout status before failing
+    max_deploy_checks: 10
+    # Percent of instances to scale down blue service by
+    scale_down_percent: 50
+    # Seconds to wait between scale down events
+    scale_down_interval: 600
+    # Number of seconds between scaling up green service and scaling down blue
+    # This is useful if your application takes some time to become healthy
+    scale_down_wait_period: 10
+    # Number of times running count must equal desired count in order to mark green deployment as a success
+    checks_to_pass: 2
+```
+
+
+## TODO
+
+- Code cleanup
+- Better `settings` documentation
+- Tests
+- Better, more consistent logging
+- Update `pkg/deploy` functions to use `deploy.DeployConfig`
+- Fix `scaleDownInPercentages()` bug