add ALB support

Author: yubangxi

load-balancing/elb-v2/README.md

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+# ALB and ASG lifecycle event scripts
+
+Often when running a web service, you'll have your instances behind a load balancer. But when
+deploying new code to these instances, you don't want the load balancer to continue sending customer
+traffic to an instance while the deployment is in progress. Lifecycle event scripts give you the
+ability to integrate your AWS CodeDeploy deployments with instances that are behind an ALB Target Group or
+in an Auto Scaling group. Simply set the name (or names) of the ALB Target Groups your instances are
+a part of, set the scripts in the appropriate lifecycle events, and the scripts will take care of
+deregistering the instance, waiting for connection draining, and re-registering after the deployment
+finishes.
+
+## Requirements
+
+The register and deregister scripts have a couple of dependencies in order to properly interact with
+Application Load Balancing and AutoScaling:
+
+1. The [AWS CLI](http://aws.amazon.com/cli/). In order to take advantage of
+AutoScaling's Standby feature, the CLI must be at least version 1.3.25. If you
+have Python and PIP already installed, the CLI can simply be installed with `pip
+install awscli`. Otherwise, follow the [installation instructions](http://docs.aws.amazon.com/cli/latest/userguide/installing.html)
+in the CLI's user guide.
+1. An instance profile with a policy that allows, at minimum, the following actions:
+
+```
+    elasticloadbalancing:Describe*
+    elasticloadbalancing:DeregisterTagets
+    elasticloadbalancing:RegisterTargets
+    autoscaling:Describe*
+    autoscaling:EnterStandby
+    autoscaling:ExitStandby
+    autoscaling:UpdateAutoScalingGroup
+```
+
+Note: the AWS CodeDeploy Agent requires that an instance profile be attached to all instances that
+are to participate in AWS CodeDeploy deployments. For more information on creating an instance
+profile for AWS CodeDeploy, see the [Create an IAM Instance Profile for Your Amazon EC2 Instances]()
+topic in the documentation.
+1. All instances are assumed to already have the AWS CodeDeploy Agent installed.
+
+## Installing the Scripts
+
+To use these scripts in your own application:
+
+1. Install the AWS CLI on all your instances.
+1. Update the policies on the EC2 instance profile to allow the above actions.
+1. Copy the `.sh` files in this directory into your application source.
+1. Edit your application's `appspec.yml` to run `deregister_from_elb.sh` on the ApplicationStop event,
+and `register_with_elb.sh` on the ApplicationStart event.
+1. Edit `common_functions.sh` to set `TARGET_LIST` to contain the name(s) of the Target Group your deployment group is a part of. Make sure the entries in TARGET_LIST are separated by space.
+1. Edit `common_functions.sh` to set `PORT` to the port number your application is running at (if it's different from the default port number set in Target Group)
+1. Deploy!

load-balancing/elb-v2/appspec.yml

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+version: 0.0
+os: linux
+files:
+  - source: /
+    destination: /tmp/elb-test
+hooks:
+  ApplicationStop:
+    - location: deregister_from_elb.sh
+    - location: stop_httpd.sh
+  ApplicationStart:
+    - location: start_httpd.sh
+    - location: register_with_elb.sh