Rename bluegreen_deploy -> zdd.

README.md

@@ -12,6 +12,7 @@ fast, efficient, battle-tested, highly available load balancer with many advance
  * **Real-time LB updates**, via [Marathon's event bus](https://mesosphere.github.io/marathon/docs/event-bus.html)
  * Support for Marathon's **health checks**
  * **Multi-cert TLS/SSL** support
+ * [Zero-downtime deployments](#zero-downtime-deployments)
  * Per-service **HAProxy templates**
  * DC/OS integration
  * Automated Docker image builds ([mesosphere/marathon-lb](https://hub.docker.com/r/mesosphere/marathon-lb))
@@ -156,10 +157,10 @@ Marathon-lb exposes a few endpoints on port 9090 (by default). They are:
 | Endpoint                      | Description                                                                                                                                                                                                                                                                                                               |
 |-------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
 | `:9090/haproxy?stats`         | HAProxy stats endpoint. This produces an HTML page which can be viewed in your browser, providing various statistics about the current HAProxy instance.                                                                                                                                                                  |
-| `:9090/haproxy?stats;csv`     | This is a CSV version of the stats above, which can be consumed by other tools. For example, it's used in the [`bluegreen_deploy.py`](bluegreen_deploy.py) script.                                                                                                                                                        |
+| `:9090/haproxy?stats;csv`     | This is a CSV version of the stats above, which can be consumed by other tools. For example, it's used in the [`zdd.py`](zdd.py) script.                                                                                                                                                        |
 | `:9090/_haproxy_health_check` | HAProxy health check endpoint. Returns `200 OK` if HAProxy is healthy.                                                                                                                                                                                                                                                    |
 | `:9090/_haproxy_getconfig`    | Returns the HAProxy config file as it was when HAProxy was started. Implemented in [`getconfig.lua`](getconfig.lua).                                                                                                                                                                                                      |
-| `:9090/_haproxy_getpids`      | Returns the PIDs for all HAProxy instances within the current process namespace. This literally returns `$(pidof haproxy)`. Implemented in [`getpids.lua`](getpids.lua). This is also used by the [`bluegreen_deploy.py`](bluegreen_deploy.py) script to determine if connections have finished draining during a deploy. |
+| `:9090/_haproxy_getpids`      | Returns the PIDs for all HAProxy instances within the current process namespace. This literally returns `$(pidof haproxy)`. Implemented in [`getpids.lua`](getpids.lua). This is also used by the [`zdd.py`](zdd.py) script to determine if connections have finished draining during a deploy. |
 
 
 ## HAProxy configuration
@@ -254,29 +255,31 @@ are [documented here](Longhelp.md#templates).
   < HTTP/1.1 200 OK
   ```
 
-## Zero downtime deployments
+## Zero-downtime deployments
 
 Marathon-lb is able to perform canary style blue/green deployment with zero downtime. To execute such deployments, you must follow certain patterns when using Marathon.
 
-The deployment method is described [in this Marathon document](https://mesosphere.github.io/marathon/docs/blue-green-deploy.html). Marathon-lb provides an implementation of the aforementioned deployment method with the script [`bluegreen_deploy.py`](bluegreen_deploy.py). To perform a zero downtime deploy using `bluegreen_deploy.py`, you must:
+The deployment method is described [in this Marathon document](https://mesosphere.github.io/marathon/docs/blue-green-deploy.html). Marathon-lb provides an implementation of the aforementioned deployment method with the script [`zdd.py`](zdd.py). To perform a zero downtime deploy using `zdd.py`, you must:
 
 
 - Specify the `HAPROXY_DEPLOYMENT_GROUP` and `HAPROXY_DEPLOYMENT_ALT_PORT` labels in your app template
   - `HAPROXY_DEPLOYMENT_GROUP`: This label uniquely identifies a pair of apps belonging to a blue/green deployment, and will be used as the app name in the HAProxy configuration
   - `HAPROXY_DEPLOYMENT_ALT_PORT`: An alternate service port is required because Marathon requires service ports to be unique across all apps
 - Only use 1 service port: multiple ports are not yet implemented
-- Use the provided `bluegreen_deploy.py` script to orchestrate the deploy: the script will make API calls to Marathon, and use the HAProxy stats endpoint to gracefully terminate instances
+- Use the provided `zdd.py` script to orchestrate the deploy: the script will make API calls to Marathon, and use the HAProxy stats endpoint to gracefully terminate instances
 - The marathon-lb container must be run in privileged mode (to execute `iptables` commands) due to the issues outlined in the excellent blog post by the [Yelp engineering team found here](http://engineeringblog.yelp.com/2015/04/true-zero-downtime-haproxy-reloads.html)
 - If you have long-lived TCP connections using the same HAProxy instances, it may cause the deploy to take longer than necessary. The script will wait up to 5 minutes (by default) for connections to drain from HAProxy between steps, but any long-lived TCP connections will cause old instances of HAProxy to stick around.
 
 An example minimal configuration for a [test instance of nginx is included here](tests/1-nginx.json). You might execute a deployment from a CI tool like Jenkins with:
 
 ```
-./bluegreen_deploy.py -j 1-nginx.json -m http://master.mesos:8080 -f -l http://marathon-lb.marathon.mesos:9090 --syslog-socket /dev/null
+./zdd.py -j 1-nginx.json -m http://master.mesos:8080 -f -l http://marathon-lb.marathon.mesos:9090 --syslog-socket /dev/null
 ```
 
 Zero downtime deployments are accomplished through the use of a Lua module, which reports the number of HAProxy processes which are currently running by hitting the stats endpoint at the `/_haproxy_getpids`. After a restart, there will be multiple HAProxy PIDs until all remaining connections have gracefully terminated. By waiting for all connections to complete, you may safely and deterministically drain tasks. A caveat of this, however, is that if you have any long-lived connections on the same LB, HAProxy will continue to run and serve those connections until they complete, thereby breaking this technique.
 
+The ZDD script includes the ability to specify a pre-kill hook, which is executed before draining tasks are terminated. This allows you to run your own automated checks against the old and new app before the deploy continues.
+
 ## Mesos with IP-per-task support
 
 Marathon-lb supports load balancing for applications that use the Mesos IP-per-task