Allow workers to send back metadata

To help with debugging, allow workers to send back information about
itself such as hostname and ips. This will allow for an RPC/Client
call to get the information on running jobs.

Change-Id: I03b553293923cd65b3a9651a8877aa23688d2909
diff --git a/doc/source/launchers.rst b/doc/source/launchers.rst
index c56d6e9..db49933 100644
--- a/doc/source/launchers.rst
+++ b/doc/source/launchers.rst
@@ -87,8 +87,8 @@
 **ZUUL_PIPELINE**
   The Zuul pipeline that is building this job
 **ZUUL_URL**
-  The url for the zuul server as configured in zuul.conf.  
-  A test runner may use this URL as the basis for fetching 
+  The url for the zuul server as configured in zuul.conf.
+  A test runner may use this URL as the basis for fetching
   git commits.
 
 The following additional parameters will only be provided for builds
@@ -195,6 +195,30 @@
   The URL with the status or results of the build.  Will be used in
   the status page and the final report.
 
+To help with debugging builds a worker may send back some optional
+metadata:
+
+**worker_name** (optional)
+  The name of the worker.
+
+**worker_hostname** (optional)
+  The hostname of the worker.
+
+**worker_ips** (optional)
+  A list of IPs for the worker.
+
+**worker_fqdn** (optional)
+  The FQDN of the worker.
+
+**worker_program** (optional)
+  The program name of the worker. For example Jenkins or turbo-hipster.
+
+**worker_version** (optional)
+  The version of the software running the job.
+
+**worker_extra** (optional)
+  A dictionary of any extra metadata you may want to pass along.
+
 It should then immediately send a WORK_STATUS packet with a value of 0
 percent complete.  It may then optionally send subsequent WORK_STATUS
 packets with updated completion values.