added hautoproxy auto-configuring haproxy

This image configures haproxy to forward connections for all available
kubernetes services.  It is meant to be run alongside other contains in
a kubernetes pod to provide access to "remote" services at a consistent
address so that keystone api endpoints can be configured in a sane
fashion.

Change-Id: Ic923c6a772f1bdf36b97b05a1d04de9e5b841ddd

docker/hautoproxy/Dockerfile

@@ -0,0 +1,8 @@
+FROM fedora
+
+RUN yum -y install haproxy python-jinja2; yum clean all
+RUN mkdir -p /etc/haproxy/templates
+ADD haproxy.cfg.tmpl /etc/haproxy/templates/haproxy.cfg.tmpl
+ADD start.py /start.py
+CMD ["/start.py"]
+

docker/hautoproxy/build

@@ -0,0 +1 @@
+../../tools/build-docker-image

docker/hautoproxy/haproxy.cfg.tmpl

@@ -0,0 +1,26 @@
+global
+    daemon
+    maxconn 4096
+    pidfile /var/run/haproxy.pid
+
+defaults
+    mode tcp
+    timeout connect 5s
+    timeout client 1m
+    timeout server 1m
+    option redispatch
+    balance roundrobin
+
+listen stats :1936
+    mode http
+    stats enable
+    stats hide-version
+    #stats realm Haproxy\ Statistics
+    stats uri /
+    #stats auth Username:Password
+
+{% for service in services %}
+listen {{ service.service_name }}
+    bind 127.0.0.1:{{service.local_port}}
+    server {{ service.remote_name }} {{ service.remote_addr }}:{{ service.remote_port}} check inter 2s rise 3 fall 2
+{% endfor %}

docker/hautoproxy/start.py

@@ -0,0 +1,65 @@
+#!/usr/bin/python
+
+'''This script configures and starts a local haproxy instances, bound to
+127.0.0.1, that forwards connections all of the discovered
+docker/kubernetes environment variables.'''
+
+import argparse
+import os
+import sys
+from jinja2 import Environment, FileSystemLoader
+import re
+import urlparse
+
+re_url = re.compile(
+    '^(?P<name>.*)_PORT_(?P<port>\d+)_(?P<proto>(UDP|TCP))$')
+
+def parse_args():
+    p = argparse.ArgumentParser()
+    p.add_argument('--output', '-o',
+                   default='/etc/haproxy/haproxy.cfg')
+    p.add_argument('--no-start', '-n',
+                   action='store_true')
+    p.add_argument('--template-dir', '-t',
+                   default='/etc/haproxy/templates')
+    return p.parse_args()
+
+def discover_services():
+    services = []
+    for k in os.environ:
+        mo = re_url.match(k)
+
+        if mo:
+            parts = urlparse.urlparse(os.environ[k])
+            remote_host,remote_port = parts.netloc.split(':')
+            service_name = '%(name)s-%(port)s' % mo.groupdict()
+
+            services.append({
+                'remote_name': mo.group('name'),
+                'remote_addr': remote_host,
+                'remote_port': remote_port,
+                'remote_proto': parts.scheme,
+                'local_port': mo.group('port'),
+                'service_name': service_name,
+            })
+
+    return services
+
+def main():
+    args = parse_args()
+    services = discover_services()
+
+    env = Environment(loader=FileSystemLoader(['.',
+                                               args.template_dir]))
+    template = env.get_template('haproxy.cfg.tmpl')
+    with open(args.output, 'w') as fd:
+        fd.write(template.render(services=services))
+
+    if args.no_start:
+        return
+
+    os.execlp('haproxy', 'haproxy', '-f', args.output, '-db')
+
+if __name__ == '__main__':
+    main()
+