feat(controller): add hostname exposing to units

This exposes a configurable hostname type to Docker container through
fleet unit files.

Three hostname types are supported:
- default     : standard Docker hostname
- application : application hostname (e.g. my-app.v54.web.1)
- server      : Core OS hostname

This fixes #2835 and is an alternative to #2428, which got rejected.

It is necessary when using a monitoring solution like New Relic.

Author: Arne-Christian Blystad

controller/bin/boot

@@ -49,6 +49,7 @@ etcd_set_default secretKey ${DEIS_SECRET_KEY:-`openssl rand -base64 64 | tr -d '
 etcd_set_default builderKey ${DEIS_BUILDER_KEY:-`openssl rand -base64 64 | tr -d '\n'`}
 etcd_set_default registrationEnabled 1
 etcd_set_default webEnabled 0
+etcd_set_default unitHostname default
 
 # safely create required keyspaces
 etcd_safe_mkdir /deis/services

controller/deis/settings.py

@@ -308,6 +308,13 @@
 # see https://docs.djangoproject.com/en/1.6/ref/settings/#secure-proxy-ssl-header
 SECURE_PROXY_SSL_HEADER = ('HTTP_X_FORWARDED_PROTO', 'https')
 
+# Unit Hostname handling.
+# Supports:
+#  default      - Docker generated hostname
+#  application  - Hostname based on application unit name (i.e. my-application.v2.web.1)
+#  server       - Hostname based on CoreOS server hostname
+UNIT_HOSTNAME = 'default'
+
 # Create a file named "local_settings.py" to contain sensitive settings data
 # such as database configuration, admin email, or passwords and keys. It
 # should also be used for any settings which differ between development

controller/scheduler/fleet.py

@@ -7,6 +7,7 @@
 import socket
 import re
 import time
+from django.conf import settings
 
 
 MATCH = re.compile(
@@ -112,6 +113,8 @@ def _create_container(self, name, image, command, unit, **kwargs):
             l.update({'cpu': '-c {}'.format(cpu)})
         else:
             l.update({'cpu': ''})
+        # set unit hostname
+        l.update({'hostname': self._get_hostname(name)})
         # should a special entrypoint be used
         entrypoint = kwargs.get('entrypoint')
         if entrypoint:
@@ -137,6 +140,19 @@ def _create_container(self, name, image, command, unit, **kwargs):
                 if attempt == (RETRIES - 1):  # account for 0 indexing
                     raise
 
+    def _get_hostname(self, application_name):
+        hostname = settings.UNIT_HOSTNAME
+        if hostname == "default":
+            return ''
+        elif hostname == "application":
+            # replace underscore with dots, since underscore is not valid in DNS hostnames
+            dns_name = application_name.replace("_", ".")
+            return '-h ' + dns_name
+        elif hostname == "server":
+            return '-h %H'
+        else:
+            raise RuntimeError('Unsupported hostname: ' + hostname)
+
     def start(self, name):
         """Start a container"""
         self._wait_for_container(name)
@@ -294,7 +310,7 @@ def attach(self, name):
     {"section": "Unit", "name": "Description", "value": "{name}"},
     {"section": "Service", "name": "ExecStartPre", "value": '''/bin/sh -c "IMAGE=$(etcdctl get /deis/registry/host 2>&1):$(etcdctl get /deis/registry/port 2>&1)/{image}; docker pull $IMAGE"'''},  # noqa
     {"section": "Service", "name": "ExecStartPre", "value": '''/bin/sh -c "docker inspect {name} >/dev/null 2>&1 && docker rm -f {name} || true"'''},  # noqa
-    {"section": "Service", "name": "ExecStart", "value": '''/bin/sh -c "IMAGE=$(etcdctl get /deis/registry/host 2>&1):$(etcdctl get /deis/registry/port 2>&1)/{image}; port=$(docker inspect -f '{{{{range $k, $v := .ContainerConfig.ExposedPorts }}}}{{{{$k}}}}{{{{end}}}}' $IMAGE | cut -d/ -f1) ; docker run --name {name} {memory} {cpu} -P -e PORT=$port $IMAGE {command}"'''},  # noqa
+    {"section": "Service", "name": "ExecStart", "value": '''/bin/sh -c "IMAGE=$(etcdctl get /deis/registry/host 2>&1):$(etcdctl get /deis/registry/port 2>&1)/{image}; port=$(docker inspect -f '{{{{range $k, $v := .ContainerConfig.ExposedPorts }}}}{{{{$k}}}}{{{{end}}}}' $IMAGE | cut -d/ -f1) ; docker run --name {name} {memory} {cpu} {hostname} -P -e PORT=$port $IMAGE {command}"'''},  # noqa
     {"section": "Service", "name": "ExecStop", "value": '''/usr/bin/docker rm -f {name}'''},
     {"section": "Service", "name": "TimeoutStartSec", "value": "20m"},
     {"section": "Service", "name": "RestartSec", "value": "5"},

controller/templates/confd_settings.py

@@ -44,3 +44,5 @@
 {{ if .deis_controller_webEnabled }}
 WEB_ENABLED = bool({{ .deis_controller_webEnabled }})
 {{ end }}
+
+UNIT_HOSTNAME = '{{ or (.deis_controller_unitHostname) "default" }}'