Adds ulimit to the docker module

The ulimit will be specified as a list and separated by colons. The
hard limit is optional, in which case it is equal to the soft limit.

The ulimits are compared to the ulimits of the container and added
or adjusted accordingly on by a reload.

The module ensures that ulimits are available in the capabilities
iff ulimits is passes as a parameter.

cloud/docker/docker.py

@@ -370,6 +370,14 @@ options:
     required: false
     default: 0
     version_added: "2.1"
+  ulimits:
+    description:
+      - ulimits, list ulimits with name, soft and optionally
+        hard limit separated by colons. e.g. nofile:1024:2048
+        Requires docker-py >= 1.2.0 and docker >= 1.6.0
+    required: false
+    default: null
+    version_added: "2.1"
 
 author:
     - "Cove Schneider (@cove)"
@@ -378,6 +386,7 @@ author:
     - "Ash Wilson (@smashwilson)"
     - "Thomas Steinbach (@ThomasSteinbach)"
     - "Philippe Jandot (@zfil)"
+    - "Daan Oosterveld (@dusdanig)
 requirements:
     - "python >= 2.6"
     - "docker-py >= 0.3.0"
@@ -660,6 +669,7 @@ class DockerManager(object):
             'read_only': ((1, 0, 0), '1.17'),
             'labels': ((1, 2, 0), '1.18'),
             'stop_timeout': ((0, 5, 0), '1.0'),
+            'ulimits': ((1, 2, 0), '1.18'),
             # Clientside only
             'insecure_registry': ((0, 5, 0), '0.0')
             }
@@ -714,6 +724,19 @@ class DockerManager(object):
 
         self.env = self.module.params.get('env', None)
 
+        self.ulimits = None
+        if self.module.params.get('ulimits'):
+            self.ulimits = []
+            ulimits = self.module.params.get('ulimits')
+            for ulimit in ulimits:
+                parts = ulimit.split(":")
+                if len(parts) == 2:
+                    self.ulimits.append({'name': parts[0], 'soft': int(parts[1]), 'hard': int(parts[1])})
+                elif len(parts) == 3:
+                    self.ulimits.append({'name': parts[0], 'soft': int(parts[1]), 'hard': int(parts[2])})
+                else:
+                    self.module.fail_json(msg='ulimits support 2 to 3 arguments')
+
         # Connect to the docker server using any configured host and TLS settings.
 
         env_host = os.getenv('DOCKER_HOST')
@@ -1165,6 +1188,16 @@ class DockerManager(object):
                 differing.append(container)
                 continue
 
+            # ULIMITS
+
+            expected_ulimit_keys = set(map(lambda x: '%s:%s:%s' % (x['name'],x['soft'],x['hard']), self.ulimits or []))
+            actual_ulimit_keys = set(map(lambda x: '%s:%s:%s' % (x['Name'],x['Soft'],x['Hard']), (container['HostConfig']['Ulimits'] or [])))
+
+            if actual_ulimit_keys != expected_ulimit_keys:
+                self.reload_reasons.append('ulimits ({0} => {1})'.format(actual_ulimit_keys, expected_ulimit_keys))
+                differing.append(container)
+                continue
+
             # CPU_SHARES
 
             expected_cpu_shares = self.module.params.get('cpu_shares')
@@ -1566,6 +1599,9 @@ class DockerManager(object):
         else:
             params['host_config']['Memory'] = mem_limit
 
+        if self.ulimits is not None:
+            self.ensure_capability('ulimits')
+            params['host_config']['ulimits'] = self.ulimits
 
         def do_create(count, params):
             results = []
@@ -1813,6 +1849,7 @@ def main():
             labels          = dict(default={}, type='dict'),
             stop_timeout    = dict(default=10, type='int'),
             timeout         = dict(required=False, default=DEFAULT_TIMEOUT_SECONDS, type='int'),
+            ulimits         = dict(default=None, type='list'),
         ),
         required_together = (
             ['tls_client_cert', 'tls_client_key'],