Add the possibility to alter a keyspace

Based on the work of Ensighten#1

library/cassandra_alter_keyspace.py

@@ -0,0 +1,119 @@
+#!/usr/bin/python
+# -*- coding: utf-8 -*-
+# TODO: add documentation here
+try:
+    import json
+except ImportError:
+    import simplejson as json
+except:
+    json_dep_found = False
+else:
+    json_dep_found = True
+
+try:
+    from cassandra.cluster import Cluster
+    from cassandra.auth import PlainTextAuthProvider
+    from cassandra.query import dict_factory
+except ImportError:
+    cassandra_dep_found = False
+else:
+    cassandra_dep_found = True
+
+
+ALTER_KEYSPACE_FORMAT = 'ALTER KEYSPACE {keyspace} WITH REPLICATION={config} AND DURABLE_WRITES={durable_writes}'
+
+
+def alter_keyspace(module, session, keyspace, replication_strategy, durable_writes):
+    changed = True
+    reasons = []
+    cql = ALTER_KEYSPACE_FORMAT.format(keyspace=keyspace,
+                                       config=json.dumps(replication_strategy).replace('"', '\''),
+                                       durable_writes=durable_writes)
+
+    session.execute(cql)
+
+    return changed, reasons
+
+
+def main():
+
+    arg_spec = {
+        'keyspace': {
+            'type': 'str',
+            'required': True,
+        },
+        'replication_strategy': {
+            'type': 'dict',
+            'required': True,
+        },
+        'durable_writes': {
+            'type': 'bool',
+            'required': True,
+        },
+        'login_user': {
+            'type': 'str',
+            'required': True,
+        },
+        'login_password': {
+            'type': 'str',
+            'required': True,
+            'no_log': True
+        },
+        'login_hosts': {
+            'type': 'list',
+            'required': True,
+        },
+        'login_port': {
+            'type': 'int',
+            'default': 9042,
+            'required': False,
+        },
+        'protocol': {
+            'type': 'int',
+            'default': 3,
+            'required': False,
+        },
+    }
+
+    module = AnsibleModule(argument_spec=arg_spec)
+
+    keyspace = module.params['keyspace']
+    replication_strategy = module.params['replication_strategy']
+    durable_writes = module.params['durable_writes']
+    login_hosts = module.params['login_hosts']
+    login_port = module.params['login_port']
+    login_user = module.params['login_user']
+    login_password = module.params['login_password']
+    protocol = module.params['protocol']
+
+    if not cassandra_dep_found:
+        module.fail_json(msg="the python cassandra-driver module is required")
+
+    if not json_dep_found:
+        module.fail_json(msg="the python json or simplejson module is required")
+
+    try:
+        if not login_user:
+            cluster = Cluster(login_hosts, port=login_port)
+
+        else:
+            auth_provider = PlainTextAuthProvider(username=login_user,
+                                                  password=login_password)
+            cluster = Cluster(login_hosts, auth_provider=auth_provider,
+                              protocol_version=protocol, port=login_port)
+        session = cluster.connect()
+        session.row_factory = dict_factory
+    except Exception, e:
+        module.fail_json(
+            msg="unable to connect to cassandra, check login_user and " +
+                "login_password are correct. Exception message: %s"
+                % e)
+
+    changed, reasons = alter_keyspace(module, session, keyspace, replication_strategy, durable_writes)
+
+    module.exit_json(changed=changed, msg='OK', name=keyspace, reasons=reasons)
+
+# Ansible "magic" (NOQA comments tells flake8 to ignore this line since it's
+# bad Python, but required for Ansible)
+from ansible.module_utils.basic import *  # NOQA
+main()