Add database client

The client allows us to access any of the deployment's databases. It will be
used in the next patch to test NUMA live migration.

Original-review: https://review.rdoproject.org/r/#/c/21505/
Change-Id: Ie723aee7f12a10dd1766fda96f05987ba52e1397

requirements.txt

@@ -1,6 +1,8 @@
 # The order of packages is significant, because pip processes them in the order
 # of appearance. Changing the order has an impact on the overall integration
 # process, which may cause wedges in the gate later.
-oslo.log
 tempest
 #crudini>=0.9.3
+oslo.log
+sshtunnel
+pymysql

whitebox_tempest_plugin/config.py

@@ -78,3 +78,26 @@ nova_compute_opts = [
         help='Command to restart the nova-compute service, without any '
              'privilege management (ie, no sudo).'),
 ]
+
+database_group = cfg.OptGroup(
+    name='whitebox-database',
+    title='Config options to access the database.')
+
+database_opts = [
+    cfg.StrOpt(
+        'host',
+        help='Address of the database host. This is normally a controller.'),
+    cfg.StrOpt(
+        'internal_ip',
+        help='If the databse service is listening on separate internal '
+             'network, this option specifies its IP on that network. It will '
+             'be used to set up an SSH tunnel through the database host.'),
+    cfg.StrOpt(
+        'user',
+        help='Username to use when connecting to the database server. '
+             'This should normally be the root user, as it needs to '
+             'have permissions on all databases.'),
+    cfg.StrOpt(
+        'password',
+        help='The password to use when connecting to the database server.')
+]

whitebox_tempest_plugin/plugin.py

@@ -36,9 +36,13 @@ class WhiteboxTempestPlugin(plugins.TempestPlugin):
                                   whitebox_config.general_opts)
         config.register_opt_group(conf, whitebox_config.nova_compute_group,
                                   whitebox_config.nova_compute_opts)
+        config.register_opt_group(conf, whitebox_config.database_group,
+                                  whitebox_config.database_opts)
 
     def get_opt_lists(self):
         return [(whitebox_config.general_group.name,
                  whitebox_config.general_opts),
                 (whitebox_config.nova_compute_group.name,
-                 whitebox_config.nova_compute_opts)]
+                 whitebox_config.nova_compute_opts),
+                (whitebox_config.database_group.name,
+                 whitebox_config.database_opts)]

whitebox_tempest_plugin/services/clients.py

@@ -14,7 +14,9 @@
 #    under the License.
 
 import contextlib
+import pymysql
 from six import StringIO
+import sshtunnel
 
 from oslo_log import log as logging
 from tempest import config
@@ -182,3 +184,54 @@ class NUMAClient(SSHClient):
                     free = int(line.split(':')[1].lstrip())
             pages[node] = {'total': total, 'free': free}
         return pages
+
+
+class DatabaseClient(object):
+
+    def __init__(self):
+        self.ssh_key = CONF.whitebox.ctlplane_ssh_private_key_path
+        self.ssh_user = CONF.whitebox.ctlplane_ssh_username
+
+    @contextlib.contextmanager
+    def cursor(self, database_name, commit=False):
+        """Yields a PyMySQL cursor, tunneling to the internal subnet if
+        necessary.
+        """
+        tunnel_local_bind_host = '127.42.42.42'
+        tunnel_local_bind_port = 4242
+        if CONF.whitebox_database.internal_ip:
+            with sshtunnel.SSHTunnelForwarder(
+                    (CONF.whitebox_database.host, 3306),
+                    ssh_username=self.ssh_user,
+                    ssh_pkey=self.ssh_key,
+                    remote_bind_address=(CONF.whitebox_database.internal_ip,
+                                         3306),
+                    local_bind_address=(tunnel_local_bind_host,
+                                        tunnel_local_bind_port)):
+                conn = pymysql.connect(
+                    host=tunnel_local_bind_host, port=tunnel_local_bind_port,
+                    user=CONF.whitebox_database.user,
+                    password=CONF.whitebox_database.password,
+                    database=database_name,
+                    cursorclass=pymysql.cursors.DictCursor)
+                with conn.cursor() as c:
+                    try:
+                        yield c
+                    finally:
+                        if commit:
+                            conn.commit()
+                        conn.close()
+        else:
+            conn = pymysql.connect(
+                host=CONF.whitebox_database.host, port=3306,
+                user=CONF.whitebox_database.user,
+                password=CONF.whitebox_database.password,
+                database=database_name,
+                cursorclass=pymysql.cursors.DictCursor)
+            with conn.cursor() as c:
+                try:
+                    yield c
+                finally:
+                    if commit:
+                        conn.commit()
+                    conn.close()