Allow testing with external zookeeper

It can be handy to test against an already running zookeeper, rather
than requiring one be installed in your test environment. Allow for
that by using the NODEPOOL_ZK_HOST environment variable.

This also gives each ZKTestCase based test a pre-existing client
connection that can be used for testing. To avoid znode path conflicts,
each connection is chroot'ed under /nodepool_test/{uniqueInt}. We
attempt to remove the {uniqueInt} znode and children as part of the
test cleanup (also removed at setUp time if cleanup fails). This will
leave a single znode for /nodepool_test, but if many tests fail for
some reason, it is easier to remove a single root node rather than
potentially many of them if we do not chroot.

Change-Id: I4fd61b16353c16bed2744e0d863ce188019430cd

nodepool/tests/__init__.py

@@ -29,6 +29,7 @@ import time
 
 import fixtures
 import gear
+import kazoo.client
 import testresources
 import testtools
 
@@ -116,6 +117,24 @@ class ZookeeperServerFixture(fixtures.Fixture):
     def setUp(self):
         super(ZookeeperServerFixture, self).setUp()
 
+        if 'NODEPOOL_ZK_HOST' in os.environ:
+           if ':' in os.environ['NODEPOOL_ZK_HOST']:
+               host, port = os.environ['NODEPOOL_ZK_HOST'].split(':')
+           else:
+               host = os.environ['NODEPOOL_ZK_HOST']
+               port = None
+
+           self.zookeeper_host = host
+
+           if not port:
+               self.zookeeper_port = 2181
+           else:
+               self.zookeeper_port = int(port)
+
+           return
+
+        self.zookeeper_host = '127.0.0.1'
+
         # Get the local port range, we're going to pick one at a time
         # at random to try.
         with open('/proc/sys/net/ipv4/ip_local_port_range') as f:
@@ -500,4 +519,38 @@ class ZKTestCase(BaseTestCase):
         super(ZKTestCase, self).setUp()
         f = ZookeeperServerFixture()
         self.useFixture(f)
+        self.zookeeper_host = f.zookeeper_host
         self.zookeeper_port = f.zookeeper_port
+        self.chroot_path = "/nodepool_test/%s" % self.getUniqueInteger()
+
+        # Ensure the chroot path exists and clean up an pre-existing znodes
+        _tmp_client = kazoo.client.KazooClient(
+            hosts='%s:%s' % (self.zookeeper_host, self.zookeeper_port))
+        _tmp_client.start()
+
+        if _tmp_client.exists(self.chroot_path):
+            _tmp_client.delete(self.chroot_path, recursive=True)
+
+        _tmp_client.ensure_path(self.chroot_path)
+        _tmp_client.stop()
+
+        # Create a chroot'ed client
+        self.zkclient = kazoo.client.KazooClient(
+            hosts='%s:%s%s' % (self.zookeeper_host,
+                               self.zookeeper_port,
+                               self.chroot_path)
+        )
+        self.zkclient.start()
+
+        self.addCleanup(self._cleanup)
+
+    def _cleanup(self):
+        '''Stop the client and remove the chroot path.'''
+        self.zkclient.stop()
+
+        # Need a non-chroot'ed client to remove the chroot path
+        _tmp_client = kazoo.client.KazooClient(
+            hosts='%s:%s' % (self.zookeeper_host, self.zookeeper_port))
+        _tmp_client.start()
+        _tmp_client.delete(self.chroot_path, recursive=True)
+        _tmp_client.stop()

nodepool/tests/test_builder.py

@@ -18,7 +18,6 @@ import time
 import threading
 
 import fixtures
-import kazoo.client
 
 from nodepool import builder, exceptions, fakeprovider, tests
 
@@ -151,6 +150,4 @@ class TestNodepoolBuilder(tests.DBTestCase):
 
 class TestZookeeper(tests.ZKTestCase):
     def test_zk(self):
-        zk = kazoo.client.KazooClient(hosts='127.0.0.1:%s' % self.zookeeper_port)
-        zk.start()
-        zk.get('/')
+        self.zkclient.get('/')

tox.ini

@@ -12,6 +12,7 @@ usedevelop = True
 install_command = pip install {opts} {packages}
 deps = -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
+passenv = NODEPOOL_ZK_HOST
 commands =
   python setup.py testr --slowest --testr-args='{posargs}'