Add functions to set/unset upgrade_levels for compute service

These functions set and unset upgrade_levels for the compute service
in nova.conf file. It will be used to handle rolling upgrade of compute
nodes as well as the cleanup of nova.conf once upgrade is finished.

Related-bug: #1506041
Co-Authored-By: Ilya Kharin <akscram@gmail.com>
Change-Id: I4fcefae2051221ad220c0cb70226083060c5aa23

octane/magic_consts.py

@@ -27,3 +27,11 @@ BRIDGES = ['br-ex', 'br-mgmt']
 DEFAULT_DISKS = True
 DEFAULT_NETS = True
 ISCSI_CONFIG_PATH = "/etc/iscsi/initiatorname.iscsi"
+VERSIONS = {
+    '7.0': 'kilo',
+    '6.1': 'juno',
+    '6.0': 'juno',
+    '5.2.9': 'icehouse',
+    '5.1.1': 'icehouse',
+    '5.1': 'icehouse',
+}

octane/tests/test_util_node.py

@@ -10,6 +10,7 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
+import contextlib
 import io
 import mock
 import pytest
@@ -96,3 +97,47 @@ def test_untar_files(node, mock_ssh_popen, mock_open):
                                            stdin=ssh.PIPE, node=node)
     mock_open.assert_called_once_with('filename', 'rb')
     assert buf.getvalue() == content
+
+
+@contextlib.contextmanager
+def _check_upgrade_levels(mocker, node, content, expected_content):
+    mock_sftp = mocker.patch('octane.util.ssh.sftp')
+
+    old = io.BytesIO(content)
+    mock_new = mocker.Mock()
+    buf = io.BytesIO()
+    mock_new.write = buf.write
+    mock_update_file = mocker.patch('octane.util.ssh.update_file')
+    mock_update_file.return_value.__enter__.return_value = (old, mock_new)
+
+    yield
+
+    mock_sftp.assert_called_once_with(node)
+    mock_update_file.assert_called_once_with(mock_sftp.return_value,
+                                             '/etc/nova/nova.conf')
+    assert buf.getvalue() == expected_content
+
+
+NOVA_DEFAULT = b"#\u0444\n[DEFAULT]\ndebug = True\n"
+NOVA_WITH_EMPTY_LEVELS = NOVA_DEFAULT + b"[upgrade_levels]\n"
+NOVA_WITH_KILO_LEVELS = NOVA_WITH_EMPTY_LEVELS + b"compute=kilo\n"
+
+
+@pytest.mark.parametrize("content,expected_content", [
+    (NOVA_DEFAULT, NOVA_DEFAULT),
+    (NOVA_WITH_EMPTY_LEVELS, NOVA_WITH_KILO_LEVELS),
+])
+def test_add_compute_upgrade_levels(mocker, node, content, expected_content):
+    with _check_upgrade_levels(mocker, node, content, expected_content):
+        node_util.add_compute_upgrade_levels(node, 'kilo')
+
+
+@pytest.mark.parametrize("content,expected_content", [
+    (NOVA_DEFAULT, NOVA_DEFAULT),
+    (NOVA_WITH_EMPTY_LEVELS, NOVA_WITH_EMPTY_LEVELS),
+    (NOVA_WITH_KILO_LEVELS, NOVA_WITH_EMPTY_LEVELS),
+])
+def test_remove_compute_upgrade_levels(mocker, node, content,
+                                       expected_content):
+    with _check_upgrade_levels(mocker, node, content, expected_content):
+        node_util.remove_compute_upgrade_levels(node)

octane/util/node.py

@@ -119,3 +119,21 @@ def wait_for_mcollective_start(nodes, timeout=600):
             raise Exception("Timeout waiting for nodes {0} to start"
                             " mcollective".format(failed))
         wait_list -= done
+
+
+def add_compute_upgrade_levels(node, version):
+    sftp = ssh.sftp(node)
+    with ssh.update_file(sftp, '/etc/nova/nova.conf') as (old, new):
+        for line in old:
+            new.write(line)
+            if line.startswith("[upgrade_levels]"):
+                new.write("compute={0}\n".format(version))
+
+
+def remove_compute_upgrade_levels(node):
+    sftp = ssh.sftp(node)
+    with ssh.update_file(sftp, '/etc/nova/nova.conf') as (old, new):
+        for line in old:
+            if line.startswith("compute="):
+                continue
+            new.write(line)