Enable rw snap mount for test debugging

Add support for using unsquashfs to uncompress the microstack snap
followed by 'snap try ./squashfs-root/'. This enables installation
of the snap as an rw mount, and local files can be modified in
./squashfs-root/ and will go live instantly. See 'snap try --help'
for more details.

New tox targets are added for snap-try, snap-try-basic, and
snap-try-cluster.

Change-Id: I54fb8dc864fd4f346f20ae986155ad36bb7c1fac

tests/framework.py

@@ -1,7 +1,7 @@
 import logging
 import json
-import unittest
 import subprocess
+import unittest
 import yaml
 
 import petname
@@ -62,6 +62,15 @@ class TestHost:
     def install_snap(self, name, options):
         self.check_output(['sudo', 'snap', 'install', name, *options])
 
+    def try_snap(self, name):
+        try:
+            self.check_output(['unsquashfs', name])
+        except subprocess.CalledProcessError:
+            logger.warning("Re-using existing squashfs-root directory with "
+                           "'snap try squashfs-root'")
+        self.check_output(['sudo', 'snap', 'try', 'squashfs-root',
+                           '--devmode'])
+
     def remove_snap(self, name, options):
         self.check_output(['sudo', 'snap', 'remove', name, *options])
 
@@ -69,13 +78,16 @@ class TestHost:
         self.check_output(['sudo', 'snap', 'connect',
                           f'{snap_name}:{plug_name}'])
 
-    def install_microstack(self, *, channel='edge', path=None):
+    def install_microstack(self, *, channel='edge', path=None, snap_try=False):
         """Install MicroStack at this host and connect relevant plugs.
         """
-        if path is not None:
+        if path and snap_try:
-            self.install_snap(path, ['--devmode'])
+            self.try_snap(path)
         else:
-            self.install_snap('microstack', [f'--{channel}', '--devmode'])
+            if path is not None:
+                self.install_snap(path, ['--devmode'])
+            else:
+                self.install_snap('microstack', [f'--{channel}', '--devmode'])
 
         # TODO: add microstack-support once it is merged into snapd.
         plugs = [

tests/test_basic.py

@@ -14,6 +14,7 @@ Web IDE.
 
 """
 
+import argparse
 import os
 import sys
 import unittest
@@ -24,6 +25,7 @@ from tests.framework import Framework  # noqa E402
 
 
 class TestBasics(Framework):
+    snap_try = False
 
     def test_basics(self):
         """Basic test
@@ -32,7 +34,8 @@ class TestBasics(Framework):
         open the Horizon GUI.
 
         """
-        self._localhost.install_microstack(path='microstack_ussuri_amd64.snap')
+        self._localhost.install_microstack(path='microstack_ussuri_amd64.snap',
+                                           snap_try=self.snap_try)
         self._localhost.init_microstack([
             '--auto',
             '--control',
@@ -100,6 +103,14 @@ class TestBasics(Framework):
 
 
 if __name__ == '__main__':
+    parser = argparse.ArgumentParser()
+    parser.add_argument("--snap-try", help="Install snap as rw mount from "
+                        "squashfs-root directory", action='store_true')
+    parser.add_argument('unittest_args', nargs='*')
+    args = parser.parse_args()
+    TestBasics.snap_try = args.snap_try
+    sys.argv[1:] = args.unittest_args
+
     # Run our tests, ignoring deprecation warnings and warnings about
     # unclosed sockets. (TODO: setup a selenium server so that we can
     # move from PhantomJS, which is deprecated, to to Selenium headless.)

tests/test_cluster.py

@@ -10,6 +10,7 @@ vms.
 
 """
 
+import argparse
 import json
 import os
 import sys
@@ -32,11 +33,13 @@ logger.addHandler(stream)
 
 
 class TestCluster(Framework):
+    snap_try = False
 
     def test_cluster(self):
         openstack_cmd = '/snap/bin/microstack.openstack'
         control_host = self._localhost
-        control_host.install_microstack(path='microstack_ussuri_amd64.snap')
+        control_host.install_microstack(path='microstack_ussuri_amd64.snap',
+                                        snap_try=self.snap_try)
 
         # Get an IP address on the lxdbr0 bridge and use it for the
         # control IP so that the tunnel ports of the compute node target the
@@ -74,7 +77,13 @@ class TestCluster(Framework):
 
         wait_addr()
 
-        compute_host.install_microstack(path='microstack_ussuri_amd64.snap')
+        if self.snap_try:
+            # Note(coreycb): Work-around for https://pad.lv/1908424
+            compute_host.check_call([
+               'sudo', 'apt', 'install', '--yes', '--allow-downgrades',
+               'snapd=2.44.3+20.04'])
+        compute_host.install_microstack(path='microstack_ussuri_amd64.snap',
+                                        snap_try=self.snap_try)
 
         # TODO add the following to args for init
         compute_host.check_call([
@@ -143,4 +152,12 @@ class TestCluster(Framework):
 
 
 if __name__ == '__main__':
+    parser = argparse.ArgumentParser()
+    parser.add_argument("--snap-try", help="Install snap as rw mount from "
+                        "squashfs-root directory", action='store_true')
+    parser.add_argument('unittest_args', nargs='*')
+    args = parser.parse_args()
+    TestCluster.snap_try = args.snap_try
+    sys.argv[1:] = args.unittest_args
+
     unittest.main(warnings='ignore')

tox.ini

@@ -30,6 +30,30 @@ commands =
     bash -c "unset http_proxy https_proxy HTTP_PROXY HTTPS_PROXY ; {toxinidir}/tests/test_basic.py"
     bash -c "unset http_proxy https_proxy HTTP_PROXY HTTPS_PROXY ; {toxinidir}/tests/test_cluster.py"
 
+[testenv:snap-try]
+# Testing environment for local debugging. Mounts rw snap from squashfs-root dir.
+commands =
+    {toxinidir}/tools/lxd_build.sh
+    flake8 {toxinidir}/tests/
+    # Specify tests in sequence, as they can't run in parallel if not
+    # using multipass.
+    bash -c "unset http_proxy https_proxy HTTP_PROXY HTTPS_PROXY ; {toxinidir}/tests/test_basic.py --snap-try"
+    bash -c "unset http_proxy https_proxy HTTP_PROXY HTTPS_PROXY ; {toxinidir}/tests/test_cluster.py --snap-try"
+
+[testenv:snap-try-basic]
+# Testing environment for local debugging. Mounts rw snap from squashfs-root dir.
+commands =
+    {toxinidir}/tools/lxd_build.sh
+    flake8 {toxinidir}/tests/
+    bash -c "unset http_proxy https_proxy HTTP_PROXY HTTPS_PROXY ; {toxinidir}/tests/test_basic.py --snap-try"
+
+[testenv:snap-try-cluster]
+# Testing environment for local debugging. Mounts rw snap from squashfs-root dir.
+commands =
+    {toxinidir}/tools/lxd_build.sh
+    flake8 {toxinidir}/tests/
+    bash -c "unset http_proxy https_proxy HTTP_PROXY HTTPS_PROXY ; {toxinidir}/tests/test_cluster.py --snap-try"
+
 [testenv:multipass]
 # Default testing environment for a human operated machine. Builds the
 # snap in a multipass instance, then runs tests in a separate multipass