[pytest]: Re-use DVS container when possible (sonic-net#1816)

- If the fake_platform does not change between test modules, re-use the same DVS container (but still restart it between modules and do some cleanup/re-init to ensure a consistent start state for each test module)
- Add a CLI option --force-recreate-dvs to revert to the previous behavior of creating a new DVS per test module

Signed-off-by: Lawrence Lee <[email protected]>

Author: theasianpianist

tests/conftest.py

@@ -47,13 +47,18 @@ def pytest_addoption(parser):
     parser.addoption("--dvsname",
                      action="store",
                      default=None,
-                     help="Name of a persistent DVS container to run the tests with")
+                     help="Name of a persistent DVS container to run the tests with. Mutually exclusive with --force-recreate-dvs")
 
     parser.addoption("--forcedvs",
                      action="store_true",
                      default=False,
                      help="Force tests to run in persistent DVS containers with <32 ports")
 
+    parser.addoption("--force-recreate-dvs",
+                     action="store_true",
+                     default=False,
+                     help="Force the DVS container to be recreated between each test module. Mutually exclusive with --dvsname")
+
     parser.addoption("--keeptb",
                      action="store_true",
                      default=False,
@@ -192,6 +197,9 @@ def __init__(self, ctn_name: str, pid: int, i: int):
             ensure_system(f"nsenter -t {pid} -n ip link set arp off dev {self.pifname}")
             ensure_system(f"nsenter -t {pid} -n sysctl -w net.ipv6.conf.{self.pifname}.disable_ipv6=1")
 
+    def __repr__(self):
+        return f'<VirtualServer> {self.nsname}'
+
     def kill_all_processes(self) -> None:
         pids = subprocess.check_output(f"ip netns pids {self.nsname}", shell=True).decode("utf-8")
         if pids:
@@ -339,9 +347,7 @@ def __init__(
 
             # create virtual server
             self.servers = []
-            for i in range(NUM_PORTS):
-                server = VirtualServer(self.ctn_sw.name, self.ctn_sw_pid, i)
-                self.servers.append(server)
+            self.create_servers()
 
             if self.vct:
                 self.vct_connect(newctnname)
@@ -377,13 +383,7 @@ def __init__(
         self.redis_sock = os.path.join(self.mount, "redis.sock")
         self.redis_chassis_sock = os.path.join(self.mount, "redis_chassis.sock")
 
-        # DB wrappers are declared here, lazy-loaded in the tests
-        self.app_db = None
-        self.asic_db = None
-        self.counters_db = None
-        self.config_db = None
-        self.flex_db = None
-        self.state_db = None
+        self.reset_dbs()
 
         # Make sure everything is up and running before turning over control to the caller
         self.check_ready_status_and_init_db()
@@ -392,23 +392,40 @@ def __init__(
         if buffer_model == 'dynamic':
             enable_dynamic_buffer(self.get_config_db(), self.runcmd)
 
+    def create_servers(self):
+        for i in range(NUM_PORTS):
+            server = VirtualServer(self.ctn_sw.name, self.ctn_sw_pid, i)
+            self.servers.append(server)
+            
+    def reset_dbs(self):
+        # DB wrappers are declared here, lazy-loaded in the tests
+        self.app_db = None
+        self.asic_db = None
+        self.counters_db = None
+        self.config_db = None
+        self.flex_db = None
+        self.state_db = None
+
     def destroy(self) -> None:
-        if self.appldb:
+        if getattr(self, 'appldb', False):
             del self.appldb
 
         # In case persistent dvs was used removed all the extra server link
         # that were created
         if self.persistent:
-            for s in self.servers:
-                s.destroy()
+            self.destroy_servers()
 
         # persistent and clean-up flag are mutually exclusive
         elif self.cleanup:
             self.ctn.remove(force=True)
             self.ctn_sw.remove(force=True)
             os.system(f"rm -rf {self.mount}")
-            for s in self.servers:
-                s.destroy()
+            self.destroy_servers()
+
+    def destroy_servers(self):
+        for s in self.servers:
+            s.destroy()
+        self.servers = []
 
     def check_ready_status_and_init_db(self) -> None:
         try:
@@ -423,6 +440,7 @@ def check_ready_status_and_init_db(self) -> None:
             # Initialize the databases.
             self.init_asic_db_validator()
             self.init_appl_db_validator()
+            self.reset_dbs()
 
             # Verify that SWSS has finished initializing.
             self.check_swss_ready()
@@ -451,9 +469,9 @@ def _polling_function():
 
             for pname in self.alld:
                 if process_status.get(pname, None) != "RUNNING":
-                    return (False, None)
+                    return (False, process_status)
 
-            return (process_status.get("start.sh", None) == "EXITED", None)
+            return (process_status.get("start.sh", None) == "EXITED", process_status)
 
         wait_for_result(_polling_function, service_polling_config)
 
@@ -1556,35 +1574,92 @@ def verify_vct(self):
         print("vct verifications passed ? %s" % (ret1 and ret2))
         return ret1 and ret2
 
-@pytest.yield_fixture(scope="module")
-def dvs(request) -> DockerVirtualSwitch:
+@pytest.fixture(scope="session")
+def manage_dvs(request) -> str:
+    """
+    Main fixture to manage the lifecycle of the DVS (Docker Virtual Switch) for testing
+
+    Returns:
+        (func) update_dvs function which can be called on a per-module basis
+               to handle re-creating the DVS if necessary
+    """
     if sys.version_info[0] < 3:
         raise NameError("Python 2 is not supported, please install python 3")
 
     if subprocess.check_call(["/sbin/modprobe", "team"]):
         raise NameError("Cannot install kernel team module, please install a generic kernel")
 
     name = request.config.getoption("--dvsname")
+    using_persistent_dvs = name is not None
     forcedvs = request.config.getoption("--forcedvs")
     keeptb = request.config.getoption("--keeptb")
     imgname = request.config.getoption("--imgname")
     max_cpu = request.config.getoption("--max_cpu")
     buffer_model = request.config.getoption("--buffer_model")
-    fakeplatform = getattr(request.module, "DVS_FAKE_PLATFORM", None)
-    log_path = name if name else request.module.__name__
+    force_recreate = request.config.getoption("--force-recreate-dvs")
+    dvs = None
+    curr_fake_platform = None   # lgtm[py/unused-local-variable]
+
+    if using_persistent_dvs and force_recreate:
+        pytest.fail("Options --dvsname and --force-recreate-dvs are mutually exclusive")
+
+    def update_dvs(log_path, new_fake_platform=None):
+        """
+        Decides whether or not to create a new DVS
+
+        Create a new the DVS in the following cases:
+        1. CLI option `--force-recreate-dvs` was specified (recreate for every module)
+        2. The fake_platform has changed (this can only be set at container creation,
+           so it is necessary to spin up a new DVS)
+        3. No DVS currently exists (i.e. first time startup)
+
+        Otherwise, restart the existing DVS (to get to a clean state)
+
+        Returns:
+            (DockerVirtualSwitch) a DVS object
+        """
+        nonlocal curr_fake_platform, dvs
+        if force_recreate or \
+           new_fake_platform != curr_fake_platform or \
+           dvs is None:
 
-    dvs = DockerVirtualSwitch(name, imgname, keeptb, fakeplatform, log_path, max_cpu, forcedvs, buffer_model = buffer_model)
+            if dvs is not None:
+                dvs.get_logs()
+                dvs.destroy()
 
-    yield dvs
+            dvs = DockerVirtualSwitch(name, imgname, keeptb, new_fake_platform, log_path, max_cpu, forcedvs, buffer_model = buffer_model)
+
+            curr_fake_platform = new_fake_platform
+
+        else:
+            # First generate GCDA files for GCov
+            dvs.runcmd('killall5 -15')
+            # If not re-creating the DVS, restart container
+            # between modules to ensure a consistent start state
+            dvs.net_cleanup()
+            dvs.destroy_servers()
+            dvs.create_servers()
+            dvs.restart()
+
+        return dvs
+
+    yield update_dvs
 
     dvs.get_logs()
     dvs.destroy()
 
-    # restore original config db
     if dvs.persistent:
         dvs.runcmd("mv /etc/sonic/config_db.json.orig /etc/sonic/config_db.json")
         dvs.ctn_restart()
 
+@pytest.yield_fixture(scope="module")
+def dvs(request, manage_dvs) -> DockerVirtualSwitch:
+    fakeplatform = getattr(request.module, "DVS_FAKE_PLATFORM", None)
+    name = request.config.getoption("--dvsname")
+    log_path = name if name else request.module.__name__
+
+    return manage_dvs(log_path, fakeplatform)
+
 @pytest.yield_fixture(scope="module")
 def vct(request):
     vctns = request.config.getoption("--vctns")

tests/dvslib/dvs_common.py

@@ -56,7 +56,7 @@ def wait_for_result(
         time.sleep(polling_config.polling_interval)
 
     if polling_config.strict:
-        message = failure_message or f"Operation timed out after {polling_config.timeout} seconds"
+        message = failure_message or f"Operation timed out after {polling_config.timeout} seconds with result {result}"
         assert False, message
 
     return (False, result)