Ensure that UUID is retrieved from database on workflow restart.

cylc/flow/scheduler.py

@@ -282,7 +282,6 @@ def __init__(self, id_: str, options: Values) -> None:
             workflow=self.workflow,
         )
         self.id = self.tokens.id
-        self.uuid_str = str(uuid4())
         self.options = options
         self.template_vars = get_template_vars(self.options)
 
@@ -307,6 +306,7 @@ def __init__(self, id_: str, options: Values) -> None:
             pub_d=os.path.join(self.workflow_run_dir, 'log')
         )
         self.is_restart = Path(self.workflow_db_mgr.pri_path).is_file()
+
         # Map used to track incomplete remote inits for restart
         # {install_target: platform}
         self.incomplete_ri_map: Dict[str, Dict] = {}
@@ -394,7 +394,6 @@ async def initialise(self):
             self.bad_hosts,
             self.reset_inactivity_timer
         )
-        self.task_events_mgr.uuid_str = self.uuid_str
 
         self.task_job_mgr = TaskJobManager(
             self.workflow,
@@ -404,11 +403,10 @@ async def initialise(self):
             self.data_store_mgr,
             self.bad_hosts
         )
-        self.task_job_mgr.task_remote_mgr.uuid_str = self.uuid_str
 
         self.profiler = Profiler(self, self.options.profile_mode)
 
-    async def configure(self):
+    async def configure(self, params):
         """Configure the scheduler.
 
         * Load the flow configuration.
@@ -426,7 +424,7 @@ async def configure(self):
         self._check_startup_opts()
 
         if self.is_restart:
-            self.load_workflow_params_and_tmpl_vars()
+            self._set_workflow_params(params)
 
         self.profiler.log_memory("scheduler.py: before load_flow_file")
         try:
@@ -549,15 +547,6 @@ async def configure(self):
 
         self.profiler.log_memory("scheduler.py: end configure")
 
-    def load_workflow_params_and_tmpl_vars(self) -> None:
-        """Load workflow params and template variables"""
-        with self.workflow_db_mgr.get_pri_dao() as pri_dao:
-            # This logic handles lack of initial cycle point in flow.cylc and
-            # things that can't change on workflow restart/reload.
-            self._load_workflow_params(pri_dao.select_workflow_params())
-            pri_dao.select_workflow_template_vars(self._load_template_vars)
-            pri_dao.execute_queued_items()
-
     def log_start(self) -> None:
         """Log headers, that also get logged on each rollover.
 
@@ -696,12 +685,26 @@ async def run_scheduler(self) -> None:
         finally:
             self.profiler.stop()
 
+    def load_workflow_params_and_tmpl_vars(self) -> List[Tuple[str, str]]:
+        """Load workflow params and template variables"""
+        with self.workflow_db_mgr.get_pri_dao() as pri_dao:
+            # This logic handles lack of initial cycle point in flow.cylc and
+            # things that can't change on workflow restart/reload.
+            pri_dao.select_workflow_template_vars(self._load_template_vars)
+            pri_dao.execute_queued_items()
+            return list(pri_dao.select_workflow_params())
+
     async def start(self):
         """Run the startup sequence but don't set the main loop running.
 
         Lightweight wrapper for testing convenience.
 
         """
+        if self.is_restart:
+            params = self.load_workflow_params_and_tmpl_vars()
+        else:
+            params = []
+
         try:
             await self.initialise()
 
@@ -716,8 +719,15 @@ async def start(self):
             self.server.thread.start()
             barrier.wait()
 
+            # Get UUID now:
+            if self.is_restart:
+                self.uuid_str = dict(params)['uuid_str']
+            else:
+                self.uuid_str = str(uuid4())
+
             self._configure_contact()
-            await self.configure()
+            await self.configure(params)
+            self.task_events_mgr.uuid_str = self.uuid_str
         except (KeyboardInterrupt, asyncio.CancelledError, Exception) as exc:
             await self.handle_exception(exc)
 
@@ -1124,7 +1134,7 @@ async def command_reload_workflow(self) -> None:
             self.reload_pending = 'applying the new config'
             old_tasks = set(self.config.get_task_name_list())
             # Things that can't change on workflow reload:
-            self._load_workflow_params(
+            self._set_workflow_params(
                 self.workflow_db_mgr.pri_dao.select_workflow_params()
             )
             self.apply_new_config(config, is_reload=True)
@@ -1305,10 +1315,10 @@ def apply_new_config(self, config, is_reload=False):
             'CYLC_WORKFLOW_FINAL_CYCLE_POINT': str(self.config.final_point),
         })
 
-    def _load_workflow_params(
+    def _set_workflow_params(
         self, params: Iterable[Tuple[str, Optional[str]]]
     ) -> None:
-        """Load a row in the "workflow_params" table in a restart/reload.
+        """Set workflow params on restart/reload.
 
         This currently includes:
         * Initial/Final cycle points.

cylc/flow/task_events_mgr.py

@@ -186,7 +186,7 @@ class EventData(Enum):
 
     .. deprecated:: 8.0.0
 
-       Use 'uuid_str'.
+       Use 'uuid'.
     """
 
     CyclePoint = 'point'

cylc/flow/task_job_mgr.py

@@ -1324,7 +1324,7 @@ def get_job_conf(
             'workflow_name': workflow,
             'task_id': itask.identity,
             'try_num': itask.get_try_num(),
-            'uuid_str': self.task_remote_mgr.uuid_str,
+            'uuid_str': self.task_events_mgr.uuid_str,
             'work_d': rtconfig['work sub-directory'],
             # this field is populated retrospectively for regular job subs
             'logfiles': [],
@@ -1357,7 +1357,7 @@ def get_simulation_job_conf(self, itask, workflow):
             'workflow_name': workflow,
             'task_id': itask.identity,
             'try_num': itask.get_try_num(),
-            'uuid_str': self.task_remote_mgr.uuid_str,
+            'uuid_str': self.task_events_mgr.uuid_str,
             'work_d': 'SIMULATION',
             # this field is populated retrospectively for regular job subs
             'logfiles': [],

cylc/flow/task_remote_mgr.py

@@ -103,7 +103,6 @@ def __init__(self, workflow, proc_pool, bad_hosts, db_mgr):
         self.remote_command_map = {}
         # self.remote_init_map = {(install target): status, ...}
         self.remote_init_map = {}
-        self.uuid_str = None
         # This flag is turned on when a host init/select command completes
         self.ready = False
         self.rsync_includes = None

cylc/flow/workflow_events.py

@@ -107,7 +107,7 @@ class EventData(Enum):
 
     .. deprecated:: 8.0.0
 
-       Use "uuid_str".
+       Use "uuid".
     """
 
     # BACK COMPAT: "suite_url" deprecated

tests/functional/job-submission/01-job-nn-localhost/db.sqlite3

@@ -7,6 +7,7 @@ INSERT INTO inheritance VALUES('root','["root"]');
 INSERT INTO inheritance VALUES('foo','["foo", "root"]');
 CREATE TABLE workflow_params(key TEXT, value TEXT, PRIMARY KEY(key));
 INSERT INTO workflow_params VALUES('cylc_version', '8.0.0');
+INSERT INTO workflow_params VALUES('uuid_str', 'Something');
 CREATE TABLE workflow_template_vars(key TEXT, value TEXT, PRIMARY KEY(key));
 CREATE TABLE task_action_timers(cycle TEXT, name TEXT, ctx_key TEXT, ctx TEXT, delays TEXT, num INTEGER, delay TEXT, timeout TEXT, PRIMARY KEY(cycle, name, ctx_key));
 INSERT INTO task_action_timers VALUES('1','foo','"poll_timer"','["tuple", [[99, "running"]]]','[]',0,NULL,NULL);

tests/integration/test_examples.py

@@ -199,13 +199,13 @@ async def myflow(mod_flow, mod_scheduler, mod_one_conf):
 
 
 def test_module_scoped_fixture(myflow):
-    """Ensure the uuid is set on __init__.
+    """Ensure the host is set on __init__.
 
     The myflow fixture will be shared between all test functions within this
     Python module.
 
     """
-    assert myflow.uuid_str
+    assert myflow.host
 
 
 async def test_db_select(one, start, db_select):

tests/integration/test_scheduler.py

@@ -16,7 +16,9 @@
 
 import asyncio
 import logging
+from pathlib import Path
 import pytest
+import re
 from typing import Any, Callable
 
 from cylc.flow.exceptions import CylcError
@@ -296,6 +298,34 @@ def mock_auto_restart(*a, **k):
     assert TRACEBACK_MSG in log.text
 
 
+async def test_uuid_unchanged_on_restart(
+    one: Scheduler,
+    scheduler: Callable,
+    start: Callable,
+):
+    """Restart gets UUID from Database:
+
+    See https://github.com/cylc/cylc-flow/issues/5615
+
+    Process:
+       * Create a scheduler then shut it down.
+       * Create a new scheduler for the same workflow and check that it has
+         retrieved the UUID from the Daatabase.
+    """
+    uuid_re = re.compile('CYLC_WORKFLOW_UUID=(.*)')
+    contact_file = Path(one.workflow_run_dir) / '.service/contact'
+
+    async with start(one):
+        pass
+
+    schd = scheduler(one.workflow_name, paused_start=True)
+    async with start(schd):
+        # UUID in contact file should be the same as that set in the database
+        # and the scheduler.
+        cf_uuid = uuid_re.findall(contact_file.read_text())
+        assert cf_uuid == [schd.uuid_str]
+
+
 async def test_restart_timeout(
     flow,
     one_conf,

tests/integration/test_workflow_files.py

@@ -19,6 +19,7 @@
 from os import unlink
 from pathlib import Path
 from textwrap import dedent
+from uuid import uuid4
 
 import pytest
 
@@ -69,6 +70,7 @@ async def workflow(flow, scheduler, one_conf, run_dir):
     from collections import namedtuple
     Server = namedtuple('Server', ['port', 'pub_port'])
     schd.server = Server(1234, pub_port=2345)
+    schd.uuid_str = str(uuid4())
 
     contact_data = schd.get_contact_data()
     contact_file = Path(