Ensure that UUID is retrieved from database on workflow restart.

cylc/flow/scheduler.py

@@ -281,7 +281,6 @@ def __init__(self, reg: 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)
 
@@ -306,6 +305,9 @@ def __init__(self, reg: 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()
+        if not self.is_restart:
+            self.uuid_str = str(uuid4())
+
         # Map used to track incomplete remote inits for restart
         # {install_target: platform}
         self.incomplete_ri_map: Dict[str, Dict] = {}
@@ -393,7 +395,6 @@ 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,
@@ -403,7 +404,6 @@ 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)
 
@@ -701,8 +701,10 @@ async def start(self):
             self.server.thread.start()
             barrier.wait()
 
-            self._configure_contact()
             await self.configure()
+            self.task_events_mgr.uuid_str = self.uuid_str
+            self.task_job_mgr.task_remote_mgr.uuid_str = self.uuid_str
+            self._configure_contact()
         except (KeyboardInterrupt, asyncio.CancelledError, Exception) as exc:
             await self.handle_exception(exc)
 

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_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
@@ -292,3 +294,31 @@ def mock_auto_restart(*a, **k):
 
     assert log_filter(log, level=logging.ERROR, contains=err_msg)
     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())[0]
+        assert schd.uuid_str == cf_uuid