pool: update the runahead limit after task removal

changes.d/4983.fix.md

@@ -0,0 +1 @@
+Ensure the runahead limit is recomputed when legacy "suicide-triggers" are used to prevent erroneous stall in niche cases.

cylc/flow/task_pool.py

@@ -877,6 +877,10 @@ def remove(self, itask, reason=None):
 
  del itask
 
+ # removing this task could nudge the runahead limit forward
+ if self.compute_runahead():
+ self.release_runahead_tasks()
+
  def get_tasks(self) -> List[TaskProxy]:
  """Return a list of task proxies in the task pool."""
  # Cached list only for use internally in this method.

tests/integration/test_compat_mode.py

@@ -0,0 +1,125 @@
+# THIS FILE IS PART OF THE CYLC WORKFLOW ENGINE.
+# Copyright (C) NIWA & British Crown (Met Office) & Contributors.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+"""Tests for Cylc 7 compatibility mode."""
+
+from typing import TYPE_CHECKING
+
+from cylc.flow.cycling.integer import IntegerPoint
+from cylc.flow.data_store_mgr import TASK_PROXIES
+
+if TYPE_CHECKING:
+ from cylc.flow.scheduler import Scheduler
+
+
+async def test_blocked_tasks_in_n0(flow, scheduler, run, complete):
+ """Ensure that tasks with no satisfied dependencies remain in the pool.
+
+ In this example, the "recover" task is not satisfiable because its upstream
+ dependency "foo:failed" will never be satisfied. The unsatisfiable
+ "recover" task should remain in n=0 until removed/completed.
+
+ See https:/cylc/cylc-flow/issues/4983
+ """
+ id_ = flow(
+ {
+ 'scheduling': {
+ 'initial cycle point': '1',
+ 'cycling mode': 'integer',
+ 'runahead limit': 'P2',
+ 'dependencies': {
+ 'P1': {
+ 'graph': '''
+ foo:fail => recover
+ foo | recover => bar
+ ''',
+ },
+ },
+ },
+ },
+ filename='suite.rc',
+ )
+ schd: 'Scheduler' = scheduler(id_, paused_start=False, debug=True)
+ async with run(schd):
+ # the workflow should run for three cycles, then runahead stall
+ await complete(schd, *(f'{cycle}/bar' for cycle in range(1, 4)))
+ assert schd.is_stalled
+
+ # the "blocked" recover tasks should remain in the pool
+ assert {t.identity for t in schd.pool.get_tasks()} == {
+ '1/recover',
+ '2/recover',
+ '3/recover',
+ '4/foo',
+ }
+
+ # the "blocked" tasks should remain visible in the data store
+ assert {
+ (x.cycle_point, x.graph_depth, x.name)
+ for x in schd.data_store_mgr.data[schd.tokens.id][
+ TASK_PROXIES
+ ].values()
+ } == {
+ ('1', 1, 'foo'),
+ ('1', 0, 'recover'),
+ ('1', 0, 'bar'), # NOTE: this should be n=2 not n=0
+ ('2', 1, 'foo'),
+ ('2', 0, 'recover'),
+ ('2', 0, 'bar'), # NOTE: this should be n=2 not n=0
+ ('3', 1, 'foo'),
+ ('3', 0, 'recover'),
+ ('3', 0, 'bar'), # NOTE: this should be n=2 not n=0
+ ('4', 0, 'foo'),
+ ('4', 1, 'recover'),
+ ('4', 1, 'bar'),
+ }
+
+ # remove the unsatisfiable tasks
+ # (i.e. manually implement a suicide trigger)
+ for cycle in range(1, 4):
+ itask = schd.pool.get_task(IntegerPoint(str(cycle)), 'recover')
+ schd.pool.remove(itask, 'suicide-trigger')
+ assert {t.identity for t in schd.pool.get_tasks()} == {
+ '4/foo',
+ '5/foo',
+ '6/foo',
+ '7/foo',
+ }
+
+ # the workflow continue into the next three cycles, then stall again
+ # (i.e. the runahead limit should move forward after the removes)
+ await complete(schd, *(f'{cycle}/bar' for cycle in range(4, 7)))
+ assert schd.is_stalled
+
+ assert {
+ (x.cycle_point, x.graph_depth, x.name)
+ for x in schd.data_store_mgr.data[schd.tokens.id][
+ TASK_PROXIES
+ ].values()
+ } == {
+ ('4', 1, 'foo'),
+ ('4', 0, 'recover'),
+ ('4', 0, 'bar'), # NOTE: this should be n=2 not n=0
+ ('5', 1, 'foo'),
+ ('5', 0, 'recover'),
+ ('5', 0, 'bar'), # NOTE: this should be n=2 not n=0
+ ('6', 1, 'foo'),
+ ('6', 0, 'recover'),
+ ('6', 0, 'bar'), # NOTE: this should be n=2 not n=0
+ ('7', 0, 'foo'),
+ ('7', 1, 'recover'),
+ ('7', 1, 'bar'),
+ }

tests/integration/utils/flow_tools.py

@@ -39,13 +39,13 @@
 from .flow_writer import flow_config_str
 
 
-def _make_src_flow(src_path, conf):
+def _make_src_flow(src_path, conf, filename=WorkflowFiles.FLOW_FILE):
  """Construct a workflow on the filesystem"""
  flow_src_dir = (src_path / str(uuid1()))
  flow_src_dir.mkdir(parents=True, exist_ok=True)
  if isinstance(conf, dict):
  conf = flow_config_str(conf)
- with open((flow_src_dir / WorkflowFiles.FLOW_FILE), 'w+') as flow_file:
+ with open((flow_src_dir / filename), 'w+') as flow_file:
  flow_file.write(conf)
  return flow_src_dir
 
@@ -57,6 +57,7 @@ def _make_flow(
  name: Optional[str] = None,
  id_: Optional[str] = None,
  defaults: Optional[bool] = True,
+ filename: str = WorkflowFiles.FLOW_FILE,
 ) -> str:
  """Construct a workflow on the filesystem.
 
@@ -86,7 +87,7 @@ def _make_flow(
  conf.setdefault('scheduler', {}).setdefault(
  'allow implicit tasks', 'True')
 
- with open((flow_run_dir / WorkflowFiles.FLOW_FILE), 'w+') as flow_file:
+ with open((flow_run_dir / filename), 'w+') as flow_file:
  flow_file.write(flow_config_str(conf))
  return id_