Add NoNewWork node command to tell free nodes to stop asking for new work

src/agent/onefuzz-supervisor/src/coordinator.rs

@@ -25,6 +25,7 @@ pub enum NodeCommand {
     AddSshKey(SshKeyInfo),
     StopTask(StopTask),
     Stop {},
+    StopIfFree {},
 }
 
 #[derive(Debug, Deserialize, Eq, PartialEq, Serialize)]

src/agent/onefuzz-supervisor/src/scheduler.rs

@@ -71,6 +71,15 @@ impl Scheduler {
                 };
                 *self = state.into();
             }
+            NodeCommand::StopIfFree {} => {
+                if let Scheduler::Free(_) = self {
+                    let cause = DoneCause::Stopped;
+                    let state = State {
+                        ctx: Done { cause },
+                    };
+                    *self = state.into();
+                }
+            }
         }
 
         Ok(())

src/api-service/__app__/onefuzzlib/versions.py

@@ -6,6 +6,7 @@
 import os
 from typing import Dict
 
+import semver
 from memoization import cached
 from onefuzztypes.responses import Version
 
@@ -29,3 +30,8 @@ def versions() -> Dict[str, Version]:
         version=__version__,
     )
     return {"onefuzz": entry}
+
+
+def is_minimum_version(*, version: str, minimum: str) -> bool:
+    # check if version is at least (or higher) than minimum
+    return bool(semver.VersionInfo.parse(version).compare(minimum) >= 0)

src/api-service/__app__/onefuzzlib/workers/nodes.py

@@ -16,7 +16,12 @@
 )
 from onefuzztypes.models import Error
 from onefuzztypes.models import Node as BASE_NODE
-from onefuzztypes.models import NodeAssignment, NodeCommand, NodeCommandAddSshKey
+from onefuzztypes.models import (
+    NodeAssignment,
+    NodeCommand,
+    NodeCommandAddSshKey,
+    NodeCommandStopIfFree,
+)
 from onefuzztypes.models import NodeTasks as BASE_NODE_TASK
 from onefuzztypes.models import Result, StopNodeCommand, StopTaskNodeCommand
 from onefuzztypes.primitives import PoolName
@@ -26,6 +31,7 @@
 from ..azure.vmss import get_instance_id
 from ..events import send_event
 from ..orm import MappingIntStrAny, ORMMixin, QueryFilter
+from ..versions import is_minimum_version
 
 NODE_EXPIRATION_TIME: datetime.timedelta = datetime.timedelta(hours=1)
 NODE_REIMAGE_TIME: datetime.timedelta = datetime.timedelta(days=7)
@@ -338,6 +344,11 @@ def to_reimage(self, done: bool = False) -> None:
         if not self.reimage_requested and not self.delete_requested:
             logging.info("setting reimage_requested: %s", self.machine_id)
             self.reimage_requested = True
+
+        # if we're going to reimage, make sure the node doesn't pick up new work
+        # too.
+        self.send_stop_if_free()
+
         self.save()
 
     def add_ssh_public_key(self, public_key: str) -> Result[None]:
@@ -355,6 +366,10 @@ def add_ssh_public_key(self, public_key: str) -> Result[None]:
         )
         return None
 
+    def send_stop_if_free(self) -> None:
+        if is_minimum_version(version=self.version, minimum="2.16.1"):
+            self.send_message(NodeCommand(stop_if_free=NodeCommandStopIfFree()))
+
     def stop(self, done: bool = False) -> None:
         self.to_reimage(done=done)
         self.send_message(NodeCommand(stop=StopNodeCommand()))

src/api-service/__app__/onefuzzlib/workers/scalesets.py

@@ -440,10 +440,19 @@ def _resize_grow(self) -> None:
         return
 
     def _resize_shrink(self, to_remove: int) -> None:
+        logging.info(
+            SCALESET_LOG_PREFIX + "shrinking scaleset. scaleset_id:%s to_remove:%d",
+            self.scaleset_id,
+            to_remove,
+        )
         queue = ScalesetShrinkQueue(self.scaleset_id)
         for _ in range(to_remove):
             queue.add_entry()
 
+        nodes = Node.search_states(scaleset_id=self.scaleset_id)
+        for node in nodes:
+            node.send_stop_if_free()
+
     def resize(self) -> None:
         # no longer needing to resize
         if self.state != ScalesetState.resize:

src/api-service/__app__/requirements.txt

@@ -30,5 +30,6 @@ memoization~=0.3.1
 github3.py~=1.3.0
 typing-extensions~=3.7.4.3
 jsonpatch==1.28
+semver==2.13.0
 # onefuzz types version is set during build
 onefuzztypes==0.0.0

src/api-service/mypy.ini

@@ -36,4 +36,7 @@ ignore_missing_imports = True
 ignore_missing_imports = True
 
 [mypy-jsonpatch.*]
-ignore_missing_imports = True
+ignore_missing_imports = True
+
+[mypy-semver.*]
+ignore_missing_imports = True

src/api-service/tests/test_version_check.py

@@ -0,0 +1,20 @@
+#!/usr/bin/env python
+#
+# Copyright (c) Microsoft Corporation.
+# Licensed under the MIT License.
+
+import unittest
+
+from __app__.onefuzzlib.versions import is_minimum_version
+
+
+class TestMinVersion(unittest.TestCase):
+    def test_basic(self) -> None:
+        self.assertEqual(is_minimum_version(version="1.0.0", minimum="1.0.0"), True)
+        self.assertEqual(is_minimum_version(version="2.0.0", minimum="1.0.0"), True)
+        self.assertEqual(is_minimum_version(version="2.0.0", minimum="3.0.0"), False)
+        self.assertEqual(is_minimum_version(version="1.0.0", minimum="1.6.0"), False)
+
+
+if __name__ == "__main__":
+    unittest.main()

src/pytypes/onefuzztypes/models.py

@@ -557,6 +557,10 @@ class NodeHeartbeatEntry(BaseModel):
     data: List[Dict[str, HeartbeatType]]
 
 
+class NodeCommandStopIfFree(BaseModel):
+    pass
+
+
 class StopNodeCommand(BaseModel):
     pass
 
@@ -573,6 +577,7 @@ class NodeCommand(EnumModel):
     stop: Optional[StopNodeCommand]
     stop_task: Optional[StopTaskNodeCommand]
     add_ssh_key: Optional[NodeCommandAddSshKey]
+    stop_if_free: Optional[NodeCommandStopIfFree]
 
 
 class NodeCommandEnvelope(BaseModel):