Every three minutes validate a random run from the cache.

The reason for this PR is that before introducing more dynamic
updates we would like to verify that the dynamic updates of
run["workers"] and run["cores"] introduced in
official-stockfish#2010
are bug free.

In order to facilitate the use of periodic timers in Fishtest
we have introduced a new scheduler in utils.py which may be
interesting in its own right.

Currently the timers defined are the cache flush timer and the
timer introduced in this PR.

server/fishtest/__init__.py

@@ -100,7 +100,7 @@ def init_rundb(event):
         if rundb.is_primary_instance():
             signal.signal(signal.SIGINT, rundb.exit_run)
             signal.signal(signal.SIGTERM, rundb.exit_run)
-            rundb.start_timer()
+            rundb.schedule_tasks()
             rundb.update_workers_cores()
 
     config.add_subscriber(add_rundb, NewRequest)

server/fishtest/rundb.py

@@ -17,11 +17,18 @@
 from bson.errors import InvalidId
 from bson.objectid import ObjectId
 from fishtest.actiondb import ActionDb
-from fishtest.schemas import RUN_VERSION, nn_schema, pgns_schema, runs_schema
+from fishtest.schemas import (
+    RUN_VERSION,
+    nn_schema,
+    pgns_schema,
+    runs_schema,
+    valid_aggregated_data,
+)
 from fishtest.stats.stat_util import SPRT_elo
 from fishtest.userdb import UserDb
 from fishtest.util import (
     GeneratorAsFileReader,
+    Scheduler,
     crash_or_time,
     estimate_game_duration,
     format_bounds,
@@ -73,8 +80,43 @@ def __init__(self, db_name="fishtest_new", port=-1, is_primary_instance=True):
         self.__is_primary_instance = is_primary_instance
 
         self.request_task_lock = threading.Lock()
-        self.timer = None
-        self.timer_active = True
+        self.scheduler = None
+
+    def schedule_tasks(self):
+        if self.scheduler is None:
+            self.scheduler = Scheduler(jitter=0.05)
+        self.scheduler.add_task(1.0, self.flush_buffers)
+        self.scheduler.add_task(180.0, self.validate_random_run)
+
+    def validate_random_run(self):
+        run_list = list(self.run_cache.values())
+        if len(run_list) == 0:
+            print(
+                "Validate_random_run: cache empty. No runs to validate...", flush=True
+            )
+            return
+        run = random.choice(list(run_list))["run"]
+        run_id = str(run["_id"])
+        try:
+            # Make sure that the run object does not change while we are
+            # validating it
+            with self.active_run_lock(run_id):
+                # We verify only the aggregated data since the other
+                # data is not synchronized and may be in a transient
+                # inconsistent state
+                validate(valid_aggregated_data, run, "run")
+                print(
+                    f"Validate_random_run: validated aggregated data in cache run {run_id}...",
+                    flush=True,
+                )
+        except ValidationError as e:
+            message = f"The run object {run_id} does not validate: {str(e)}"
+            print(message, flush=True)
+            if "version" in run and run["version"] >= RUN_VERSION:
+                self.actiondb.log_message(
+                    username="fishtest.system",
+                    message=message,
+                )
 
     def set_inactive_run(self, run):
         run_id = run["_id"]
@@ -348,7 +390,8 @@ def get_nns(self, user="", network_name="", master_only=False, limit=0, skip=0):
 
     # handle termination
     def exit_run(self, signum, frame):
-        self.stop_timer()
+        if self.scheduler is not None:
+            self.scheduler.stop()
         self.flush_all()
         if self.port >= 0:
             self.actiondb.system_event(message=f"stop fishtest@{self.port}")
@@ -378,17 +421,6 @@ def get_run(self, r_id):
         else:
             return self.runs.find_one({"_id": r_id_obj})
 
-    def stop_timer(self):
-        if self.timer is not None:
-            self.timer.cancel()
-        self.timer = None
-        self.timer_active = False
-
-    def start_timer(self):
-        if self.timer_active:
-            self.timer = threading.Timer(1.0, self.flush_buffers)
-            self.timer.start()
-
     def buffer(self, run, flush):
         if not self.is_primary_instance():
             print(
@@ -438,8 +470,6 @@ def flush_all(self):
         print("done", flush=True)
 
     def flush_buffers(self):
-        if self.timer is None:
-            return
         try:
             self.run_cache_lock.acquire()
             now = time.time()
@@ -476,9 +506,7 @@ def flush_buffers(self):
         except:
             print("Flush exception", flush=True)
         finally:
-            # Restart timer:
             self.run_cache_lock.release()
-            self.start_timer()
 
     def scavenge(self, run):
         if datetime.now(timezone.utc) < boot_time + timedelta(seconds=300):

server/fishtest/schemas.py

@@ -486,9 +486,43 @@ def final_results_must_match(run):
         raise Exception(
             f"The final results {run['results']} do not match the computed results {rr}"
         )
-    else:
-        return True
 
+    return True
+
+
+def cores_must_match(run):
+    cores = 0
+    for t in run["tasks"]:
+        if t["active"]:
+            cores += t["worker_info"]["concurrency"]
+    if cores != run["cores"]:
+        raise Exception(
+            f"Cores mismatch. Cores from tasks: {cores}. Cores from "
+            f"run: {run['cores']}"
+        )
+
+    return True
+
+
+def workers_must_match(run):
+    workers = 0
+    for t in run["tasks"]:
+        if t["active"]:
+            workers += 1
+    if workers != run["workers"]:
+        raise Exception(
+            f"Workers mismatch. Workers from tasks: {workers}. Workers from "
+            f"run: {run['workers']}"
+        )
+
+    return True
+
+
+valid_aggregated_data = intersect(
+    final_results_must_match,
+    cores_must_match,
+    workers_must_match,
+)
 
 # The following schema only matches new runs. The old runs
 # are not compatible with it. For documentation purposes
@@ -655,5 +689,5 @@ def final_results_must_match(run):
     lax(ifthen({"deleted": True}, {"finished": True})),
     lax(ifthen({"finished": True}, {"workers": 0, "cores": 0})),
     lax(ifthen({"finished": True}, {"tasks": [{"active": False}, ...]})),
-    final_results_must_match,
+    valid_aggregated_data,
 )

server/fishtest/util.py

@@ -3,9 +3,11 @@
 import math
 import re
 import smtplib
+import threading
 from datetime import datetime, timedelta, timezone
 from email.mime.text import MIMEText
 from functools import cache
+from random import uniform
 
 import fishtest.stats.stat_util
 import numpy
@@ -545,3 +547,145 @@ def strip_run(run):
         stripped[key] = str(run[key])
 
     return stripped
+
+
+"""
+The following scheduling code should be thread safe.
+
+- First and foremost, all tasks are executed in a single main thread.
+So they are atomic. In particular, between its scheduling and descheduling,
+a task will be a executed exactly once at each scheduling point.
+
+- The main thread maintains a list of scheduled tasks. To safely manipulate
+this list outside the main thread we rely on the atomicity of in-place
+list operations in Python.
+
+- To signal the main thread that the task list has changed, which should
+be acted upon as soon as possible as it might affect the next task to
+be executed, we use a threading.Event.
+
+Example
+
+s=Scheduler()
+s.add_task(3, task1)
+s.add_task(2, task2)
+
+When the second task is scheduled, the scheduler will interrupt the
+3s wait for the first task and replace it by a 2s wait for the second task.
+"""
+
+
+class Task:
+    def __init__(
+        self,
+        period,
+        worker,
+        initial_delay=None,
+        one_shot=False,
+        jitter=0.0,
+        args=(),
+        kwargs={},
+    ):
+        self.period = timedelta(seconds=period)
+        self.worker = worker
+        if initial_delay is None:
+            initial_delay = self.period
+        else:
+            initial_delay = timedelta(seconds=initial_delay)
+        self.__rel_jitter = jitter * self.period
+        self.__next_schedule = (
+            datetime.now(timezone.utc)
+            + initial_delay
+            + uniform(-self.__rel_jitter, self.__rel_jitter)
+        )
+        self.one_shot = one_shot
+        self.__expired = False
+        self.args = args
+        self.kwargs = kwargs
+
+    def do_work(self):
+        if self.__expired:
+            return
+        try:
+            self.worker(*self.args, *self.kwargs)
+        except Exception as e:
+            print(f"Exception while executing task: {str(e)}", flush=True)
+        if not self.one_shot:
+            self.__next_schedule += self.period + uniform(
+                -self.__rel_jitter, self.__rel_jitter
+            )
+        else:
+            self.__expired = True
+
+    def next_schedule(self):
+        return self.__next_schedule
+
+    def expired(self):
+        return self.__expired
+
+
+class Scheduler:
+    def __init__(self, jitter=0.0):
+        self.__tasks = []
+        self.__timer_stopped = False
+        self.__event = threading.Event()
+        self.jitter = jitter
+        # dummy task to avoid special casing an empty task list
+        self.add_task(3600.0, lambda: None, jitter=0.1)
+        self.__worker_thread = threading.Thread(target=self.__next_schedule)
+        self.__worker_thread.start()
+
+    def add_task(
+        self,
+        period,
+        worker,
+        initial_delay=None,
+        one_shot=False,
+        jitter=None,
+        args=(),
+        kwargs={},
+    ):
+        if jitter is None:
+            jitter = self.jitter
+        task = Task(
+            period,
+            worker,
+            initial_delay=initial_delay,
+            one_shot=one_shot,
+            jitter=jitter,
+            args=args,
+            kwargs=kwargs,
+        )
+        self.__tasks.append(task)
+        self.__event.set()
+        return task
+
+    def del_task(self, task):
+        self.__del_task(task)
+        self.__event.set()
+
+    def stop(self):
+        self.__timer_stopped = True
+        self.__event.set()
+
+    def __del_task(self, task):
+        try:
+            self.__tasks.remove(task)
+        except Exception:
+            pass
+
+    def __next_schedule(self):
+        while not self.__timer_stopped:
+            next_schedule = None
+            for task in copy.copy(self.__tasks):
+                if task.expired():
+                    self.__del_task(task)
+                else:
+                    if next_schedule is None or task.next_schedule() < next_schedule:
+                        next_task = task
+                        next_schedule = task.next_schedule()
+            delay = (next_schedule - datetime.now(timezone.utc)).total_seconds()
+            self.__event.wait(delay)
+            if not self.__event.is_set():
+                next_task.do_work()
+            self.__event.clear()