From 2c54bfde335f3631f045a871c540c9d63c5bb081 Mon Sep 17 00:00:00 2001 From: Scott Gasch Date: Sun, 14 Nov 2021 22:48:04 -0800 Subject: [PATCH] Tighten up the remote executor. --- exec_utils.py | 7 +- executors.py | 253 +++++++++++++++++++++++++++++++++++++++++--------- 2 files changed, 214 insertions(+), 46 deletions(-) diff --git a/exec_utils.py b/exec_utils.py index 7e9dae5..89cfbd7 100644 --- a/exec_utils.py +++ b/exec_utils.py @@ -1,11 +1,15 @@ #!/usr/bin/env python3 import atexit +import logging import shlex import subprocess from typing import List, Optional +logger = logging.getLogger(__file__) + + def cmd_with_timeout(command: str, timeout_seconds: Optional[float]) -> int: """ Run a command but do not let it run for more than timeout seconds. @@ -72,6 +76,7 @@ def cmd_in_background( stderr=subprocess.DEVNULL) else: subproc = subprocess.Popen(args, stdin=subprocess.DEVNULL) + def kill_subproc() -> None: try: if subproc.poll() is None: @@ -79,7 +84,7 @@ def cmd_in_background( subproc.terminate() subproc.wait(timeout=10.0) except BaseException as be: - log.error(be) + logger.exception(be) atexit.register(kill_subproc) return subproc diff --git a/executors.py b/executors.py index 6723bb9..b16ad92 100644 --- a/executors.py +++ b/executors.py @@ -275,7 +275,7 @@ class RemoteExecutorStatus: ) -> None: assert self.lock.locked() self.known_workers.add(worker) - self.start_per_bundle[uuid] = time.time() + self.start_per_bundle[uuid] = None x = self.in_flight_bundles_by_worker.get(worker, set()) x.add(uuid) self.in_flight_bundles_by_worker[worker] = x @@ -292,6 +292,17 @@ class RemoteExecutorStatus: assert self.lock.locked() self.bundle_details_by_uuid[details.uuid] = details + def record_release_worker( + self, + worker: RemoteWorkerRecord, + uuid: str, + was_cancelled: bool, + ) -> None: + with self.lock: + self.record_release_worker_already_locked( + worker, uuid, was_cancelled + ) + def record_release_worker_already_locked( self, worker: RemoteWorkerRecord, @@ -309,6 +320,10 @@ class RemoteExecutorStatus: self.finished_bundle_timings_per_worker[worker] = x self.finished_bundle_timings.append(bundle_latency) + def record_processing_began(self, uuid: str): + with self.lock: + self.start_per_bundle[uuid] = time.time() + def total_in_flight(self) -> int: assert self.lock.locked() total_in_flight = 0 @@ -361,8 +376,13 @@ class RemoteExecutorStatus: None ) pid = str(details.pid) if details is not None else "TBD" - sec = ts - self.start_per_bundle[bundle_uuid] - ret += f' (pid={pid}): {bundle_uuid} for {sec:.1f}s so far ' + if self.start_per_bundle[bundle_uuid] is not None: + sec = ts - self.start_per_bundle[bundle_uuid] + ret += f' (pid={pid}): {bundle_uuid} for {sec:.1f}s so far ' + else: + ret += f' {bundle_uuid} setting up / copying data...' + sec = 0.0 + if qworker is not None: if sec > qworker[1]: ret += f'{bg("red")}>💻p95{reset()} ' @@ -491,6 +511,7 @@ class RemoteExecutor(BaseExecutor): raise Exception(msg) self.policy.register_worker_pool(self.workers) self.cv = threading.Condition() + logger.debug(f'Creating {self.worker_count} local threads, one per remote worker.') self._helper_executor = fut.ThreadPoolExecutor( thread_name_prefix="remote_executor_helper", max_workers=self.worker_count, @@ -536,7 +557,8 @@ class RemoteExecutor(BaseExecutor): self.status.periodic_dump(self.total_bundles_submitted) # Look for bundles to reschedule - if len(self.status.finished_bundle_timings) > 7: + num_done = len(self.status.finished_bundle_timings) + if num_done > 7 or (num_done > 5 and self.is_worker_available()): for worker, bundle_uuids in self.status.in_flight_bundles_by_worker.items(): for uuid in bundle_uuids: bundle = self.status.bundle_details_by_uuid.get(uuid, None) @@ -576,25 +598,28 @@ class RemoteExecutor(BaseExecutor): return True return False - def launch(self, bundle: BundleDetails) -> Any: + def launch(self, bundle: BundleDetails, override_avoid_machine=None) -> Any: """Find a worker for bundle or block until one is available.""" self.adjust_task_count(+1) uuid = bundle.uuid hostname = bundle.hostname - avoid_machine = None + avoid_machine = override_avoid_machine + is_original = bundle.src_bundle is None # Try not to schedule a backup on the same host as the original. - if bundle.src_bundle is not None: + if avoid_machine is None and bundle.src_bundle is not None: avoid_machine = bundle.src_bundle.machine worker = None while worker is None: worker = self.find_available_worker_or_block(avoid_machine) + + # Ok, found a worker. bundle.worker = worker machine = bundle.machine = worker.machine username = bundle.username = worker.username fname = bundle.fname self.status.record_acquire_worker(worker, uuid) - logger.debug(f'Running bundle {uuid} on {worker}...') + logger.debug(f'{uuid}/{fname}: Running bundle on {worker}...') # Before we do any work, make sure the bundle is still viable. if self.check_if_cancelled(bundle): @@ -602,54 +627,151 @@ class RemoteExecutor(BaseExecutor): return self.post_launch_work(bundle) except Exception as e: logger.exception(e) - logger.info(f"{uuid}/{fname}: bundle seems to have failed?!") - if bundle.failure_count < config.config['executors_max_bundle_failures']: - return self.launch(bundle) + logger.error( + f'{uuid}/{fname}: bundle says it\'s cancelled upfront but no results?!' + ) + assert bundle.worker is not None + self.status.record_release_worker( + bundle.worker, + bundle.uuid, + True, + ) + self.release_worker(bundle.worker) + self.adjust_task_count(-1) + if is_original: + # Weird. We are the original owner of this + # bundle. For it to have been cancelled, a backup + # must have already started and completed before + # we even for started. Moreover, the backup says + # it is done but we can't find the results it + # should have copied over. Reschedule the whole + # thing. + return self.emergency_retry_nasty_bundle(bundle) else: - logger.info(f"{uuid}/{fname}: bundle is poison, giving up on it.") + # Expected(?). We're a backup and our bundle is + # cancelled before we even got started. Something + # went bad in post_launch_work (I acutually don't + # see what?) but probably not worth worrying + # about. return None - # Send input to machine if it's not local. + # Send input code / data to worker machine if it's not local. if hostname not in machine: - cmd = f'{RSYNC} {bundle.code_file} {username}@{machine}:{bundle.code_file}' - logger.info(f"{uuid}/{fname}: Copying work to {worker} via {cmd}") - run_silently(cmd) + try: + cmd = f'{RSYNC} {bundle.code_file} {username}@{machine}:{bundle.code_file}' + start_ts = time.time() + logger.info(f"{uuid}/{fname}: Copying work to {worker} via {cmd}.") + run_silently(cmd) + xfer_latency = time.time() - start_ts + logger.info(f"{uuid}/{fname}: Copying done in {xfer_latency}s.") + except Exception as e: + logger.exception(e) + logger.error( + f'{uuid}/{fname}: failed to send instructions to worker machine?!?' + ) + assert bundle.worker is not None + self.status.record_release_worker( + bundle.worker, + bundle.uuid, + True, + ) + self.release_worker(bundle.worker) + self.adjust_task_count(-1) + if is_original: + # Weird. We tried to copy the code to the worker and it failed... + # And we're the original bundle. We have to retry. + return self.emergency_retry_nasty_bundle(bundle) + else: + # This is actually expected; we're a backup. + # There's a race condition where someone else + # already finished the work and removed the source + # code file before we could copy it. No biggie. + return None - # Do it. + # Kick off the work. Note that if this fails we let + # wait_for_process deal with it. + self.status.record_processing_began(uuid) cmd = (f'{SSH} {bundle.username}@{bundle.machine} ' f'"source py39-venv/bin/activate &&' f' /home/scott/lib/python_modules/remote_worker.py' f' --code_file {bundle.code_file} --result_file {bundle.result_file}"') + logger.debug(f'{uuid}/{fname}: Executing {cmd} in the background to kick off work...') p = cmd_in_background(cmd, silent=True) bundle.pid = pid = p.pid - logger.info(f"{uuid}/{fname}: Start training on {worker} via {cmd} (background pid {pid})") + logger.debug(f'{uuid}/{fname}: Local ssh process pid={pid}; remote worker is {machine}.') + return self.wait_for_process(p, bundle, 0) + + def wait_for_process(self, p: subprocess.Popen, bundle: BundleDetails, depth: int) -> Any: + uuid = bundle.uuid + machine = bundle.machine + fname = bundle.fname + pid = p.pid + if depth > 3: + logger.error( + f"I've gotten repeated errors waiting on this bundle; giving up on pid={pid}." + ) + p.terminate() + self.status.record_release_worker( + bundle.worker, + bundle.uuid, + True, + ) + self.release_worker(bundle.worker) + self.adjust_task_count(-1) + return self.emergency_retry_nasty_bundle(bundle) + # Spin until either the ssh job we scheduled finishes the + # bundle or some backup worker signals that they finished it + # before we could. while True: try: p.wait(timeout=0.25) except subprocess.TimeoutExpired: self.heartbeat() - - # Both source and backup bundles can be cancelled by - # the other depending on which finishes first. if self.check_if_cancelled(bundle): - p.terminate() + logger.info( + f'{uuid}/{fname}: another worker finished bundle, checking it out...' + ) break else: - logger.debug( - f"{uuid}/{fname}: pid {pid} has finished its work normally." + logger.info( + f"{uuid}/{fname}: pid {pid} ({machine}) our ssh finished, checking it out..." ) + p = None break + # If we get here we believe the bundle is done; either the ssh + # subprocess finished (hopefully successfully) or we noticed + # that some other worker seems to have completed the bundle + # and we're bailing out. try: - return self.post_launch_work(bundle) + ret = self.post_launch_work(bundle) + if ret is not None and p is not None: + p.terminate() + return ret + + # Something went wrong; e.g. we could not copy the results + # back, cleanup after ourselves on the remote machine, or + # unpickle the results we got from the remove machine. If we + # still have an active ssh subprocess, keep waiting on it. + # Otherwise, time for an emergency reschedule. except Exception as e: logger.exception(e) - logger.info(f"{uuid}: Bundle seems to have failed?!") - if bundle.failure_count < config.config['executors_max_bundle_failures']: - return self.launch(bundle) - logger.info(f"{uuid}: Bundle is poison, giving up on it.") - return None + logger.error(f'{uuid}/{fname}: Something unexpected just happened...') + if p is not None: + logger.warning( + f"{uuid}/{fname}: Failed to wrap up \"done\" bundle, re-waiting on active ssh." + ) + return self.wait_for_process(p, bundle, depth + 1) + else: + self.status.record_release_worker( + bundle.worker, + bundle.uuid, + True, + ) + self.release_worker(bundle.worker) + self.adjust_task_count(-1) + return self.emergency_retry_nasty_bundle(bundle) def post_launch_work(self, bundle: BundleDetails) -> Any: with self.status.lock: @@ -673,20 +795,14 @@ class RemoteExecutor(BaseExecutor): logger.info( f"{uuid}/{fname}: Fetching results from {username}@{machine} via {cmd}" ) - try: - run_silently(cmd) - except subprocess.CalledProcessError: - logger.critical(f'Failed to copy {username}@{machine}:{result_file}!') + + # If either of these throw they are handled in + # wait_for_process. + run_silently(cmd) run_silently(f'{SSH} {username}@{machine}' f' "/bin/rm -f {code_file} {result_file}"') dur = bundle.end_ts - bundle.start_ts self.histogram.add_item(dur) - assert bundle.worker is not None - self.status.record_release_worker_already_locked( - bundle.worker, - bundle.uuid, - was_cancelled - ) # Only the original worker should unpickle the file contents # though since it's the only one whose result matters. The @@ -701,11 +817,22 @@ class RemoteExecutor(BaseExecutor): serialized = rb.read() result = cloudpickle.loads(serialized) except Exception as e: - msg = f'Failed to load {result_file}' + msg = f'Failed to load {result_file}, this is bad news.' logger.critical(msg) - bundle.failure_count += 1 + self.status.record_release_worker( + bundle.worker, + bundle.uuid, + True, + ) self.release_worker(bundle.worker) + + # Re-raise the exception; the code in wait_for_process may + # decide to emergency_retry_nasty_bundle here. raise Exception(e) + + logger.debug( + f'Removing local (master) {code_file} and {result_file}.' + ) os.remove(f'{result_file}') os.remove(f'{code_file}') @@ -720,7 +847,8 @@ class RemoteExecutor(BaseExecutor): ) backup.is_cancelled.set() - # This is a backup job. + # This is a backup job and, by now, we have already fetched + # the bundle results. else: # Backup results don't matter, they just need to leave the # result file in the right place for their originals to @@ -730,11 +858,16 @@ class RemoteExecutor(BaseExecutor): # Tell the original to stop if we finished first. if not was_cancelled: logger.debug( - f'{uuid}/{fname}: Notifying original {bundle.src_bundle.uuid} that it\'s cancelled' + f'{uuid}/{fname}: Notifying original {bundle.src_bundle.uuid} we beat them to it.' ) bundle.src_bundle.is_cancelled.set() assert bundle.worker is not None + self.status.record_release_worker( + bundle.worker, + bundle.uuid, + was_cancelled, + ) self.release_worker(bundle.worker) self.adjust_task_count(-1) return result @@ -818,6 +951,36 @@ class RemoteExecutor(BaseExecutor): # they will move the result_file to this machine and let # the original pick them up and unpickle them. + def emergency_retry_nasty_bundle(self, bundle: BundleDetails) -> fut.Future: + uuid = bundle.uuid + is_original = bundle.src_bundle is None + bundle.worker = None + avoid_last_machine = bundle.machine + bundle.machine = None + bundle.username = None + bundle.failure_count += 1 + if is_original: + retry_limit = 3 + else: + retry_limit = 2 + + if bundle.failure_count > retry_limit: + logger.error( + f'{uuid}: Tried this bundle too many times already ({retry_limit}x); giving up.' + ) + if is_original: + logger.critical( + f'{uuid}: This is the original of the bundle; results will be incomplete.' + ) + else: + logger.error(f'{uuid}: At least it\'s only a backup; better luck with the others.') + return None + else: + logger.warning( + f'>>> Emergency rescheduling {uuid} because of unexected errors (wtf?!) <<<' + ) + return self.launch(bundle, avoid_last_machine) + @overrides def submit(self, function: Callable, @@ -862,8 +1025,8 @@ class DefaultExecutors(object): return self.process_executor def remote_pool(self) -> RemoteExecutor: - logger.info('Looking for some helper machines...') if self.remote_executor is None: + logger.info('Looking for some helper machines...') pool: List[RemoteWorkerRecord] = [] if self.ping('cheetah.house'): logger.info('Found cheetah.house') -- 2.47.1