def rendezvous_barrier(self):
"""
Main entry point for next rendezvous.
This method is blocking until rendezvous succeeds or a timeout occurs.
Returns:
``(rdzv_version, rank, world_size)``
Raises:
RendezvousTimeoutError - timeout waiting for rendezvous
RendezvousClosedError - rendezvous is or was closed while waiting
RendezvousError - other persistent errors that
render the rendezvous non-retryable
"""
self._rendezvous_deadline = time.time() + self._timeout
while True:
if time.time() > self._rendezvous_deadline:
raise RendezvousTimeoutError()
log.info("Attempting to join next rendezvous")
try:
# Dis-own our lease in the previous rendezvous, if exists
if self._lease_this_rank_stop is not None:
self._lease_this_rank_stop.set()
return self.init_phase()
except EtcdRendezvousRetryImmediately:
# The type of failure suggests we can retry without delay
pass
except EtcdRendezvousRetryableFailure:
# In case of retryable failure, wait a small delay
# to avoid spamming etcd
time.sleep(1)
except RendezvousTimeoutError:
log.info("Rendezvous timeout occured in EtcdRendezvousHandler")
raise
except RendezvousClosedError:
log.info(
f"Rendezvous for run_id={self._run_id} was observed to be closed"
)
raise
except RendezvousError:
raise
except Exception as e:
# In case of a general exception, wait a small delay
# to avoid spamming etcd
# FIXME: there are a few things that fall under this like
# etcd.EtcdKeyNotFound, etc, which could be handled more explicitly.
log.info("Rendezvous attempt failed, will retry. Reason: " +
str(e))
time.sleep(1)
def try_wait_for_state_change(self, etcd_index, timeout=None):
# Don't sleep past the overall deadline (at least more than by 1s)
overall_timeout = max(self._rendezvous_deadline - time.time(),
0.0) + 1.0
timeout = overall_timeout if timeout is None else min(
timeout, overall_timeout)
try:
self.client.watch(self.get_path("/rdzv/active_version"),
index=etcd_index,
timeout=timeout)
except (etcd.EtcdEventIndexCleared, etcd.EtcdWatchTimedOut):
pass
if time.time() > self._rendezvous_deadline:
raise RendezvousTimeoutError()
# Unfortunately, we have to do another fetch in order to get last etcd_index.
return self.get_rdzv_state()
def wait_for_rendezvous_to_free(self, expected_version):
"""
When there's an existing valid rendezvous in state 'final', we have to
wait until the next opportunity to join.
Such opportunity may come from:
1. rendezvous state changed by someone else, in which case we unblock and retry.
2. rendezvous becomes invalid because at least one member failed to renew their
leased keep_alive node. We detect this, and destroy the rendezvous.
"""
active_version, state = self.get_rdzv_state()
while True:
if state["status"] != "final" or state[
"version"] != expected_version:
return
# Check if current rendezvous state is valid, in the sense that all
# its members are alive (renewing their lease).
# If not, try destroy this rendezvous, so a new one can be created.
alive_members = self.client.get(
self.get_path(
"/rdzv/v_{version}".format(version=expected_version)))
keep_alive_keys = [ch.key for ch in alive_members.children]
for key in state["keep_alives"]:
if key not in keep_alive_keys:
# This participant didn't renew their lease. We'll declare this
# rendezvous version as dead (but only if it hadn't changed)
log.info("Keep-alive key {} is not renewed.".format(key))
log.info("Rendevous version {} is incomplete. ".format(
expected_version))
log.info("Attempting to destroy it.")
# Compare-and-delete operation. Throws if compare failed,
# which means rendezvous was already destroyed/re-created/closed,
# and we can try to re-enter the barrier.
self.client.delete(
key=self.get_path("/rdzv/active_version"),
prevValue=active_version.value,
)
log.info(
"Destroyed rendezvous version {} successfully.".format(
expected_version))
# We can return (and retry) immediately
return
# Existing rendezvous seems valid, no reason to destroy it.
# We just have to wait until something changes and re-check.
try:
overall_timeout = (
max(self._rendezvous_deadline - time.time(), 0.0) + 1.0)
self.client.watch(
key=self.get_path("/rdzv"),
index=active_version.etcd_index + 1,
recursive=True,
timeout=overall_timeout,
)
except (etcd.EtcdEventIndexCleared, etcd.EtcdWatchTimedOut):
pass
if time.time() > self._rendezvous_deadline:
raise RendezvousTimeoutError()
active_version, state = self.get_rdzv_state()