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Defer version check until after bootstrap succeeds #1426

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Defer version check until after bootstrap succeeds #1426

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27 changes: 15 additions & 12 deletions kafka/client_async.py
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Original file line number Diff line number Diff line change
Expand Up @@ -196,6 +196,9 @@ def __init__(self, **configs):
assert self.config['api_version'] in self.API_VERSIONS, (
'api_version [{0}] must be one of: {1}'.format(
self.config['api_version'], str(self.API_VERSIONS)))
else:
# This should get updated after a successful bootstrap
self.config['api_version'] = (0, 0)

self.cluster = ClusterMetadata(**self.config)
self._topics = set() # empty set will fetch all topic metadata
Expand Down Expand Up @@ -228,11 +231,6 @@ def __init__(self, **configs):

self._bootstrap(collect_hosts(self.config['bootstrap_servers']))

# Check Broker Version if not set explicitly
if self.config['api_version'] is None:
check_timeout = self.config['api_version_auto_timeout_ms'] / 1000
self.config['api_version'] = self.check_version(timeout=check_timeout)

def _bootstrap(self, hosts):
log.info('Bootstrapping cluster metadata from %s', hosts)
# Exponential backoff if bootstrap fails
Expand All @@ -245,7 +243,7 @@ def _bootstrap(self, hosts):
time.sleep(next_at - now)
self._last_bootstrap = time.time()

if self.config['api_version'] is None or self.config['api_version'] < (0, 10):
if self.config['api_version'] < (0, 10):
metadata_request = MetadataRequest[0]([])
else:
metadata_request = MetadataRequest[1](None)
Expand Down Expand Up @@ -283,7 +281,13 @@ def _bootstrap(self, hosts):
else:
bootstrap.close()
self._bootstrap_fails = 0

# Check Broker Version if not set explicitly
if self.config['api_version'] == (0, 0):
check_timeout = self.config['api_version_auto_timeout_ms'] / 1000
self.config['api_version'] = self.check_version(timeout=check_timeout)
break

# No bootstrap found...
else:
log.error('Unable to bootstrap from %s', hosts)
Expand Down Expand Up @@ -821,10 +825,10 @@ def check_version(self, node_id=None, timeout=2, strict=False):
This is only possible if node_id is None.

Returns: version tuple, i.e. (0, 10), (0, 9), (0, 8, 2), ...
(0, 0) returned if the version cannot be determined,
typically due to networking.

Raises:
NodeNotReadyError (if node_id is provided)
NoBrokersAvailable (if node_id is None)
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@jeffwidman jeffwidman Mar 16, 2018 •
edited
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So what happens if bootstrapping eventually fails? Will these still get raised somewhere else in the stack?

I know there's code in the wild that is expecting these exceptions, as I used it myself when I updated the Datadog kafka consumer lag check to use the async KafkaClient instead of the old SimpleClient before we had the new KafkaAdminClient.

To clarify, I'm not against this change, I just want to understand the new behavior.

UnrecognizedBrokerVersion: please file bug if seen!
AssertionError (if strict=True): please file bug if seen!
"""
Expand All @@ -835,7 +839,7 @@ def check_version(self, node_id=None, timeout=2, strict=False):
# which can block for an increasing backoff period
try_node = node_id or self.least_loaded_node()
if try_node is None:
raise Errors.NoBrokersAvailable()
return (0, 0)
self._maybe_connect(try_node)
conn = self._conns[try_node]

Expand All @@ -847,15 +851,14 @@ def check_version(self, node_id=None, timeout=2, strict=False):
version = conn.check_version(timeout=remaining, strict=strict)
return version
except Errors.NodeNotReadyError:
# Only raise to user if this is a node-specific request
if node_id is not None:
raise
return (0, 0)
finally:
self._refresh_on_disconnects = True

# Timeout
else:
raise Errors.NoBrokersAvailable()
return (0, 0)

def wakeup(self):
with self._wake_lock:
Expand Down