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PYTHON-438 - Add option to populate parital QueryTrace #428

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Merged
aholmberg merged 1 commit into from
Nov 3, 2015
Merged

PYTHON-438 - Add option to populate parital QueryTrace #428

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15 changes: 11 additions & 4 deletions cassandra/query.py
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Original file line number Diff line number Diff line change
Expand Up @@ -858,14 +858,17 @@ def __init__(self, trace_id, session):
self.trace_id = trace_id
self._session = session

def populate(self, max_wait=2.0):
def populate(self, max_wait=2.0, wait_for_complete=True):
"""
Retrieves the actual tracing details from Cassandra and populates the
attributes of this instance. Because tracing details are stored
asynchronously by Cassandra, this may need to retry the session
detail fetch. If the trace is still not available after `max_wait`
seconds, :exc:`.TraceUnavailable` will be raised; if `max_wait` is
:const:`None`, this will retry forever.

`wait_for_complete=False` bypasses the wait for duration to be populated.
This can be used to query events from partial sessions.
"""
attempt = 0
start = time.time()
Expand All @@ -879,15 +882,19 @@ def populate(self, max_wait=2.0):
session_results = self._execute(
self._SELECT_SESSIONS_FORMAT, (self.trace_id,), time_spent, max_wait)

if not session_results or session_results[0].duration is None:
is_complete = session_results[0].duration is not None
if not session_results or (wait_for_complete and not is_complete):
time.sleep(self._BASE_RETRY_SLEEP * (2 ** attempt))
attempt += 1
continue
log.debug("Fetched trace info for trace ID: %s", self.trace_id)
if is_complete:
log.debug("Fetched trace info for trace ID: %s", self.trace_id)
else:
log.debug("Fetching parital trace info for trace ID: %s", self.trace_id)

session_row = session_results[0]
self.request_type = session_row.request
self.duration = timedelta(microseconds=session_row.duration)
self.duration = timedelta(microseconds=session_row.duration) if is_complete else None
self.started_at = session_row.started_at
self.coordinator = session_row.coordinator
self.parameters = session_row.parameters
Expand Down