To keep long-running queries or idle sessions from tying up cluster
resources, you can set timeout intervals for both individual queries, and
entire sessions.
-
In Cloudera Manager, navigate to .
- In the search field, type
idle.
- In the Idle Query Timeout field, specify
the time in seconds after which an idle query is cancelled.
This could be a query whose results were all fetched but was never
closed, or one whose results were partially fetched and then the
client program stopped requesting further results. This condition is
most likely to occur in a client program using the JDBC or ODBC
interfaces, rather than in the interactive
impala-shell interpreter. Once a query is
cancelled, the client program cannot retrieve any further results
from the query.
You can reduce the idle query timeout by using the
QUERY_TIMEOUT_S query option at the query level.
Any non-zero value specified in this field serves as an upper limit
for the QUERY_TIMEOUT_S query option.
The value of 0 disables query timeouts.
- In the Idle Session Timeout field,
specify the time in seconds after which an idle session expires.
A session is idle when no activity is occurring for any of the
queries in that session, and the session has not started any new
queries. Once a session is expired, you cannot issue any new query
requests to it. The session remains open, but the only operation you
can perform is to close it.
The default value of 0 specifies sessions never expire.
You can override this setting with the
IDLE_SESSION_TIMEOUT query option at the session
or query level.
- Click Save Changes and restart
Impala.
Impala checks periodically for idle sessions
and queries to cancel. The actual idle time before cancellation might be
up to 50% greater than the specified configuration setting. For example,
if the timeout setting was 60, the session or query might be cancelled
after being idle between 60 and 90 seconds.
