Tim Armstrong created IMPALA-7115:
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Summary: Set a default THREAD_RESERVATION_LIMIT value
Key: IMPALA-7115
URL: https://issues.apache.org/jira/browse/IMPALA-7115
Project: IMPALA
Issue Type: Improvement
Components: Backend
Reporter: Tim Armstrong
Assignee: Tim Armstrong
As a follow on to IMPALA-6035, we should set a default value that actually will
help protect again insanely complex queries.
Motivating discussion is here:
https://gerrit.cloudera.org/#/c/10365/9/common/thrift/ImpalaInternalService.thrift
{quote}
Tim Armstrong
1:11 PM
Dan suggested setting a default here. I started doing some experiments to see
what our current practical limits are.
On stock Ubuntu 16.04 I start getting thread_resource_error at around 8000
reserved threads. I'm not sure that the config reflects what people would use
on production systems so continuing to investigate.
Dan Hecht
1:31 PM
We could also consider choosing a default dynamically based on the OS's
setting, if that's necessary.
Tim Armstrong
3:45 PM
I increased some of the configs (I think I was limited by
/sys/fs/cgroup/pids/user.slice/user-1000.slice/pids.max == 12288) and now it
got oom-killed at ~26000 threads.
I think unfortunately there are a lot of different OS knobs that impact this
and they seem to evolve over time, so it's probably not feasible with a
reasonable amount of effort to get it working on all common Linux distros.
I was thinking ~5000, since 1000-2000 plan nodes is the most I've seen for a
query running successfully in production.
Maybe I should do this in a follow-on change, since we probably also want to
add a test query at or near this limit.
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