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https://issues.apache.org/jira/browse/CASSANDRA-7392?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14790764#comment-14790764
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Ariel Weisberg edited comment on CASSANDRA-7392 at 9/16/15 9:00 PM:
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bq. I also prefer to re-introduce the CAS in MonitoringStateRef: if the worker
thread does not notice that the query was aborted it will carry on iterating
which defeats the purpose of aborting the queries.
Is that really an issue? It just indicates it's barely timing out. It might
time out in a subsequent iteration. Timeouts are inherently approximate. Why
pay a cost on every transaction for something that isn't usually expected to
happen?
When you mean doesn't notice it was aborted, you mean it completes one of these
subqueries and then is issued the next one? It would notice while processing an
individual query regardless of CAS or lazySet. They both become globally
visible at the same speed so CAS isn't going to do better.
bq. It's also worse than this. I didn't realize that the CQL string
reconstructed from ReadCommand is really an approximation as we don't have all
the information there. For example, a query without a condition on the primary
key will be split in several queries as follows:
I don't see that as much of an issue other than being confusing to the reader
as to what the user visible query was associated with. The queries are all the
same structure so if we could aggregate we would hide this anyways.
Some other databases log every slow query so this is fine as a starting point.
was (Author: aweisberg):
bq. I also prefer to re-introduce the CAS in MonitoringStateRef: if the worker
thread does not notice that the query was aborted it will carry on iterating
which defeats the purpose of aborting the queries.
Is that really an issue? It just indicates it's barely timing out. It might
time out in a subsequent iteration. Timeouts are inherently approximate. Why
pay a cost on every transaction for something that isn't usually expected to
happen?
When you mean doesn't notice it was aborted, you mean it completes one of these
subqueries and then is issued the next one? It would notice while processing an
individual query regardless of CAS or lazySet. They both become globally
visible at the same speed so CAS isn't going to better.
bq. It's also worse than this. I didn't realize that the CQL string
reconstructed from ReadCommand is really an approximation as we don't have all
the information there. For example, a query without a condition on the primary
key will be split in several queries as follows:
I don't see that as much of an issue other than being confusing to the reader
as to what the user visible query was associated with. The queries are all the
same structure so if we could aggregate we would hide this anyways.
Some other databases log every slow query so this is fine as a starting point.
> Abort in-progress queries that time out
> ---------------------------------------
>
> Key: CASSANDRA-7392
> URL: https://issues.apache.org/jira/browse/CASSANDRA-7392
> Project: Cassandra
> Issue Type: New Feature
> Components: Core
> Reporter: Jonathan Ellis
> Assignee: Stefania
> Priority: Critical
> Fix For: 3.x
>
>
> Currently we drop queries that time out before we get to them (because node
> is overloaded) but not queries that time out while being processed.
> (Particularly common for index queries on data that shouldn't be indexed.)
> Adding the latter and logging when we have to interrupt one gets us a poor
> man's "slow query log" for free.
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