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From André Cruz (JIRA) <j...@apache.org>
Subject [jira] [Created] (CASSANDRA-5143) Safety valve on number of tombstones skipped on read path too prevent a full heap
Date Thu, 10 Jan 2013 18:48:15 GMT
André Cruz created CASSANDRA-5143:
-------------------------------------

             Summary: Safety valve on number of tombstones skipped on read path too prevent
a full heap
                 Key: CASSANDRA-5143
                 URL: https://issues.apache.org/jira/browse/CASSANDRA-5143
             Project: Cassandra
          Issue Type: Improvement
          Components: Core
    Affects Versions: 1.1.5
         Environment: Debian Linux, 3 node cluster with RF 3, 8GB heap on 32GB machines
            Reporter: André Cruz


When doing a range query on a row with a lot of tombstones, these can quickly add up and use
too much heap, even if we specify a column count of 2 as the tombstones can be between those
two live columns. From the client API side it can do nothing to prevent this from happening
since there is no limit that can be specified for the number of tombstones being collected.

I know that this looks like the "I'm using a row as a queue and building up a ton of tombstones"
anti-pattern, but still Cassandra should be able to take better care of himself so as to prevent
a DoS. I can imagine a lot of use cases that let users create and delete columns on a row.

I propose a simple safety valve that can act like this: "The client has asked me for X nodes,
I've already collected X^Y nodes and still have not found X live nodes, I should just give
up". The Y would be the configurable parameter. Time taken per query or memory used could
also be factors to take into consideration.

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