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From "Philip Thompson (JIRA)" <j...@apache.org>
Subject [jira] [Created] (CASSANDRA-10117) FD Leak with DTCS
Date Tue, 18 Aug 2015 17:09:45 GMT
Philip Thompson created CASSANDRA-10117:
-------------------------------------------

             Summary: FD Leak with DTCS
                 Key: CASSANDRA-10117
                 URL: https://issues.apache.org/jira/browse/CASSANDRA-10117
             Project: Cassandra
          Issue Type: Bug
            Reporter: Philip Thompson
            Assignee: Benedict
             Fix For: 2.1.x
         Attachments: fd.log

Using 2.1-HEAD, specifically commit 972ae147247a, I am experiencing issues in a one node test
with DTCS. These seem separate from CASSANDRA-9882. 

Using an ec2 i2.2xlarge node with all default settings and the following schema:

{code}
CREATE KEYSPACE ks WITH replication = {'class': 'SimpleStrategy', 'replication_factor': 1};

  CREATE TABLE tab (
      key uuid,
      year int,
      month int,
      day int,
      c0 blob,
      c1 blob,
      c2 blob,
      c3 blob,
      c4 blob,
      c5 blob,
      c6 blob,
      c7 blob,
      c8 blob,
      PRIMARY KEY ((year, month, day), key)
  ) WITH compaction = {'class': 'org.apache.cassandra.db.compaction.DateTieredCompactionStrategy'};
{code}

I loaded 4500M rows via stress, which totaled ~1.2TB. I then performed a few mixed workloads
via stress, which were 50% insert, 50% the following read: {{Select * from tab where year
= ? and month = ? and day = ? limit 1000}}.

This was done to reproduce a separate issue for a user. I then received reports from the user
that they were experiencing open FD counts per sstable in the thousands. With absolutely no
load on my cluster, I was finding that any sstable with open FDs had between 243 and 245 open
FDs. I then started a stress process performing the same read/write workload as before. I
was then immediately seeing FD counts as high as 6615 for a single sstable.

I was determining FD counts per sstable with the following [example] call:
{{lsof | grep '16119-Data.db' | wc -l}}.

I still have this cluster running, for you to examine. System.log is attached.



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