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From "Philippe Laflamme (JIRA)" <j...@apache.org>
Subject [jira] [Created] (TEPHRA-297) Inconsistent reads
Date Wed, 02 Jan 2019 17:25:00 GMT
Philippe Laflamme created TEPHRA-297:
----------------------------------------

             Summary: Inconsistent reads
                 Key: TEPHRA-297
                 URL: https://issues.apache.org/jira/browse/TEPHRA-297
             Project: Tephra
          Issue Type: Bug
    Affects Versions: 0.14.0-incubating
            Reporter: Philippe Laflamme
            Assignee: Poorna Chandra


It is possible to get inconsistent reads in the following test setup:
 * modify the BalanceBooks example to verify the balance periodically (say every second)
as opposed to only at the end.
 * start multiple transaction servers
 * start the modified BalanceBooks example
 * randomly restart the transaction servers

Running this for long enough will eventually lead to the balance verification to fail, reading
uncommitted or partially committed data.

The modified BalanceBooks example can be found here:

https://github.com/plaflamme/incubator-tephra/commit/6caeff5d76f193cdf2e0ad861059bc19cf894705

The logs of the various services can be found here: [https://gist.github.com/plaflamme/238a6539da9da1ac3a2e313e05ee82eb]

In my experimentation, I've found that this problem usually happens after the transaction
server fails to write its snapshot during shutdown. It may be unrelated, but this exception
usually shows up in the logs around the time when the issue is seen on the client.

This is the relevant section in the logs: [https://gist.github.com/plaflamme/238a6539da9da1ac3a2e313e05ee82eb#file-tephra-service-hbase-master-log-L1360-L1878]

I've sent a message to the mailing list about this problem: [https://mail-archives.apache.org/mod_mbox/tephra-dev/201812.mbox/%3CCAFYs7S9BgPs_A-1E-K3Q06BfiO7W%3Dh3mZD6-vkjb14R29C-bKw%40mail.gmail.com%3E] Sorry
for the noise, but perhaps a JIRA issue is more appropriate for discussing this.



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