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https://issues.apache.org/jira/browse/HBASE-21256?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16632977#comment-16632977
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Duo Zhang commented on HBASE-21256:
-----------------------------------
{quote}
It is 48-bits seed algorithm (according to HBASE-13382 said) that Random
utilizes and therefore it CAN generated 32-bits numbers in a completely random
way.
{quote}
Not really. In HBASE-13161 it shows that SecureRandom can fix the problem.
Anyway, the SecureRandom is not necessary as we do not need 'secure' here.
See this page
https://en.wikipedia.org/wiki/Linear_congruential_generator
There is a table which shows different parameter for different LCGs, I think we
could make use of the one introduced by Knuth. It uses a 64 bits seed, so we
can use it to generate our 16 bytes key - just use two longs, and we can make
sure that a 10B test will not have collisions, as we need to generate 2^64
times to make it repetitive.
Thanks.
> Improve IntegrationTestBigLinkedList for testing huge data
> ----------------------------------------------------------
>
> Key: HBASE-21256
> URL: https://issues.apache.org/jira/browse/HBASE-21256
> Project: HBase
> Issue Type: Improvement
> Components: integration tests
> Affects Versions: 3.0.0
> Reporter: Zephyr Guo
> Assignee: Zephyr Guo
> Priority: Major
> Fix For: 3.0.0
>
> Attachments: HBASE-21256-v1.patch, ITBLL-1.png, ITBLL-2.png
>
>
> Recently, I use ITBLL to test some features in our company. I have
> encountered the following problems:
>
> 1. Generator is too slow at the generating stage, the root cause is
> SecureRandom. There is a global lock in SecureRandom( See the following
> picture). I use Random instead of SecureRandom, and it could speed up this
> stage(500% up with 20 mapper). SecureRandom was brought by HBASE-13382, but
> speaking of generating random bytes, in my opnion,
> it is the same with Random.
> !ITBLL-1.png!
> 2. VerifyReducer have a cpu cost of 14% on format method. This is cause by
> create keyString variable. However, keyString may never be used if test
> result is correct.(and that's in most cases). Just delay creating keyString
> can yield huge performance boost in verifing stage.
> !ITBLL-2.png!
> 3.Arguments check is needed, because there's constraint between arguments. If
> we broken this constraint, we can not get a correct circular list.
>
> 4.Let big family value size could be configured.
>
> 5.Avoid starting RS at backup master
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