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From "Michael Kjellman (JIRA)" <>
Subject [jira] [Commented] (CASSANDRA-13291) Replace usages of MessageDigest with Guava's Hasher
Date Mon, 13 Mar 2017 22:57:41 GMT


Michael Kjellman commented on CASSANDRA-13291:

Thanks Robert!

I've pushed up the changes to

 * Good catch on {{assertNotSame}} ... but there isn't actually {{assertNotEquals}}... Looks
like I need to do {{Assert.assertFalse}}
 * I had also thought about offline tools... but, I put {{MessagingService.CURRENT_HASH_FUNCTION}}
in {{MessagingService}} because of the logic like MessagingService.instance().areAllNodesAtLeast21()
to migrate the digest used during upgrade. So, I figured eventually the "current" one would
need to live in there anyways... It looks like we don't have this in trunk anymore because
maybe we don't have anything to migrate anymore? I feel like FBUtilities isn't a great place
because at some point we need to have it versioned.. thoughts?
 * I used {{JCAUtil}} because that is what the JDK was doing internally..... I figured it
was optimized in some way which is why the JDK was doing it that way... I'll just do it manually
for now as [~jasobrown] didn't like it either.

> Replace usages of MessageDigest with Guava's Hasher
> ---------------------------------------------------
>                 Key: CASSANDRA-13291
>                 URL:
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Michael Kjellman
>            Assignee: Michael Kjellman
>         Attachments: CASSANDRA-13291-trunk.diff
> During my profiling of C* I frequently see lots of aggregate time across threads being
spent inside the MD5 MessageDigest implementation. Given that there are tons of modern alternative
hashing functions better than MD5 available -- both in terms of providing better collision
resistance and actual computational speed -- I wanted to switch out our usage of MD5 for alternatives
(like adler128 or murmur3_128) and test for performance improvements.
> Unfortunately, I found given the fact we use MessageDigest everywhere --  switching out
the hashing function to something like adler128 or murmur3_128 (for example) -- which don't
ship with the JDK --  wasn't straight forward.
> The goal of this ticket is to propose switching out usages of MessageDigest directly
in favor of Hasher from Guava. This means going forward we can change a single line of code
to switch the hashing algorithm being used (assuming there is an implementation in Guava).

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