4 ms·

Weird thing I have been seeing on Reddit is comment upvotes being off-by-one periodically on page refreshes. Reload, you get 3. Reload again, you get 4. Again,

Weird thing I have been seeing on Reddit is comment upvotes being off-by-one periodically on page refreshes. Reload, you get 3. Reload again, you get 4. Again, you get 3. Seems like a replication issue?

kondor6c 9y ago
I believe they are using cassandra to store the upvotes
- ketralnis 9y ago
  That one is in postgres
- sverhagen 9y ago
  Just curious if this is a stab at Cassandra, or whether use of Cassandra would automatically imply eventual consistency or something else that would appear in this way?
  - ketralnis 9y ago
    Cassandra as it's often used can imply eventual consistency (e.g. counter incrs with CL.ONE) but "eventual" in this case would be in the range of 10's of ms That said, reddit's upvote counters in particular are stored in Postgres, not Cassandra
kelnage 9y ago
> Weird thing I have been seeing on Reddit is comment upvotes being off-by-one periodically on page refreshes. Reload, you get 3. Reload again, you get 4. Reload, you get 3. Seems like a replication issue? This is done on purpose [1], to prevent bots from calculating exact post/comment scores. 1. https://www.reddit.com/wiki/faq#wiki_how_is_a_comment.27s_score_determined.3F https://www.reddit.com/wiki/faq#wiki_how_is_a_comment.27s_sc...
- Xeoncross 9y ago
  I still don't understand what purpose this feature has - can you explain more?
  - Gaelan 9y ago
    A votebot suspects that it is being detected and filtered out of the final scores. Because the scores fluctuate, it is harder to determine if your vote had an impact.
    - wordupmaking 9y ago
      But that doesn't "prevent spambots etc.", that merely prevents people from easily and instantly figuring out whether their bots are detected yet. It doesn't stop them from spamming votes, or from making their bots more elaborate regardless of whether they have been detected yet. I don't know all the motivations for spam bots or how people who make them tick, but I'd figure for a significant number the crucial bit is having an impact, not measuring it. Most spam is fire and forget, after all.
      - sanswork 9y ago
        The point isn't to prevent them which is near on impossible but to get them to waste enough resources on non-visible actions regularly enough that it isn't economically viable to continue trying to spam the site.
        joombaga 9y ago
        Even so, I think GP's point is still valid in that it doesn't achieve that desired effect, but of course Reddit has those stats and I do not.
      - rhizome 9y ago
        "There's no silver bullet." --Fred Brooks
  - 9y ago
samtho 9y ago
That's vote fuzzing you're seeing. It's to prevent people (read: bots) from being able to tell if they are shadowbanned.

kondor6c 9y ago

I believe they are using cassandra to store the upvotes

ketralnis 9y ago
That one is in postgres
sverhagen 9y ago
Just curious if this is a stab at Cassandra, or whether use of Cassandra would automatically imply eventual consistency or something else that would appear in this way?
- ketralnis 9y ago
  Cassandra as it's often used can imply eventual consistency (e.g. counter incrs with CL.ONE) but "eventual" in this case would be in the range of 10's of ms That said, reddit's upvote counters in particular are stored in Postgres, not Cassandra

kelnage 9y ago

> Weird thing I have been seeing on Reddit is comment upvotes being off-by-one periodically on page refreshes. Reload, you get 3. Reload again, you get 4. Reload, you get 3. Seems like a replication issue? This is done on purpose [1], to prevent bots from calculating exact post/comment scores. 1. https://www.reddit.com/wiki/faq#wiki_how_is_a_comment.27s_score_determined.3F https://www.reddit.com/wiki/faq#wiki_how_is_a_comment.27s_sc...

Xeoncross 9y ago
I still don't understand what purpose this feature has - can you explain more?
- Gaelan 9y ago
  A votebot suspects that it is being detected and filtered out of the final scores. Because the scores fluctuate, it is harder to determine if your vote had an impact.
  - wordupmaking 9y ago
    But that doesn't "prevent spambots etc.", that merely prevents people from easily and instantly figuring out whether their bots are detected yet. It doesn't stop them from spamming votes, or from making their bots more elaborate regardless of whether they have been detected yet. I don't know all the motivations for spam bots or how people who make them tick, but I'd figure for a significant number the crucial bit is having an impact, not measuring it. Most spam is fire and forget, after all.
    - sanswork 9y ago
      The point isn't to prevent them which is near on impossible but to get them to waste enough resources on non-visible actions regularly enough that it isn't economically viable to continue trying to spam the site.
      - joombaga 9y ago
        Even so, I think GP's point is still valid in that it doesn't achieve that desired effect, but of course Reddit has those stats and I do not.
    - rhizome 9y ago
      "There's no silver bullet." --Fred Brooks
- 9y ago

samtho 9y ago

That's vote fuzzing you're seeing. It's to prevent people (read: bots) from being able to tell if they are shadowbanned.