4 ms·

There are definitely solutions for handling this with consistency semantics that are something weaker than linearizable consistency. But they usually become exp

There are definitely solutions for handling this with consistency semantics that are something weaker than linearizable consistency. But they usually become expensive in other ways and loose a lot of the availability benefits to recover the consistency properties you do need. Most of the models we're even talking about here are something in the realm of sequential or causal consistency, which are still considered strong consistency models (and are usually implemented on top of linearizable algorithms that allow for weakening invariants that protect against witnessing inconsistency. spanner is an example of this). Your friend-state solution only protects the visibility of the post if the friend-state between the two users has not changed more recently than both the post and your version. I.E. Friend state 0 is we're friends. Friend state 1 is we're not friends. Friend state 2 is we're friends. Friend state 3 is we're not friends. I have friend state 2, and the post is at state 1. I accept my version incorrectly and am able to view the post, despite the fact that we're no longer friends.

wpietri 10y ago
Do you perhaps have a different example that might make the problem more apparent here? Because if I post something you don't want to see, give you permission to see it, and then take it away again, I can live with you seeing it. I probably won't even know if you saw it because there was some sort of system glitch or if you just happened to look during friend state 2.
betenoire 10y ago
I'm seeing a lot of comments that are basically saying, "we don't need no stinking transactions because we can mostly reinvent them in the app." And the point of the article was, yeah, or you could pick a solution that already solves this.
- wpietri 10y ago
  Was that the point of the article? I didn't read it that way. E.g.: "In conclusion, if you use micro-services or NoSQL databases, do your homework! Choose appropriate boundaries for your systems."
  - betenoire 10y ago
    You are right. The article says to understand your choice, it doesn't say WHAT to choose. Pretty sure the subtext is that developers are making their lives harder than they need to by not understanding the choice they are making.

wpietri 10y ago

Do you perhaps have a different example that might make the problem more apparent here? Because if I post something you don't want to see, give you permission to see it, and then take it away again, I can live with you seeing it. I probably won't even know if you saw it because there was some sort of system glitch or if you just happened to look during friend state 2.

betenoire 10y ago

I'm seeing a lot of comments that are basically saying, "we don't need no stinking transactions because we can mostly reinvent them in the app." And the point of the article was, yeah, or you could pick a solution that already solves this.

wpietri 10y ago
Was that the point of the article? I didn't read it that way. E.g.: "In conclusion, if you use micro-services or NoSQL databases, do your homework! Choose appropriate boundaries for your systems."
- betenoire 10y ago
  You are right. The article says to understand your choice, it doesn't say WHAT to choose. Pretty sure the subtext is that developers are making their lives harder than they need to by not understanding the choice they are making.