Streams and Reminders underlying implementation (hash ring) about erleans

[cmeiklejohn]

What are the downsides of hash_ring? I don't know much about it.

[tsloughter]

I actually don't know that there is a downside. But that is because I know little about it. There doesn't seem to be much use of it by others, and no one had suggested it to me, I simply found it when searching hex.pm for libs.

So on further review it may be fine. And assuming it is still a decent solution to have each node seperately react to cluster changes (currently through net_kernel but going to change that to using the partisan event handler) and calculate the new hash ring independently then we may simply stick to this.

[cmeiklejohn]

I'm a bit scared just picking libraries off of GitHub/Hex without investigation. When we picked up zraft_lib we ran into problems of linearization violations, which, is problematic for a consensus protocol. So, I'd highly recommend, if we decide to use the library, that we perform due diligence.

[tsloughter]

Yup, agreed.

[evanmcc]

There's also https://github.com/ferd/lrw, which I don't know if it's done a lot of real-world work, we at least know the author.

[ferd]

That's running session affinity at heroku so at least it's seen consistent load for a couple of years.

[evanmcc]

sorry, Fred, I forgot about that one.

[tsloughter]

I don't think lrw will work for how I'd like this to work. It doesn't currently do this but since streams and reminders are persisted to storage we can include a "vnode" field to index on. Then when the distribution of vnodes changes each node simply has to fetch all streams/reminders from storage with vnode=x,y,z...

[tsloughter]

One @Licenser had pointed me to is https://github.com/darach/jch-erl if anyone has any opinion on it.