Hacker News Reader

Comment by PeterZaitsev | Hacker News Reader

I think one thing Andy misses about why people were pissed about Elastic and Redis but not as many for MongoDB and some other is their license and size of Contributors Community.

When original license is as restricted as AGPL it is unlikely there is much of embedded use... so less people are impacted in truly catastrophic way

Also if there is no contributor community to speak of... who is going to do the fork ?

I put some thoughts about it in my post about ScyllaDB https://peterzaitsev.com/thoughts-on-scylladb-license-change...

View on HN

> In the case of Redis, I can only think that people perceive Redis Ltd. as unfairly profiting off others' work since the company's founders were not the system's original creators. An analysis of Redis' source code repository also shows that a sizable percentage of contributions to the DBMS comes from outside the company

He mentions this in "Andy’s Take" section btw

Yes. Not the license though.

RE ScyllaDB, there will absolutely be no fork and it’s very unlikely they have ever had a meaningful contribution to Scylla OSS (which is not changing, just going to bit rot and the enterprise version which was closed source was moved to source available). The reasoning being the bar is very high for contributions. It’s C++ 20/23 without virtual memory and a userland cooperative thread per core scheduler (this is the underlying seastar framework). The skills needed to do anything meaningful here is very high and I don’t see the motivation behind it as I would expect people having feature requests would be customers, have an easier time extending Cassandra or the feature would be available in the Enterprise version.

> It’s C++ 20/23 without virtual memory

Not sure what you mean by this? Virtual memory is implied by the CPU MMU and consequently OS kernel. Perhaps you meant they use a lot of custom memory allocation schemes?

Otherwise, I agree that the bar is quite high since (1) the problem at hand is already too complex (scalable LSM), and (2) pretty much anything in the code is custom made, e.g. avoiding the OS kernel as much as possible. And they pay peanuts for the skills needed to do the job.

Seastar runs everything in kernel mode.

It tries to bypass the kernel as much as possible. It runs in userspace.

I'm probably thinking of when it's combined with OSv or something. It's been years since I looked at this.

Makes no sense. Source?

I mean memory is completely allocated up front and fragmentation is something for application developers to deal with.

I occasionally read their blogs, and I haven't looked into the source for a while, but application developers having to deal with the OOM because one is using custom memory allocation policy that doesn't deal with or suffers from fragmention would be a strange design choice.

jmalloc IME works really well.

Reply on news.ycombinator.com