Note that 0x3D is the "=" character in ASCII, so "=3D" in QP is "=" in ASCII. :)
This email has probably been through a few conversions to QP and back again between different email clients. Perhaps some buggy client got confused between an ASCII "=" and a QP escape sequence or something like that.
Another FYI type comment I guess. :) Some of my more gripey statements here may be outdated info, so DYOR I guess.
Dynamic reconfig in 3.5 addresses the "restarting every zookeeper instance" problem. [0] You stand up an initial quorum with seed config, then tie in new servers with "reconfig -add". Not sure how well it would tie into cloudy autoscaling stuff though. I wouldn't start there myself.
A much bigger pain IMO is the handling of DNS in the official Java ZK client earlier than 3.4.13/3.5.5 (and by association, Curator, ZkClient, etc.). [1] The former was released mid 2018 and the latter this year, so tons of stuff out there that just won't find a host if IPs change. If you "own" all the clients it's maybe not a problem, but if you've got a lot of services owned by a ton of teams it's ... challenging.
Even with the fix for ZOOKEEPER-2184 in place I'm pretty sure DNS lookups are only retried if a connect fails, so there's still the issue of IPs "swapping" unexpectedly at the wrong time in cloud environments which can lead to a ZK server in cluster A talking to a ZK server in cluster B (or worse: clients of cluster A talking to cluster B mistakenly thinking that they're talking to cluster A). I'm sure this problem's not unique to ZK though.
Authentication helps prevent the worst-case scenarios, but I'm not sure if it helps from an uptime perspective.
TL;DR: ZK in the cloud can get messy (even if you play it relatively "safe").
> I think you’re retroactively claiming that Google actively anticipated this in their choice at the beginning of using Perforce as an SCM.
Oh I didn't mean to imply exactly that, but really good point. I just meant that it seems like folks don't typically _anticipate_ these issues so much as they're forced into it by ossifying velocity in the face of sudden wild success. I know at least a few examples of this happening -- but you're right, those folks were using Git.
In Google's case, maybe it's simply that their centralized VCS led them down a certain path, their tooling grew out of that & they came to realize some of the benefits along the way. I'd be interested to know too. :)
Exactly this. Or at least it's a way this can be achieved, assuming solid testing & some tooling in the mix.
For folks unfamiliar with it, the issue is something like:
1. You find a bug in a library A.
2. Libraries B, C and D depend on A.
3. B, C and D in turn are used by various applications.
How do you fix a bug in A? Well, "normal" workflow would be something like: fix the bug in A, submit a PR, wait for a CI build, get the PR signed off, merge, wait for another CI build, cut a release of A. Bump versions in B, C and D, submit PRs, get them signed off, CI builds, cut a release of each. Now find all users of B, C and D, submit PRs, get them signed off, CI builds, cut more releases ...
Now imagine the same problem where dependency chains are a lot more than three levels deep. Then throw in a rat's nest of interdependencies so it's not some nice clean tree but some sprawling graph. Hundreds/thousands of repos owned by dozens/hundreds of teams.
See where this is going? A small change can take hours and hours just to make a fix. Remember this pain applies to every change you might need to make in any shared dependency. Bug fixes become a headache. Large-scale refactors are right out. Every project pays for earlier bad decisions. And all this ignores version incompatibilities because folks don't stay on the latest & greatest versions of things. Productivity grinds to a halt.
It's easy to think "oh, well that's just bad engineering", but there's more to it than that I think. It seems like most companies die young/small/simple & existing dependency management tooling doesn't really lend itself well to fast-paced internal change at scale.
So having run into this problem, folks like Google, Twitter, etc. use monorepos to help address some of this. Folks like Netflix stuck it out with the multi-repo thing, but lean on tooling [0] to automate some of the version bumping silliness. I think most companies that hit this problem just give up on sharing any meaningful amount of code & build silos at the organizational/process level. Each approach has its own pros & cons.
Again, it's easy to underestimate the pain when the company is young & able to move quickly. Once upon a time I was on the other side of this argument, arguing against a monorepo -- but now here I am effectively arguing the opposition's point. :)
Note that 0x3D is the "=" character in ASCII, so "=3D" in QP is "=" in ASCII. :)
This email has probably been through a few conversions to QP and back again between different email clients. Perhaps some buggy client got confused between an ASCII "=" and a QP escape sequence or something like that.