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Zero-latency SQLite storage in every Durable Object

simonwillison.net

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Re: Zero-latency SQLite storage in every Durable Object

#51

Post by masterj »

klabb3 wrote: post #25
stavros wrote: post #3

This is a really interesting design, but these kinds of smart systems always inhabit an uncanny valley for me. You need them in exactly two cases: 1. You have a really high-load system that you need to figure out some clever ways to scale. 2. You're working on a toy project for fun. If #2, fine, use whatever you want, it's great. If this is production, or for Work(TM), you need something proven. If you don't know you…

Databases is an extremely slow-maturing area, similar to programming languages, but are all deviations from Postgres shiny and hipster? The idea of colocating data and behavior is really a quantifiable reduction in complexity. It removes latency and bandwidth concerns, which means both operational concerns and development concerns (famously the impact of the N+1 problem is greatly reduced). You can absolutely argue t…

If you adopt a wide-column db like Cassandra or DynamoDB, don’t you have to pick a shard for your table? The idea behind Durable Objects seems similar

Re: Zero-latency SQLite storage in every Durable Object

#52

Post by 8n4vidtmkvmk »

klabb3 wrote: post #25
stavros wrote: post #3

This is a really interesting design, but these kinds of smart systems always inhabit an uncanny valley for me. You need them in exactly two cases: 1. You have a really high-load system that you need to figure out some clever ways to scale. 2. You're working on a toy project for fun. If #2, fine, use whatever you want, it's great. If this is production, or for Work(TM), you need something proven. If you don't know you…

Databases is an extremely slow-maturing area, similar to programming languages, but are all deviations from Postgres shiny and hipster? The idea of colocating data and behavior is really a quantifiable reduction in complexity. It removes latency and bandwidth concerns, which means both operational concerns and development concerns (famously the impact of the N+1 problem is greatly reduced). You can absolutely argue t…

N+1 problem is also reduced if you keep your one and only server next to your one and only database.

This was actually the solution we came up with at a very big global company. Well, not 1 server, but 1 data center. If your write leaders are all in one place it apparently doesn't matter that everything else is global, for certain write requests at least.

Re: Zero-latency SQLite storage in every Durable Object

#53

Post by viraptor »

attilakun wrote: post #44
braden-lk wrote: post #36

Durable objects seem so cool but the pricing always scares me. (Specifically, having to worry about getting hibernation right.) They’d be a great fit for our yjs document based strategy, but while everything in prod still works on plain ol redis and Postgres, it’s hard to justify an exploration.

Does CloudFlare have proper spending caps? If they have, I'd be open to try DOs but if they don't, it's a non-starter for an indie dev as I can't risk bankruptcy due to a bad for loop.

It's not just the listed prices either. There was a story here not long ago where they essentially requested someone to migrate to an enterprise plan or get out. With AWS it's pretty common to get a refund for accidental abuse. From my contact so far and from stories here, I wouldn't expect anything close to that treatment from CF.

Re: Zero-latency SQLite storage in every Durable Object

#54

Post by skybrian »

stavros wrote: post #18
crabmusket wrote: post #15

Earlier quoted context omitted.

As far as I can tell, multiplayer is the killer app for Durable Objects. If you want to build another Figma, Google Docs, etc, the programming model of Durable Objects is super handy. This article goes into it more: https://digest.browsertech.com/archive/browsertech-digest-cl... I think this old article is quite relevant too: http://ithare.com/scaling-stateful-objects/ Anyone who read the Figma multiplayer article an…

That's a very interesting use case. Given that your "players" aren't guaranteed to be local to the DO, doesn't using DOs only make sense in high-traffic situations again? Otherwise you might as well just serve the players from a conventional server, no? CRDTs really do sound amazing, though.

Some games have regions and you only see players in the same region. For example, a “Europe” region. If you’re in the US and you connect to the Europe region, you know that you should expect some lag.

And it seems like that would work just as well with durable objects.

Re: Zero-latency SQLite storage in every Durable Object

#55

Post by simpsond »

masterj wrote: post #51
klabb3 wrote: post #25

Earlier quoted context omitted.

Databases is an extremely slow-maturing area, similar to programming languages, but are all deviations from Postgres shiny and hipster? The idea of colocating data and behavior is really a quantifiable reduction in complexity. It removes latency and bandwidth concerns, which means both operational concerns and development concerns (famously the impact of the N+1 problem is greatly reduced). You can absolutely argue t…

If you adopt a wide-column db like Cassandra or DynamoDB, don’t you have to pick a shard for your table? The idea behind Durable Objects seems similar

You have a row key, which gets consistently hashed to a shard / node on the ring.

Re: Zero-latency SQLite storage in every Durable Object

#56

Post by skybrian »

crabmusket wrote: post #32
emadda wrote: post #21

Some other interesting points: - The write api is sync, but it has a hidden async await: when you do your next output with a response, if the write fails the runtime will replace the response with a http failure. This allows the runtime to auto-batch writes and optimistically assume they will succeed, without the user explicitly handling the errors or awaits. - There are no read transactions, which would be useful to…

The RPC stuff is pretty interesting. More here: https://blog.cloudflare.com/javascript-native-rpc/

Without a schema, I’m wondering about validation. I guess your server should use Zod or an equivalent library?

Re: Zero-latency SQLite storage in every Durable Object

#57

Post by tmikaeld »

> ..each DO constantly streams a sequence of WAL entries to object storage - batched every 16MB or every ten seconds.

Which also means it may take 10 seconds before you can (reliably) read the write globally.

I keep failing to see how this can replace regionally placed database clusters which can serve a continent in milliseconds.

Edit: I know it uses streams, but those are only to 5 followers and CF have hundreds of datacenters. There is no physical way to guarantee reads in seconds unless all instances of the SQLite are always connected and even then, packet latency will cause issues.

Re: Zero-latency SQLite storage in every Durable Object

#58

Post by tlarkworthy »

crabmusket wrote: post #27
stavros wrote: post #18

Earlier quoted context omitted.

That's a very interesting use case. Given that your "players" aren't guaranteed to be local to the DO, doesn't using DOs only make sense in high-traffic situations again? Otherwise you might as well just serve the players from a conventional server, no? CRDTs really do sound amazing, though.

Best case, the players are co-located in a city or country, and they'll benefit from data center locality. Worst case, they're not co-located, and one participant has good latency, and the other doesn't. This is equivalent to the "deploy the backend in a single server/datacenter" approach. Aside from the data locality, I still find the programming model (a globally-unique and addressable single-threaded class instanc…

It's the actor model essentially.

You can have a DO proxy each user connection, then they forward messages to the multipler document. The user proxy deals with ordering and buffering their connection message state in the presence of disconnects, and the document DO handles the shared state.

Re: Zero-latency SQLite storage in every Durable Object

#59

Post by aldonius »

crabmusket wrote: post #31
fracus wrote: post #14

Earlier quoted context omitted.

Could this be used to get a time edge in trading? I'm not an expert, just thinking out loud. I remember hearing about firms laying wire in a certain way because getting a microsecond jump on changing rates could be everything for them.

I'm also no expert, but from reading around the subject a little (Flash Boys by Michael Lewis was pretty cool, also Jane Street's podcast has some fantastic information)... no. I doubt you'd be on a public cloud if low-latency trading is what you're doing.

Aren't the HFT boxes usually stock exchange colocations? Each trader gets a rack (or multiple racks depending on size) in the exchange's datacenter, every rack has the same cable length to the switch, etc.

Re: Zero-latency SQLite storage in every Durable Object

#60

Post by neamar »

tmikaeld wrote: post #57

> ..each DO constantly streams a sequence of WAL entries to object storage - batched every 16MB or every ten seconds. Which also means it may take 10 seconds before you can (reliably) read the write globally. I keep failing to see how this can replace regionally placed database clusters which can serve a continent in milliseconds. Edit: I know it uses streams, but those are only to 5 followers and CF have hundreds of…

The writes are streamed in near real time to five followers, acknowledging it near instantly. The cloudflare blog article mention this more in depth. So writes remain fast, while still having durability.
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