In-memory SQLite databases don't use WAL. Wasm (and browser Wasm, in particular) doesn't support anything like the shared memory APIs SQLite wants for its WAL mode.
Litestream requires a very precise WAL setup to work (which just so happens to work with the default native SQLite setup, but is hard to replicate with Wasm).
Cloudflare Durable Objects may have been inspired by Litestream but works very differently (as do LiteFS, Turso, etc…)
The general idea of streaming changes from SQLite would work, but it's a lot of work, and the concurrency model of in-browser Wasm will make it challenging to implement.
(I wrote that forum post some time ago, and have WAL working in a server side Wasm build of SQLite, but none of the options to make it work would make much sense, or be possible, in browser)
I'm gathering that I need to learn about: - WAL - Shared Memory APIs - Concurrency models - Durable Objects?
concurrency model of in-browser Wasm: https://medium.com/@quincarter/wasm-is-awsm-and-multi-thread...
Cloudflare Durable Objects: https://www.cloudflare.com/developer-platform/durable-object...
Shared memory API: If you want to share (mutable) data between multiple processes, you need some kind of procedure in place to manage that. How do you get a reference to the data to multiple processes, how do you make sure they don't trample each other's writes, etc.
Concurrency model: There are many different ways you can formalize concurrent processes and the way they interact (message passing, locking, memory ordering semantics, etc.). Different platforms will expose different concurrency primitives that may not work the same way as other platforms and may require different reasoning or code structure
Durable objects - I think this is some Cloudflare service where they host data that can be read or modified by your users
This is all from memory, but IME, GPT is pretty good for asking about concepts at this level of abstraction
And side note on your last point - I've been burned too many times by confident hallucinations to trust my foundational learning to GPT. I hope someday that will improve, but for now ChatGPT is as trustworthy as an evening chat with someone at the bar.
... Someone who has been drinking since happy hour.
Our database API is modeled on CouchDB and MongoDB, but our storage abstractions are along the lines of what you need to build the multi writer WAL you describe.
More details here https://jsr.io/@fireproof/encrypted-blockstore
I dunno, feels like you're coming down too hard.
https://sqlite.org/wasm/doc/trunk/persistence.md#opfs-wal
Again, just because the all the Lego pieces sound like they should all just fit together, doesn't mean that they will.
The VFS mechanism was primarily designed to make SQLite easy to port to multiple OSes. WAL mode is hard to port everytime you step away from a more traditional OS.
“We have SQLite in the browser, let's just stream the WAL like the Litestream hack” does not add up.
It's not impossible, but it surely took a lot of effort at Cloudflare (or at Fly, or Turso) to get there. And neither of them opened it up sufficiently to help us do the same. In a browser.