Litestream Writable VFS

I need to bring writes to my version of the VFS.

I'm still waiting on how they'll prevent accidental corruption from multiple writers; there's a PR implementing write leases, not sure if that's the direction they'll take.

That said, pausing local polling when writes are enabled - i.e. assuming you're the only writer - makes sense, it's a good idea; hadn't occurred to me.

Ideally, I'd like to offer durability on fullfsync. I think this is feasible. In a concurrent system (single host), while a writer is waiting for durability confirmation, readers can continue reading the previous state, and the next writer can read the committed - but not yet durable - data and queue its writes to be batched. You can have as many pending writes as you're willing to have connections.

	▲	benbjohnson an hour ago \| parent [-]
		Litestream author here. Currently we're handling the "single writer" issue outside of Litestream. We have controls in our internal systems that make it work well. But yes, the lease PR is the direction we're looking at going. I'm not sure you can have readers see something separate than writers. When SQLite promotes a read lock to a write lock under WAL then it checks if any of the data has changed and then fails the transaction if it has.

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joshstrange an hour ago | parent | prev | next [-]

I glad this got re-upped, I was sad there wasn't much (any?) discussion when this was posted a few days ago.

I find the ways people extend or build on top of Sqlite to be fascinating. I use it in a few apps but not on the server (yet). Multi-writer for something like would be amazing (incredibly difficult to do well, obviously). I work on a home-rolled distributed database (multi-writer) but it has numerous downsides/issues so I love seeing how other people approach and solve these things.

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xrd 3 hours ago | parent | prev | next [-]

I love litestream. I've used it with pocketbase and it works. sqlite is a great building block for almost everything.

Does anyone know whether you could use this to stitch together a bunch of .db files (that share the same schema) in an ad-hoc way?

For example, if I decided I wanted to synchronize my friend's .db file, could I enable this using litestream? And, what if my friend wanted to sync two of his friends' .db files, but I'm only interested in his changes, not theirs? I assume this kind of fan out is not possible, but it would be fun if so.

	▲	benbjohnson an hour ago \| parent [-]
		If you can have multiple writers to a single database then you'd need to look at something like cr-sqlite[1] that uses CRDT to figure out conflicts. If you're just replicating separate databases then you might be able to replicate each one using Litestream and then use SQLite's ATTACH[2] to connect them together. There is a limit on how many databases you can attach together in a session though. [1]: https://github.com/vlcn-io/cr-sqlite [2]: https://sqlite.org/lang_attach.html

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skybrian an hour ago | parent | prev | next [-]

I’m a hobbyist who doesn’t have any s3-compatible storage. (That I know of, anyway.) What’s the easiest way to try it out?

	▲	benbjohnson an hour ago \| parent \| next [-]
		Litestream author here. You can use the built-in file replication. It'll replicate all your database changes to another path on disk. I use it a lot for testing things out: https://litestream.io/guides/file/
	▲	hnrayst an hour ago \| parent \| prev [-]
		Easiest is probably a local S3-compatible like MinIO (docker) and point Litestream at that endpoint. If you want hosted, R2/B2 free tiers work too. It only needs S3 creds + endpoint.

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vivzkestrel 5 days ago | parent | prev | next [-]

- anyone knows what is the equivalent of litestream for postgres? - i want to be able to pg_dump and barman my database to s3 by streaming it. is that possible?

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pbrumm 4 days ago | parent | next [-]

There is wal-g that moves the wal files to s3 and you can spin up any number of instances off of that. Works great for catching up secondary servers

	▲	vivzkestrel 4 days ago \| parent [-]
		just a quick look on it, is that more like pg_dump or barman?

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direwolf20 3 hours ago | parent | prev | next [-]

Did Postgres's WAL archiving feature not work for you?

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Eikon 3 hours ago | parent | prev [-]

You might be interested in ZeroFS [0], it works great with Postgres [1].

To achieve what you describe, you should be just able to setup a Postgres replica that’s setup on top of ZeroFS.

[0] https://github.com/Barre/ZeroFS

[1] https://github.com/Barre/ZeroFS?tab=readme-ov-file#postgresq...

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dang 2 hours ago | parent | prev [-]

[sorry for the weird timestamps - the OP was submitted a while ago and I just re-upped it and it hit a dumb bug which I haven't gotten around to fixing yet]