Add package to support LiteFS in the WebSocket server #11
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tantaman
changed the title
These are not litefs specific
instead we'll re-route write at the top of the stack at the websocket handler.
We have more information at this level and cleanup is easier to manage as the connection over which to forward writes is per-db.
- introduce DBFactory so different backends can provide different DBs. E.g., LiteFS provides one that forwards writes - make certain db methods async given we now have async operations when forwarding writes
… initialization of cached items
- make litefs db - deal with missing reqid - report errors
…hokidar on ubunutu
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LiteFS is a bit more complicated when running WebSocket servers.
The reason is that all writes must go to the primary for LiteFS. In our websocket server, we determine if the received message is a write. If so, we send it on to the primary.
This isn't quite enough though. WebSocket servers are stateful by nature and we need to keep this state maintained on the edge node responsible for the websocket connection and not build up state on the primary that the writes are forwarded to.
In other words:
So after forwarding a write the follower will (for certain writes) await completion of that write (by following the -pos txid) and update its internal state.
LiteFS technically supports write forwarding (superfly/litefs#56) but the way it works is by passing the write lock around and is not recommended for cases with high write volume.