Async cookie persistence

[Kludex]

Originally opened by @tomchristie on 2019-03-21 13:58:49 in encode/httpx

Some cookie stores will be on-disk. Writing to the cookie store will be a blocking operation. Really we ought to make sure that any write to an on-disk cookie jar is performed within a threadpool.

Starlette's run_in_threadpool may be useful.

Questions:

• Can we differentiate between in-memory and on-disk cases?
• What is the default?

[Kludex]

Originally posted by @tomchristie on 2019-03-27T16:18:14Z

The default is all just in memory. You can provide alternate cookie jar implementations that write to disk, but I think we can just treat this as a limitation at this point. If you're using a to-file cookie storage implementation, then that part of your code will be (file-write) blocking.