The format of the outbound group session struct has changed. We nowadays correctly rotate the group session if we can't restore it, but it's still good to avoid logging the error in this case.
The SQLite crypto store uses rmp_serde to serialize all the data we're
going to store. This works nicely for most things, one exception to this
is the OutboundGroupSession type.
The OutboundGroupSession type stores to-device requests to ensure that
the session doesn't get used before it is shared with the whole group
and to ensure that the to-device requests get restored if the
session gets restored after an application restart.
The to-device requests type critically contain `Raw<AnyToDeviceEvent>`,
the `Raw` type here being the serde_json::Raw type. rmp_serde seems to
serialize this just fine, but later deserialization fails.
We're avoiding the issue by using serde_json to serialize the
OutboundGroupSession.
This makes it easier to implement it. However, using a different error
type than CryptoStoreError is a non-trivial change, so left for the
coming commits for all stores except the memory store.
Note about "Write-Ahead Log" (WAL) mode: The SQLite WAL mode has a
bunch of advantages that are quite nice to have:
1. WAL is significantly faster in most scenarios.
2. WAL provides more concurrency as readers do not block writers and a
writer does not block readers. Reading and writing can proceed
concurrently.
3. Disk I/O operations tends to be more sequential using WAL.
4. WAL uses many fewer fsync() operations and is thus less vulnerable
to problems on systems where the fsync() system call is broken.
The downsides of WAL mode don't really affect us. So let's turn it on.
More info: https://www.sqlite.org/wal.html
Co-authored-by: Jonas Platte <jplatte@matrix.org>
Co-authored-by: Damir Jelić <poljar@termina.org.uk>
