our session records sometimes grow to unreasonable sizes

[Trolldemorted]

My libsignal.db is now above 200MB. I think that it is unlikely, but we may have a bug in libsignal-protocol-dotnet.

[Trolldemorted]

I have been having a look at my database, it seems like I have way too many ReceiverChains in several sessions. The maximum number should be 5, the session with my girlfriend's phone has got more than 7000.

@golf1052 what was this todo for? So far i haven't the faintest idea why there are old chains lingering around.

[golf1052]

No idea, I hadn't needed to touch that file. That TODO was from one of the older maintainers.

[Trolldemorted]

It is indeed a libsignal-protocol issue:

libsignal-protocol-java is updating an element in the list with

this.sessionStructure = this.sessionStructure.toBuilder()
                                             .setReceiverChains(chainAndIndex.second(), updatedChain)
                                             .build();

so it obviously replaces the element at chainAndIndex.second() with updatedChain.

libisgnal-protocol-dotnet is using

this.sessionStructure.ReceiverChains.Insert((int)chainAndIndex.second(), chain);

which inserts chain at chainAndIndex.second(), but it also shifts all elements beyond the index to the right.

This explains the db size and the degrading performance as the sessions age.

[Trolldemorted]

Looks like signal-csharp/libsignal-protocol-dotnet@4456cc1 and signal-csharp/libsignal-protocol-dotnet@d2635df solved this.

Shall we roll a new version out? The impact on our message processing speed was huge.