[BUG] Duplicate resource error when two servers are connected to each other

[MariemBaccari]

Description (Actual behavior)

When two Go backends are connected to each other (double connection), the client receives a "duplicate resource" when creating a meeting or a roll call.

Expected behavior

The client should be able to create the event.

How to reproduce

1. Create two server configs where both are on each other's list of servers
2. Run the servers and create a lao
3. Try to create a meeting
4. Notice that you will get a duplicate resource error (although the event is created)

Front-ends:

• Fe1-Web (please include browser's names & version)
• Fe2-Android (please specify if phone or emulation, and Android version)
• Not applicable

Back-ends:

• Be1-Go
• Be2-Scala
• Not applicable

Workaround

You can simply create one direction per pair of servers instead of having both servers in each other's list of "other-servers" in the config.

Possible root cause

On the Go backend, there is no mechanism for dropping a connection when a peer that's already connected tries to connect again which leads to "double connections". After some investigating, I found out that the server adds the same peer twice in the greet lao message which leads the client to create two connections for the same server. The client then sends the same message twice to the same server. One of them is processed properly and the other one is rejected so it sends a duplicate resource error back to the client.