[Proposal] Feat/circuit interop

[dryajov]

adding priorities for transports

Related PR:
libp2p/js-libp2p-switch#217

[daviddias]

@dryajov Can you explain what you are trying to achieve with priorities? This is more than what relay should try to achieve. I don't see a necessity for it right now.

[dryajov]

@diasdavid

The basic requirement is to be able to dial on certain transports before others.

Right now, when dialing happens, all the transports are tried in sequence in whatever order they happened to be returned by the const tKeys = swarm.availableTransports(pi). I want to be able to push a transport (i.e. Circuit) to be tried last, or after some other transports have been tried. The priority property would allow for this as I'm sorting the transports based on it, in the availableTransports method.

The requirement for circuit (and I might be a bit off on this one) is to be able to dial on circuit addresses only if all else failed. In this case, I'm setting all transports to a priority of 1 and Circuit to 100. This allows me to push it to the end of the list of available transports.

IMHO, this is a useful feature to have.

[dryajov]

@diasdavid Alternatively or in addition to this, we could also allow priority be controlled from the config as well, so that we can choose which transports are preferred based on environment conditions.

[daviddias]

Going to skip this, for now.