Add a method of specifying multiple upstream hosts in a Network store

[chrisjbray]

A small extension to NetworkStore to allow SMC-like multiple upstreams, but specified as a space-delimited list in the config file.

scribed will connect to one of the upstreams and continue to use it until it fails, then reconnect to a different one and backfill from the secondary store automatically.

[mdordal]

You can do iter->find() here, which is probably clearer.

[mdordal]

Also, more generally, what did you do to test this?

[chrisjbray]

As for testing, I just built it and ran it, saw that it connected to a random machine each time I started scribed, I used a slightly modified scribecat to tail a file to it, confirmed it was passing traffic, then killed the scribed on the upstream machine, saw that scribed reconnected to a different upstream, repeated a few times then left it tailing for ~12 hours. As far as I can tell no ill effects.

[mdordal]

It might be clearer if though if loadFromList took an out parameter like network_config::getService does above.

[chrisjbray]

I agree, changed to out parameters like the getService

[anton-povarov]

this doesn't work when you only have default store, because NetworkStore::copy() never copes serviceList member.
fix:

• store->serviceList = serviceList;