Comment 2 for bug 1583683

When agents start, they are always in an "upgrading" state so as to not attempt operations while an upgrade is occurring. Once the check that an upgrade is not required, they will switch out of that state.

It looks like in your case that that check isn't happening because of the mongo errors. There is a tool that you can use to purge these missing transactions: https://github.com/mjs/mgopurge

You can build and run it yourself, or let me know if you'd like me to build it for you.

Once you run mgopurge, try and restart the jujud agent on machine 0. If that was the only problem, the agent should come back up and exit the upgrading state.