After restarting Gerrit all repositories are scheduled for replication. It apparently takes five hours to go through all of them. We should speed it up, maybe by adding more worked threads to each remotes?
Replication plugin documentation: https://gerrit.wikimedia.org/r/plugins/replication/Documentation/config.md
View after a restart at 8:15 today from https://grafana.wikimedia.org/d/RFLS1GsWk/replication-upstream