MM2 nodes only communicate via Kafka -- no connection is required between them.
To reconfigure, a rolling restart probably won't do what you expect, since the configuration is always dictated by a single leader. Once the leader is bounced, it will broadcast the new configuration via Kafka. If you bounce a follower, it will still use the old configuration. It's slightly more complicated than that actually, since there are multiple connectors in each cluster->cluster "herder". When there are multiple clusters being replicated, there may be dozens of leaders. So a rolling restart might be a good idea for larger deployments. And technically there are some properties that do affect followers, e.g. a follower will read connection info like bootstrap.servers directly from mm2.properties, not from the leader via Kafka. Obviously that would be a chicken-egg problem otherwise! So a rolling restart would be prudent when making such changes. So I guess, generally speaking, rolling restarts are a good idea -- just be advised that it won't necessarily behave as you expect. Ryanne On Thu, Jan 16, 2020, 7:55 AM Péter Sinóros-Szabó <peter.sinoros-sz...@transferwise.com.invalid> wrote: > Hi, > > I run two instances of MM2 with the command connect-mirror-maker.sh > > Q1., Is there any requirement to cluster MM2? Like a network connection > between the nodes? How do MM2 coordinate the work between nodes? > > Q2., Assuming I run two instances and want to update the configuration, > should it work if I rolling restart the nodes after each other? It seems > that after the restart both nodes still run with the old configuration. So > what should be the correct way of reconfiguring a MM2 cluster? > > Cheers, > Peter >
