Swarm deadlock

The goal of this repository is to help debugging an issue in Swarm where one node hangs in the awaiting_sync_ack state.

Please note not all executions will result in a deadlock.

Steps to reproduce

docker-compose build repro_{2,1,3}
docker-compose up repro_{2,1,3}

Expected result

You should see one node in the awaiting_sync_ack state and the other two nodes in the tracking state. This situation can be identified by the following line in the docker output:

Swarm.Tracker state: awaiting_sync_ack

You should also see the following warning:

[tracker:handle_cast] unrecognized cast: {:sync_recv, #PID<16218.180.0>, {{0, {0, 1}}, 0}, []}