Troubleshoot Docker Trusted Registry

Estimated reading time: 2 minutes

High availability in DTR depends on having overlay networking working in UCP. To manually test that overlay networking is working in UCP run the following commands on two different UCP machines.

docker run -it --rm --net dtr-ol --name overlay-test1 --entrypoint sh docker/dtr
docker run -it --rm --net dtr-ol --name overlay-test2 --entrypoint ping docker/dtr -c 3 overlay-test1

You can create new overlay network for this test with docker network create -d overaly network-name. You can also use any images that contain sh and ping for this test.

If the second command succeeds, overlay networking is working.

DTR doesn’t come up after a Docker restart

This is a known issue with Docker restart policies when DTR is running on the same machine as a UCP controller. If this happens, you can simply restart the DTR replica from the UCP UI under “Applications”. The best workaround right now is to not run DTR on the same node as a UCP controller.

Etcd refuses to start after a Docker restart

If you see the following log message in etcd’s logs after a DTR restart it means that your DTR replicas are on machines that don’t have their clocks synchronized. Etcd requires synchronized clocks to function correctly.

2016-04-27 17:56:34.086748 W | rafthttp: the clock difference against peer aa4fdaf4c562342d is too high [8.484795885s > 1s]

Accessing the RethinkDB Admin UI

Warning: This command will expose your database to the internet with no authentication. Use with caution.

Run this on the UCP node that has a DTR replica with the given replica id:

docker run --rm -it --net dtr-br -p 9999:8080 svendowideit/ambassador dtr-rethinkdb-$REPLICA_ID 8080

Options to make this more secure:

  • Use -p to expose the admin UI only to localhost
  • Use an SSH tunnel in combination with exposing the port only to localhost
  • Use a firewall to limit which IPs are allowed to connect
  • Use a second proxy with TLS and basic auth to provide secure access over the Internet

Accessing etcd directly

You can execute etcd commands on a UCP node hosting a DTR replica using etcdctl via the following docker command:

docker run --rm -v dtr-ca-$REPLICA_ID:/ca --net dtr-br -it --entrypoint /etcdctl docker/dtr-etcd:v2.2.4 --endpoint https://dtr-etcd-$REPLICA_ID.dtr-br:2379 --ca-file /ca/etcd/cert.pem --key-file /ca/etcd-client/key.pem --cert-file /ca/etcd-client/cert.pem
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