Troubleshooting Mesos DNS

How can I check the Mesos-DNS version?

You can check the Mesos-DNS version with mesos-dns -version.

NOTE: The HTTP interface only resolves hostnames in the Mesos domain. We do not recommend upgrading Mesos-DNS independently of DC/OS. Use the version of Mesos-DNS that shipped with your version of DC/OS.

What if Mesos-DNS fails to launch?

Check that port 53 and port 8123 are available and not in use by other processes.

What if my Agent nodes cannot connect to Mesos-DNS?

  • Make sure that port 53 is not blocked by a firewall rule on your cluster.

  • It is possible that the Master nodes are not running. Run sudo systemctl status dcos-mesos-dns and sudo journalctl -u dcos-gen-resolvconf.service -n 200 -f for more information about Mesos-DNS errors.

How do I configure my DC/OS cluster to communicate with external hosts and services?

For DNS requests for hostnames or services outside the DC/OS cluster, Mesos-DNS will query an external nameserver. By default, Google’s nameserver with IP address will be used. If you need to configure a custom external name server, use the resolvers parameter when you first install DC/OS.

IMPORTANT: External nameservers can only be set when you install DC/OS. They cannot be changed after installation.

What is the difference between leader.mesos and master.mesos?

To query the leading master node, always query leader.mesos. If you try to connect to master.mesos using HTTP, you will be automatically redirected to the leading master node.

However, if you try to query or connect to master.mesos using any method other than HTTP, the results will be unpredictable because the name will resolve to a random master node. For example, a service that attempts to register with master.mesos may communicate with a non-leading master node and will be unable to register as a service on the cluster.