Is it ok to point the Docker host OS to the Rancher DNS server?

Rancher 1.x
1

Hi,

I have an ELK stack running within Rancher and I want to send Docker container (also managed by rancher) logs using the Docker log drivers. I configured logstash to receive syslog events and exposed a port in the ELK container. On the container, where I want to send the logs from, I configured the syslog-address=tcp://host:port and enabled it.

Now the issue I have is that the ELK stack hostname is not available from the Docker host OS because the logging driver is not aware of the container internal dns server.

I created a workaround by pointing the Docker host OS namespace server to 169.254.169.250 and then use ElkStack_elk_1 as syslog-address…

Is it ok and safe to do so or is there an alternative and better approach to achieve this?

Regards,

Geert

2

Any thoughts on this question?

3

This doesn’t seem like a great idea, though it sounds like it mostly works for you. I could see issues like something wanting DNS answers before the container is up on a reboot…

4

Ok thx Vincent. Do you know which DNS server is used by the internal Rancher DNS to resolve external domains?

5

Whatever is configured in Docker, which defaults to what is configured on the host, or Google (8.8.8.8/8.8.4.4).

6

Ok, this could explain some UnknownHostExceptions. The host is configured to use the internal Rancher DNS server. Which probably means that I am into some kind of loop when resolving domain names… :slight_smile:

I think I need to find another solution…