DNS Resolution

The Telepresence DNS resolver is dynamically configured to resolve names using the namespaces of currently active intercepts. Processes running locally on the desktop will have network access to all services in the such namespaces by service-name only.

All intercepts contribute to the DNS resolver, even those that do not use the --namespace=<value> option. This is because --namespace default is implied, and in this context, default is treated just like any other namespace.

No namespaces are used by the DNS resolver (not even default) when no intercepts are active, which means that no service is available by <svc-name> only. Without an active intercept, the namespace qualified DNS name must be used (in the form <svc-name>.<namespace>).

See this demonstrated below, using the quick start's sample app services.

No intercepts are currently running, we'll connect to the cluster and list the services that can be intercepted.

$ telepresence connect
  
  Connecting to traffic manager...
  Connected to context default (https://<cluster-public-IP>)
  
$ telepresence list
  
  verylargejavaservice : ready to intercept (traffic-agent not yet installed)
  dataprocessingservice: ready to intercept (traffic-agent not yet installed)
  verylargedatastore   : ready to intercept (traffic-agent not yet installed)
  
$ curl verylargejavaservice:8080
  
  curl: (6) Could not resolve host: verylargejavaservice

This is expected as Telepresence cannot reach the service yet by short name without an active intercept in that namespace.

$ curl verylargejavaservice.default:8080
  
  <!DOCTYPE HTML>
  <html>
  <head>
      <title>Welcome to the EdgyCorp WebApp</title>
  ...

Using the namespaced qualified DNS name though does work.
Now we'll start an intercept against another service in the same namespace. Remember, --namespace default is implied since it is not specified.

$ telepresence intercept dataprocessingservice --port 3000
  
  Using deployment dataprocessingservice
  intercepted
      Intercept name: dataprocessingservice
      State         : ACTIVE
      Destination   : 127.0.0.1:3000
      Intercepting  : all TCP connections
  
$ curl verylargejavaservice:8080
  <!DOCTYPE HTML>
  <html>
  <head>
      <title>Welcome to the EdgyCorp WebApp</title>
  ...

Now curling that service by its short name works and will as long as the intercept is active.

The DNS resolver will always be able to resolve services using <service-name>.<namespace> regardless of intercepts.

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DNS Resolution

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