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From "Robert Metzger (JIRA)" <j...@apache.org>
Subject [jira] [Created] (FLINK-2967) TM address detection might not always detect the right interface on slow networks / overloaded JMs
Date Wed, 04 Nov 2015 13:21:27 GMT
Robert Metzger created FLINK-2967:

             Summary: TM address detection might not always detect the right interface on
slow networks / overloaded JMs
                 Key: FLINK-2967
                 URL: https://issues.apache.org/jira/browse/FLINK-2967
             Project: Flink
          Issue Type: Bug
    Affects Versions: 0.9, 0.10, 1.0
            Reporter: Robert Metzger
            Assignee: Robert Metzger

I'm talking to a user which is facing the following issue:
Some of the TaskManagers select the wrong IP address out of the available network interfaces.

The first address we try to connect to is the one returned by {{InetAddress.getLocalHost()}}.
This address is the right IP address to use, but the JobManager is not able to respond within
the timeout (50ms) to that connection request.
So the TM tries the next address, which is not publicly reachable. However, the TM can connect
to the JM from there. Netty will later fail to connect to the TM from the other TMs.

There are two solutions for this issue:
- Allow users to configure a higher timeout for the first address detection strategy. In most
cases, the address returned by {{InetAddress.getLocalHost()}} is correct. By setting a high
timeout, users with slow networks / overloaded JMs can make sure the TM picks this address
- add an Akka message which we send from the TM to the JM, and the JM tries to connect to
the TM. If that succeeds, we know that the TM is reachable from the outside.
The problem is that we have to start a separate actor system on the TaskManager first. We
have to do this because might use a wrong ip address for the TM (so we might end up starting
actor systems until we found an externally reachable ip)

I'm first going to implement the first approach. If that solution works well for my user,
I'll contribute this to 0.10 / 1.0.
If not, I'll implement the second approach.

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