Uploaded image for project: 'ZooKeeper'
  1. ZooKeeper
  2. ZOOKEEPER-1506

Re-try DNS hostname -> IP resolution if node connection fails

    XMLWordPrintableJSON

Details

    • Improvement
    • Status: Resolved
    • Blocker
    • Resolution: Fixed
    • 3.4.5, 3.4.6
    • 3.4.7, 3.5.0, 3.6.0
    • server
    • Ubuntu 11.04 64-bit

    • Hide
      Tests pass with this patch.
      This patch is for the branch-3.4 branch ONLY.
      Show
      Tests pass with this patch. This patch is for the branch-3.4 branch ONLY.

    Description

      In our zoo.cfg we use hostnames to identify the ZK servers that are part of an ensemble. These hostnames are configured with a low (<= 60s) TTL and the IP address they map to can and does change. Our procedure for replacing/upgrading a ZK node is to boot an entirely new instance and remap the hostname to the new instance's IP address. Our expectation is that when the original ZK node is terminated/shutdown, the remaining nodes in the ensemble would reconnect to the new instance.

      However, what we are noticing is that the remaining ZK nodes do not attempt to re-resolve the hostname->IP mapping for the new server. Once the original ZK node is terminated, the existing servers continue to attempt contacting it at the old IP address. It would be great if the ZK servers could try to re-resolve the hostname when attempting to connect to a lost ZK server, instead of caching the lookup indefinitely. Currently we must do a rolling restart of the ZK ensemble after swapping a node – which at three nodes means we periodically lose quorum.

      The exact method we are following is to boot new instances in EC2 and attach one, of a set of three, Elastic IP address. External to EC2 this IP address remains the same and maps to whatever instance it is attached to. Internal to EC2, the elastic IP hostname has a TTL of about 45-60 seconds and is remapped to the internal (10.x.y.z) address of the instance it is attached to. Therefore, in our case we would like ZK to pickup the new 10.x.y.z address that the elastic IP hostname gets mapped to and reconnect appropriately.

      Attachments

        1. zk-dns-caching-refresh.patch
          7 kB
          Michael Lasevich
        2. Zookeeper-1506.patch
          40 kB
          Robert P. Thille
        3. ZOOKEEPER-1506.patch
          35 kB
          Robert P. Thille
        4. ZOOKEEPER-1506.patch
          35 kB
          Robert P. Thille
        5. ZOOKEEPER-1506.patch
          36 kB
          Robert P. Thille
        6. ZOOKEEPER-1506.patch
          39 kB
          Robert P. Thille
        7. ZOOKEEPER-1506.patch
          5 kB
          Michi Mutsuzaki
        8. ZOOKEEPER-1506.patch
          7 kB
          Michi Mutsuzaki
        9. ZOOKEEPER-1506.patch
          6 kB
          Michi Mutsuzaki
        10. ZOOKEEPER-1506.patch
          6 kB
          Michi Mutsuzaki
        11. ZOOKEEPER-1506.patch
          3 kB
          Michi Mutsuzaki
        12. ZOOKEEPER-1506.patch
          3 kB
          Michi Mutsuzaki
        13. ZOOKEEPER-1506.patch
          2 kB
          Michi Mutsuzaki
        14. ZOOKEEPER-1506-fix.patch
          0.7 kB
          Michi Mutsuzaki

        Issue Links

          Activity

            People

              rthille Robert P. Thille
              mheffner Mike Heffner
              Votes:
              29 Vote for this issue
              Watchers:
              45 Start watching this issue

              Dates

                Created:
                Updated:
                Resolved: