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Where to View the Node ID


The Node ID is visible in the stats.do page of a ServiceNow instance node. It is the highlighted value in the following figure.

About Node IDs


A few pointers about the Node ID:

  • Every application node of an instance should have a unique Node ID.
  • The Node ID is generated by combination of HOSTNAMEPORT as an md5sum
    • md5sum calculates and verifies 128-bit MD5 hashes as described in RFC 1321. The MD5 hash functions as a compact digital fingerprint.
    • i.e.  the Node ID of an application node with hostname = 'localhost' and port 16000 will always be "97f69143118d564e464c5d4d4a74e4b8". This is easily verifiable by running the following command in a terminal:
      $ echo -n "localhost:16000" | md5
      97f69143118d564e464c5d4d4a74e4b8
  • The Node ID is generated every time at the startup of an application node.
  • Table [sys_cluster_state] stores the Node ID along with other node information.
  • The Node ID is NOT kept in the glide.properties file on the application node.
  • In case of a different Node ID, the system creates new entries in the sys_cluster_state table.
  • The Node ID can be same for any two application nodes only if they:
    • Have the same name
    • Are running on the same port
  • Do not have the same Node ID for two or more application nodes of an instance.
  • Same Node IDs can cause upgrade failures and incorrect data in [sys_cluster_state] and System Diagnostics.
  • A Node ID can be changed on demand:
    1. Change the hostname or the port or both.
    2. Restart the application node.
    3. Remove the old record from [sys_cluster_state].
  • Do not run self-hosted instances with an application host bounded to the loopback(localhost). This will create the same Node ID if their app nodes connect on the same port as well.

 

Article Information

Last Updated:2018-06-12 05:29:27
Published:2018-06-12
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