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 HOSTNAME & PORT 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:
- Change the hostname or the port or both.
- Restart the application node.
- 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.