static int getSchemaVersion(InstanceConfig instanceConfig) {
    return getSchemaVersion(instanceConfig.getRecord());
  }
Get the schema version associated with the given instance (if any).
@param instanceConfig the {@link InstanceConfig} associated with the interested instance.
@return the schema version of the information stored. If the field is absent in the InstanceConfig, the version
        is assumed to be 0, and 0 is returned.
ambry-clustermap/src/main/java/com/github/ambry/clustermap/ClusterMapUtils.java