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Cluster Range Distribution Policy

A probe cluster is a logical container for a number of Data Flow Probes. When you define a network range for the cluster, the cluster distributes the overall set IP address ranges between the Probes in the cluster balancing the load between them.

A cluster balances its IP addresses among its Probes as follows:

  1. To ensure that specific IP addresses are always distributed to a particular Probe, you can set a TQL query constraint on that Probe. When the TQL query runs, the resulting IP addresses are distributed to the respective Probe.

  2. All of the remaining IP addresses in the cluster's range are then distributed evenly among all of the cluster's Probes (including the Probes with the TQL query constraints).

    Note The cluster balances its IP addresses over its Probes in such a way so as to minimize IP movement after the IP addresses have been distributed to the Probes.

    If the cluster's IP addresses become unbalanced, that is, one Probe is assigned a wider set of IP ranges than other Probes, the cluster tries to re-balance the IP addresses among its Probes. The cluster is allowed to retry to balance the Probes depending on how much IP movement is allowed. For details, see How to Limit IP Movement in a Cluster.



Consider the following scenario:

  • Cluster Range: -

  • Cluster includes Probe1, Probe2, Probe3

  • TQL constraint on Probe1: Probe1's range must include IP addresses -

After running a TQL query on UCMDB, the following IP addresses are returned:

The cluster balances its network ranges among its Probes as follows:

  • Because of the TQL constraint on Probe1, range - is specifically distributed to Probe1
  • Range - is out of the cluster's range, so it is not distributed to any of the cluster's Probes
  • The remaining IP addresses in the cluster's ranges are then evenly balanced among all of the cluster's Probes. The remaining ranges are:

    • -
    • -

    The cluster always attempts to distribute an IP address to a Probe whose TQL constraint includes that IP address

    Note Technically, IP addresses -, which fall within Probe1's TQL constraint, can be distributed to any of the cluster's Probes, and not necessarily only to Probe 1. This is because these addresses were not found by the TQL query, which means they do not exist in UCMDB. In turn, no actual workload can be distributed to them anyway, so it is insignificant which Probe received these IP addresses.

    Nonetheless, the cluster does make a special effort to distribute these IP addresses to Probe1. This way, if a subsequent recalculation of the TQL query returns these IP addresses, they are already in place, and IP movement is minimized.

    Furthermore, when the TQL query is recalculated, and if these addresses are found in UCMDB, these IP addresses are indeed distributed to Probe 1, per its TQL constraint.