Since partitions are activated in different application
servers, PMI data for all partitions are possibly spread in different
application servers in a cluster. Most likely, the N most active partitions
in the whole cluster are of the most interest. The partitioning facility
(WPF) provides a PMI aggregation and sorting feature to satisfy this
requirement.
WPF elects one server as the PMI aggregator, which aggregates the
partition statistics data from all servers. The PMI aggregator is
an HA group with one of N policy. The policy name is called the WPF
PMI aggregator policy. You can customize the policy using the
wpfadmin tool.
At any time, there is only one PMI aggregator active in the core group.
This aggregator is responsible for aggregating the statistics for
all the partitioned applications. The best practice is to let this
PMI aggregator run on a separate server from those housing partitions
so it will not slow down business execution. Each application server
is responsible for publishing all of its partition PMI data when PMI
is turned on. The aggregator will run at a user-specified interval,
thus cutting down the volume of statistics the user will be shown.
The PMI aggregator will do the following:
- Aggregate the statistics from different servers for each partition.
Since partitions can be moved from one server to another, the PMI
data for a partition can be spread over different application servers.
The PMI aggregator must gather all the PMI data for a partition from
all servers.
- Sort the PMI statistics based on what users want. For example,
if users are interested in the most active (biggest number of transaction
counts) 50 partitions over last 15 seconds. The PMI aggregator will
calculate the PMI statistics from the last 15 seconds and sort them
based on the transaction count.
- Publish the sorted PMI statistics results.
Users can specify the statistics interests when they subscribe
the partitioning facility PMI statistics. These interests include
application name and session EJB name, statistics type, statistics
range, partition count, and aggregation interval. They can also changes
these interest after they subscribe them.