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.