WebSphere® eXtreme Scale uses
an internal statistics model to track and filter data, which is the
underlying structure that all data views use to gather snapshots of
statistics.
Overview
Statistics in
WebSphere eXtreme Scale are tracked and contained
within StatsModules components. Within the statistics model, several
types of statistics modules exist:
- OGStatsModule
- Provides statistics for an ObjectGrid instance, including transaction
response times.
- MapStatsModule
- Provides statistics for a single map, including the number of
entries and hit rate.
- QueryStatsModule
- Provides statistics for queries, including plan creation and run
times.
- AgentStatsModule
- Provides statistics for DataGrid API agents, including serialization
times and run times.
- HashIndexStatsModule
- Provides statistics for HashIndex query and maintenance run times.
- SessionStatsModule
- Provides statistics for the HTTP session manager plug-in.
For details about the statistics modules, see the
Statistics API.
Statistics in a local environment
The model
is organized like an n-ary tree (a tree structure with the same degree
for all nodes) comprised of all of the StatsModule types mentioned
in the previous list. Because of this organization structure, every
node in the tree is represented by the StatsFact interface.
The StatsFact interface can represent an individual
module or a group of modules for aggregation purposes. For example,
if several leaf nodes in the tree represent particular MapStatsModule
objects, the parent StatsFact node to these nodes contains aggregated
statistics for all of the children modules. After you fetch a StatsFact
object, you can then use interface to retrieve the corresponding StatsModule.
Much like a tree map, you use a corresponding path or key
to retrieve a specific StatsFact. The path is a String[] value that
consists of every node that is along the path to the requested fact.
For example, you created an ObjectGrid called ObjectGridA, which contains
two Maps: MapA and MapB. The path to the StatsModule for MapA would
look like [ObjectGridA, MapA]. The path to
the aggregated statistics for both maps would be: [ObjectGridA].
Statistics in a distributed environment
In
a distributed environment, the statistics modules are retrieved using
a different path. Because a server can contain multiple partitions,
the statistics tree needs to track the partition to which each module
belongs. As a result, the path to look up a particular StatsFact object
is different. Using the previous example, but adding in that the maps
exist within partition 1, the path is [1, ObjectGridA,
MapA] for retrieving that StatsFact object for MapA.