In-memory database (cache) preloading event. Preload event happens every time there is a change
in grid topology, which means that a node has either joined or left the grid.
Grid events are used for notification about what happens within the grid. Note that by
design GridGain keeps all events generated on the local node locally and it provides
APIs for performing a distributed queries across multiple nodes:
-
GridEvents#remoteQuery(GridPredicate,long,int...) -
asynchronously querying events occurred on the nodes specified, including remote nodes.
-
GridEvents#localQuery(GridPredicate,int...) -
querying only local events stored on this local node.
-
GridEvents#localListen(GridPredicate,int...) -
listening to local grid events (events from remote nodes not included).
User can also wait for events using method
GridEvents#waitForLocal(GridPredicate,int...).
Events and Performance
Note that by default all events in GridGain are enabled and therefore generated and stored
by whatever event storage SPI is configured. GridGain can and often does generate thousands events per seconds
under the load and therefore it creates a significant additional load on the system. If these events are
not needed by the application this load is unnecessary and leads to significant performance degradation.
It is highly recommended to enable only those events that your application logic requires
by using
GridConfiguration#getIncludeEventTypes() method in GridGain configuration. Note that certain
events are required for GridGain's internal operations and such events will still be generated but not stored by
event storage SPI if they are disabled in GridGain configuration.