Nirvana Scheduling : Conditional Triggers

Conditional triggers execute tasks when specific conditions occur. Each defined trigger has a number of attributes that can be used as part of the trigger expression and evaluated to determine whether the tasks are executed. For basic information on the grammar for conditional triggers, please read the section on conditional triggers in the writing scripts help file. The conditional triggers are signified by using the 'when' keyword. The expression entered after the keyword represent the trigger object(s) and the values to be checked against.

This section will describe in detail the triggers that are available and how to use them within a trigger expression :

• Trigger Expressions
• Store Triggers
• Interface Triggers
• Memory Triggers
• Realm Triggers
• Cluster Triggers
• Counter Triggers
• Timer Triggers
• Config Triggers

To view examples of scheduling scripts, please click here.

Trigger Expressions

A trigger expression is constructed from the definition of the trigger object(s) to be evaluated and the values that will be used in the comparison. The trigger used in the expression can be either the actual trigger object, or the declared name of the trigger from the declarations section of the script. Multiple triggers can be used in the expression using conditional operators (AND | OR).

For example, the following expression can be used to evaluate when a Realm's Interface accept threads are exhausted 5 times. When this happens, the accept threads will be increased by 10. This schedule will continually monitor the state of the interface and self-manage the accept threads so the realm server is always able to accept connections from clients.

scheduler realmInterfaceSchedule {

declare Interface myNHP ("nhp0");
declare Counter myCounter("myExhaustedThreads");

when (myNHP.idleThreads == 0) {

Logger.report("NHP0 Interface has no idles Threads");
myCounter.inc();

}

when (myCounter >= 5) {

Logger.report("Increasing the accept thread count on NHP0");
myNHP.threads("+10");
myCounter.reset();

}

}

The above schedule will monitor the number of times the accept threads are exhausted and when the counter trigger hits 5 times, the number of threads will be increased by 10.

The next section will describe the available trigger objects and the available triggers on those objects that can be used within

Trigger Objects Table

Store Triggers - Channel / Queue based triggers

Store triggers are declared using the following syntax as an example:

declare Store myChannel("/customer/sales");

The table below lists those triggers that can be evaluated on a Store object, such that the trigger expression will look like :

when (myChannel.connections > 100) {

}

Interface Triggers - Nirvana Interface based triggers

Interface triggers are declared using the following syntax as an example:

declare Interface myNHP("nhp0");

The table below lists those triggers that can be evaluated on an Interface object, such that the trigger expression will look like :

when (myNHP.connections > 100) {

}

MemoryManager Triggers - Nirvana JVM Memory Management based triggers

MemoryManager triggers are declared using the following syntax as an example:

declare MemoryManager mem;

The table below lists those triggers that can be evaluated on the memory management object, such that the trigger expression will look like :

when (mem.freeMemory < 1000000) {

}

Realm Triggers - Nirvana Realm based triggers

Realm triggers are declared using the following syntax as an example:

declare Realm myRealm("productionmaster");

The table below lists those triggers that can be evaluated on the realm object, such that the trigger expression will look like :

when (realm.connections > 1000) {

}

Cluster Triggers - Nirvana Cluster based triggers

Cluster triggers are declared using the following syntax as an example, assuming a cluster is made up of 4 realms:

declare Cluster myNode1("realm1");
declare Cluster myNode2("realm2");
declare Cluster myNode3("realm3");
declare Cluster myNode4("realm4");

The table below lists those triggers that can be evaluated on the cluster object, such that the trigger expression will look like :

when ( Cluster.isOnline("realm1") == true ){

}

Counter Triggers - Counter value based triggers

Counter triggers allow you to keep a local count of events occurring with the Nirvana scheduler engine. The values of the Counters can be incremented decremented and reset within the tasks section of a trigger declaration. Counter triggers are declared using the following syntax as an example:

declare Counter counter1 ("myCounter");

The counter trigger can be evaluated by referencing the Counter object itself, such that the trigger expression will look like :

when ( counter1 > 5) {

}

Timer Triggers - Timer based triggers

Timer triggers allow you to start a timer that will keep track of how long (in seconds) it has been running and then evaluate the running time within a trigger expression. Time triggers are declared using the following syntax as an example:

declare Timer reportTimer ("myTimer");

The timer trigger can be evaluated by referencing the timer object itself, such that the trigger expression will look like :

when ( reportTimer == 60 ) {

}

Config Triggers -Nirvana configuration triggers

Config triggers refer to any of the configuration values available in the Config panel for a realm. Any configuration value can be used as part of a trigger expression. Config triggers are declared using the following syntax as an example (below example refers to the 'GlobalValues' configuration group:

declare Config myGlobal ("GlobalValues");

The table below lists those triggers that can be evaluated on a Config object, such that the task expression will look like :

when (myGlobal.MaxNoOfConnections == -1) {

}