Scheduling Grammar
The grammar for scheduling scripts is extremely simple
to understand. The script must conform to a predefined
structure and include elements that map to the grammar
expected by the Realm Server Scheduler Engine.
In its simplest form the Nirvana scheduler syntax starts
with the command 'scheduler'. This tells the
parser that a new scheduler task is being defined. This
is followed by the name of the scheduler being defined,
this is a user defined name. For example:
scheduler myScheduler {
}
Within this structure, triggers and tasks are defined.
A task is the actual operation the server will perform,
and it can be executed at a certain time or frequency,
or when a condition occurs. Within the scheduler context
the following verbs can be used to define tasks to be
executed.
declare : Used to define the name
of a trigger for later user.
initialise : Is the first thing run
when a scheduler is started (also run when the realm
server starts up).
every : Used to define a time/calendar
based event.
when : Used to define a conditional
trigger and the list of tasks to execute when it fires.
else : Used after a conditional trigger
that will fire if the condition evaluates to false
The following shows the basic grammar and structure
of a scheduling script.
/*
Comment block
*/
scheduler <User defined Name>
{
declare <TRIGGER_DECLARATION>+
initialise {
<TASK_DECLARATION>+
}
/*
Time based tasks
*/
every <TIME_EXPRESSION> {
<TASK_DECLARATION>+
}
when ( <TRIGGER_EXPRESSION>
) {
<TASK_DECLARATION>+
} else {
<TASK_DECLARATION>+
}
where :
TRIGGER_DECLARATION ::= <TRIGGER>
<NAME> (<TRIGGER_ARGUMENT_LIST>)
TRIGGER ::= Valid trigger, for more
info on valid triggers click here
TRIGGER_ARGUMENT_LIST ::= Valid comma
separated list of arguments for the trigger
TASK_DECLARATION ::= Valid task,
for more information on valid tasks, please click
here
TRIGGER_EXPRESSION ::=
<TRIGGER_EXPRESSION> <LOGICAL_OPERATOR>
<TRIGGER_EXPRESSION> |
<TRIGGER> |
<NAME> <COMPARISION_OPERATOR> <VALUE>
TIME_EXPRESSION ::=
<HOURLY_EXPRESSION> |
<DAILY_EXPRESSION> |
<WEEKLY_EXPRESSION> |
<MONTHLY_EXPRESSION> |
<YEARLY_EXPRESSION>
HOURLY_EXPRESSION ::= <MINUTES>
DAILY_EXPRESSION ::= <HOUR>
<COLON> <MINUTES>
WEEKLY_EXPRESSION ::= <DAYS_OF_WEEK>
<SPACE> <HOUR> <COLON> <MINUTES>
MONTHLY_EXPRESSION ::= <DAY_OF_MONTH>
<SPACE> <HOUR> <COLON> <MINUTES>
YEARLY_EXPRESSION ::= <DAY_OF_MONTH>
<HYPHEN> <MONTH> <SPACE> <HOUR>
<COLON> <MINUTES>
MINUTES ::= Minutes past
the hour, i.e. a value between 00 and 59
HOUR ::= Hour of the day, i.e. a value between
00 and 23
DAYS_OF_WEEK ::=
<DAY_OF_WEEK> |
<DAY_OF_WEEK> <SPACE> <DAY_OF_WEEK>
DAY_OF_WEEK ::= Mo | Tu | We |
Th | Fr | Sa | Su
DAY_OF_MONTH ::= Specific
day of the month to perform a task, i.e. a value between
01 and 28
MONTH ::= The month of the year,
JAN, FEB, MAR etc.
NAME ::= The variable name for a trigger
COMPARISION_OPERATOR ::= > | =>
| < | <= | == | !=
LOGICAL_OPERATOR ::= AND | OR
COLON ::= The ":"
character
SPACE ::= The space character
HYPHEN ::= The "-"
character
+ ::=
indicates that this can occur multiple times
VALUE ::= Any valid string or numeric
value.
Declarations
The declarations section of the script defines any
triggers and assigns them to local variable names. The
grammar notation defined above specifies that the declaration
section of a schedule script can contain multiple declarations
of triggers. For example, the following declarations
section would be valid based on the defined grammar:
declare Config myGlobalConfig
("GlobalValues");
declare Config myAuditConfig ( "AuditSettings");
declare Config myTransConfig ( "TransactionManager");
The above declarations define 3 variables that refer
to the the Config trigger. The declared objects can
be used in a time based trigger declaration, conditional
triggers and to perform tasks on.
Initialise
The initialise section of the schedule script defines
what tasks are executed straight away by the server
when the script is deployed. These initial tasks are
also executed every time the Realm Server is started.
An example of a valid initialise section of a schedule
script is shown below:
initialise {
Logger.report("Realm optimisation script and
monitor startup initialising");
myAuditConfig.ChannelACL("false");
myAuditConfig.ChannelFailure("false");
myGlobalConfig.MaxBufferSize(2000000);
myGlobalConfig.StatusBroadcast(2000);
myGlobalConfig.StatusUpdateTime(86400000);
myTransConfig.MaxTransactionTime(3600000);
Logger.setlevel(4);
}
The example above ensures that each time a server starts,
the tasks declared are executed. Using the variables
defined in the declarations section, as well as the
Logger task, the server will always ensure that the
correct configuration values are set on the server whenever
it starts.
Every Clause
The every clause defines those tasks that are executed
at specific times and frequencies as defined in the
grammar above. Tasks can be executed every hour at a
specific time pas the hour, every day at a certain time,
every week on one or more days at specific times or
day, every month on a specific day of the month and
a specific day of the year.
The grammar above defines how to declare an every clause.
Based on this grammar the following examples demonstrate
how to declare when to perform tasks :
Hourly Example (Every half past
the hour, log a message to the realm server log)
every 30 {
Logger.report("Hourly - Excecuting Tasks");
}
Daily Example (Every day at 18:00,
perform maintenance on the customerSales
channel )
every 18:00 {
Logger.report("Daily - performing maintenance");
Store.maintain("/customer/sales");
}
Weekly Example (Every week, on sunday
at 17:30, purge the customer sales channel)
every Su 17:30 {
Logger.report("Weekly - Performing Purge");
Store.purge("/customer/sales");
}
Monthly Example (Every 1st of the
month, at 21:00, stop all interfaces and start them
again)
every 01 21:00 {
Logger.report("Monthly - Stopping interfaces
and restarting");
Interface.stopAll();
Interface.startAll();
}
Yearly Example (Every 1st of the
January, at 00:00, stop all interfaces and start them
again)
every 01-Jan 00:00 {
Logger.report("Yearly - Stopping interfaces
and restarting");
Interface.stopAll();
Interface.startAll();
}
When Clause
The when clause defines a trigger that evaluates a
specific value and executes a task if the evaluation
result is 'true'. The grammar for the when clause is
defined above. The following example shows a valid when
clause :
when (MemoryManager.FreeMemory
< 30000000) {
Logger.report("Memory below 30M, performing
some clean up");
FlushMemory(true);
}
The above example will trigger the Realm Server JVM
to call garbage collection when the amount of free memory
drops to below 30MB.
Else Clause
The else clause defines an alternative action to the
when clause if the when clause evaluates to 'false'.
The grammar for the else clause is defined above. The
following example shows a valid when clause :
when (MemoryManager.FreeMemory
< 30000000) {
Logger.report("Memory below 30M, performing
some clean up");
FlushMemory(true);
} else {
Logger.report("Memory not below 30M, no
clean up required");
}
The above example will trigger the Realm Server JVM
to call garbage collection when the amount of free memory
drops to below 30MB.
To view a sample scheduling script, please click here. |
