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Load balancing in Autosys
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job(n) Tnm Tcl Extension job(n) __________________________________________________________________________________________________________________________________________________ NAME
job - Invoke Tcl procedures at regular intervals. _________________________________________________________________ DESCRIPTION
The job command provides a convenient mechanism to implement Tcl procedures that are invoked at regular intervals. Jobs are activated from the Tcl event loop. Every job can have arbitrary attributes to store job specific state information between two invocations. These attributes help to avoid global variables in order to keep the Tcl name-space clean. The job scheduler itself relies heavily on the Tcl timer interface which itself depends on the system clock. Moving the system clock back- wards can have the effect that jobs are not activated for the amount of time the system clock was moved backwards. Similarly, moving the system clock forward can have the effect that jobs are activated earlier for the amount of time the system clock was moved forward. JOB COMMAND
The job command allows to create new jobs and to wait for jobs to complete. The job command can also be used to retrieve status information from the job scheduler. job create [option value ...] The job create command creates a new job object. The options can be used to configure the behaviour of the new job. See the config- ure command below for the details. job current The job current command returns the name of the currently running job. An empty string is returned if no job is running. job info The job info command returns a list of all job names. The list will be empty if there are no jobs known in this Tcl interpreter. job schedule The job schedule command invoke the scheduler. This is usually done automatically from the event loop. This command may be used dur- ing long computations since the scheduler is not preemptive. Note, this command can cause arbitrary side effects and should be used with care. job wait The job wait command blocks until all existing jobs have been finished. The command will wait infinitely if there is at least one job left. Events are processed while waiting for the jobs to finish which can have arbitrary side effects. JOB INSTANCE COMMAND
Every job is represented by a job object command which allows to manipulate the job. job# attribute [name [value]] The job# attribute command allows to save job specific data in job attributes. If called without any arguments, all existing attribute names for this job will be returned. If called with a name argument, the current value of the attribute will be returned. Non-existing attributes do not produce an error. Instead, an empty string is returned. Calling the option with a name and a value causes the value to be saved in the job attribute. job# cget option The job# cget command returns the current value of a configuration option. See the description of supported options below. job# configure [option value ...] The job# configure command manipulates configuration options. See the description of supported options below. A list describing all current options is returns if the options argument is missing. job# destroy The job# destroy command destroys the job object. This command forces the object to change into the expired state. The scheduler will cleanup this object the next time it is active. job# wait The job# wait command blocks and processes events until the current job changes into the expired state. JOB OPTIONS
Every job has associated configuration options which control when a job is activated and which Tcl command is bound to the job. -command command The -command option defines the Tcl command that is evaluated whenever the job is activated. -interval time The -interval option defines the time interval between two job activations in milliseconds. -iterations number The -iterations option defines the total number of times that a job is activated. If this value reaches 0, the job will change its state to expired. Note, if the iterations options is never used, it will also have the value 0 but nothing special happens to the job object. -status state The -status option provides access to the current job state. A job is always in one of the states waiting, suspended, running and expired. A job in the expired state will be removed from the system once the scheduler gets activated again. Suspended jobs are not activated by the job scheduler. A suspended job can be resumed by changing its state to running. -time time The -time option returns the number of milliseconds until this job is activated the next time. This option is read-only. SEE ALSO
scotty(1), Tnm(n), Tcl(n) AUTHORS
Juergen Schoenwaelder <schoenw@cs.utwente.nl> Tnm job(n)
