Class: OpenWFE::Scheduler

The Scheduler is used by OpenWFEru for registering ‘at’ and ‘cron’ jobs. ‘at’ jobs to execute once at a given point in time. ‘cron’ jobs execute a specified intervals. The two main methods are thus schedule_at() and schedule().

schedule_at() and schedule() await either a Schedulable instance and params (usually an array or nil), either a block, which is more in the Ruby way.

Examples

   scheduler.schedule_in("3d") do
       regenerate_monthly_report()
   end
       #
       # will call the regenerate_monthly_report method
       # in 3 days from now

    scheduler.schedule "0 22 * * 1-5" do
        log.info "activating security system..."
        activate_security_system()
    end

    job_id = scheduler.schedule_at "Sun Oct 07 14:24:01 +0900 2009" do
        init_self_destruction_sequence()
    end

an example that uses a Schedulable class :

   class Regenerator < Schedulable
       def trigger (frequency)
           self.send(frequency)
       end
       def monthly
           # ...
       end
       def yearly
           # ...
       end
   end

   regenerator = Regenerator.new

   scheduler.schedule_in("4d", regenerator)
       #
       # will regenerate the report in four days

   scheduler.schedule_in(
       "5d",
       { :schedulable => regenerator, :scope => :month })
           #
           # will regenerate the monthly report in 5 days

There is also schedule_every() :

    scheduler.schedule_every("1h20m") do
        regenerate_latest_report()
    end

The scheduler has a "exit_when_no_more_jobs" attribute. When set to ‘true’, the scheduler will exit as soon as there are no more jobs to run. Use with care though, if you create a scheduler, set this attribute to true and start the scheduler, the scheduler will immediately exit. This attribute is best used indirectly : the method join_until_no_more_jobs() wraps it.

The :scheduler_precision can be set when instantiating the scheduler.

    scheduler = OpenWFE::Scheduler.new(:scheduler_precision => 0.500)
    scheduler.start
        #
        # instatiates a scheduler that checks its jobs twice per second
        # (the default is 4 times per second (0.250))

Cron up to the second

Since OpenWFEru 0.9.16, a cron schedule can be set at the second level :

    scheduler.schedule "7 * * * * *" do
        puts "it's now the seventh second of the minute"
    end

The OpenWFEru scheduler recognizes an optional first column for second scheduling. This column can, like for the other columns, specify a value ("7"), a list of values ("7,8,9,27") or a range ("7-12").

Exceptions

The OpenWFEru scheduler will output a stacktrace to the STDOUT in case of exception. There are two ways to change that behaviour.

    # 1 - providing a lwarn method to the scheduler instance :

    class << scheduler
        def lwarn (&block)
            puts "oops, something wrong happened : "
            puts block.call
        end
    end

    # 2 - overriding the [protected] method log_exception(e) :

    class << scheduler
        def log_exception (e)
            puts "something wrong happened : "+e.to_s
        end
    end

‘Every jobs’ and rescheduling

Every jobs can reschedule/unschedule themselves. A reschedule example :

    schedule.schedule_every "5h" do |job_id, at, params|

        mails = $inbox.fetch_mails
        mails.each { |m| $inbox.mark_as_spam(m) if is_spam(m) }

        params[:every] = if mails.size > 100
            "1h" # lots of spam, check every hour
        else
            "5h" # normal schedule, every 5 hours
        end
    end

Unschedule example :

    schedule.schedule_every "10s" do |job_id, at, params|
        #
        # polls every 10 seconds until a mail arrives

        $mail = $inbox.fetch_last_mail

        params[:dont_reschedule] = true if $mail
    end

Attributes

precision	[RW]	By default, the precision is 0.250, with means the scheduler will check for jobs to execute 4 times per second.
stopped	[RW]	As its name implies.

Public Class methods

is_cron_string(s)

Returns true if the given string seems to be a cron string.

Examples

Tags

Cron up to the second

Exceptions

‘Every jobs’ and rescheduling

Methods

Attributes

Public Class methods

Public Instance methods