[IMP] cron: comments and docstrings.
bzr revid: vmt@openerp.com-20110808130502-htps768jts63m9sx
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@ -162,7 +162,7 @@ class ir_cron(osv.osv):
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if numbercall:
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# Reschedule our own main cron thread if necessary.
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# This is really needed if this job run longer that its rescheduling period.
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# This is really needed if this job runs longer than its rescheduling period.
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print ">>> advance at", nextcall
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nextcall = time.mktime(nextcall.timetuple())
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openerp.cron.schedule_in_advance(nextcall, cr.dbname)
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@ -28,6 +28,12 @@ cron jobs, for all databases of a single OpenERP server instance.
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It defines a single master thread that will spawn (a bounded number of)
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threads to process individual cron jobs.
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The thread runs forever, checking every 60 seconds for new
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'database wake-ups'. It maintains a heapq of database wake-ups. At each
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wake-up, it will call ir_cron._run_jobs() for the given database. _run_jobs
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will check the jobs defined in the ir_cron table and spawn accordingly threads
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to process them.
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"""
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import heapq
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@ -37,64 +43,61 @@ import time
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import openerp
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""" Singleton that keeps track of cancellable tasks to run at a given
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timestamp.
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The tasks are characterised by:
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* a timestamp
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* the database on which the task run
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* a boolean attribute specifying if the task is canceled
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Implementation details:
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- Tasks are stored as list, allowing the cancellation by setting
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the boolean to True.
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- A heapq is used to store tasks, so we don't need to sort
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tasks ourself.
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"""
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# Heapq of database wake-ups. Note that 'database wake-up' meaning is in
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# the context of the cron management. This is not about loading a database
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# or otherwise making anything about it.
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_wakeups = [] # TODO protect this variable with a lock?
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# Each element is a triple (timestamp, database-name, boolean). The boolean
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# specifies if the wake-up is canceled (so a wake-up can be canceled without
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# relying on the heapq implementation detail; no need to remove the job from
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# the heapq).
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_wakeups = []
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# Mapping of database names to the wake-up defined in the heapq,
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# so that we can cancel the wake-up without messing with the heapq
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# internal structure.
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# internal structure: lookup the wake-up by database-name, then set
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# its third element to True.
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_wakeup_by_db = {}
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_logger = logging.getLogger('cron')
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# Re-entrant lock to protect the above _wakeups and _wakeup_by_db variables.
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# We could use a simple (non-reentrant) lock if the runner function below
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# was more fine-grained, but we are fine with the loop owning the lock
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# while spawning a few threads.
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_wakeups_lock = threading.RLock()
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# Maximum number of threads allowed to process cron jobs concurrently.
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_thread_count = 2 # TODO make it configurable
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# A (non re-entrant) lock to protect the above _thread_count variable.
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_thread_count_lock = threading.Lock()
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# Maximum number of threads allowed to process cron jobs concurrently.
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_thread_count = 2
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_logger = logging.getLogger('cron')
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def get_thread_count():
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""" Return the number of available threads. """
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return _thread_count
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def inc_thread_count():
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""" Increment by the number of available threads. """
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global _thread_count
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with _thread_count_lock:
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_thread_count += 1
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def dec_thread_count():
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""" Decrement by the number of available threads. """
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global _thread_count
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with _thread_count_lock:
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_thread_count -= 1
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def cancel(db_name):
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""" Cancel the next wake-up of a given database, if any. """
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""" Cancel the next wake-up of a given database, if any.
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:param db_name: database name for which the wake-up is canceled.
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"""
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_logger.debug("Cancel next wake-up for database '%s'.", db_name)
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with _wakeups_lock:
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if db_name in _wakeup_by_db:
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@ -111,16 +114,20 @@ def cancel_all():
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def schedule_in_advance(timestamp, db_name):
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""" Schedule a wake-up for a new database.
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""" Schedule a new wake-up for a database.
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If an earlier wake-up is already defined, the new wake-up is discarded.
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If another wake-up is defined, it is discarded.
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If another wake-up is defined, that wake-up is discarded and the new one
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is scheduled.
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:param db_name: database name for which a new wake-up is scheduled.
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:param timestamp: when the wake-up is scheduled.
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"""
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if not timestamp:
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return
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with _wakeups_lock:
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# Cancel the previous wakeup if any.
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# Cancel the previous wake-up if any.
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add_wakeup = False
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if db_name in _wakeup_by_db:
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task = _wakeup_by_db[db_name]
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@ -152,6 +159,7 @@ def runner():
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registry['ir.cron']._run_jobs()
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amount = 60
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with _wakeups_lock:
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# Sleep less than 60s if the next known wake-up will happen before.
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if _wakeups and get_thread_count():
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amount = min(60, _wakeups[0][0] - time.time())
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time.sleep(amount)
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