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https://github.com/OCA/report-print-send.git
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Use a cron instead of threads to update printers status
The implementation with threads was blocking the loading of the server in multiprocess. Using a cron will lower the frequency of the updates but at least it is simple and reliable. Fixes #14
This commit is contained in:
Guewen Baconnier
@@ -24,195 +24,14 @@
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import logging
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import os
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from contextlib import contextmanager
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from datetime import datetime
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from tempfile import mkstemp
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from threading import Thread
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import cups
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import psycopg2
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from openerp import models, fields, api, sql_db
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from openerp.tools import ormcache
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from openerp import models, fields, api
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_logger = logging.getLogger(__name__)
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POLL_INTERVAL = 15 # seconds
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class PrintingPrinterPolling(models.Model):
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""" Keep the last update time of printers update.
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This table will contain only 1 row, with the last time we checked
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the list of printers from cups.
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The table is locked before an update so 2 processes won't be able
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to do the update at the same time.
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"""
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_name = 'printing.printer.polling'
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_description = 'Printers Polling'
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last_update = fields.Datetime()
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@api.model
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def find_unique_record(self):
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polling = self.search([], limit=1)
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return polling
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@api.model
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@ormcache()
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def table_exists(self):
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return self._model._table_exist(self.env.cr)
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def _create_table(self, cr):
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super(PrintingPrinterPolling, self)._create_table(cr)
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self.clear_caches()
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@api.model
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def find_or_create_unique_record(self):
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polling = self.find_unique_record()
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if polling:
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return polling
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cr = self.env.cr
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try:
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# Will be released at the end of the transaction. Locks the
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# full table for insert/update because we must have only 1
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# record in this table, so we prevent 2 processes to create
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# each one one line at the same time.
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cr.execute("LOCK TABLE %s IN SHARE ROW EXCLUSIVE MODE NOWAIT" %
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self._table, log_exceptions=False)
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except psycopg2.OperationalError as err:
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# the lock could not be acquired, already running
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if err.pgcode == '55P03':
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_logger.debug('Another process/thread is already '
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'creating the polling record.')
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return self.browse()
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else:
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raise
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return self.create({'last_update': False})
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@api.multi
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def lock(self):
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""" Lock the polling record
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Lock the record in the database so we can prevent concurrent
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processes to update at the same time.
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The lock is released either on commit or rollback of the
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transaction.
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Returns if the record has been locked or not.
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"""
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self.ensure_one()
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cr = self.env.cr
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sql = ("SELECT id FROM %s WHERE id = %%s FOR UPDATE NOWAIT" %
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self._table)
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try:
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cr.execute(sql, (self.id, ), log_exceptions=False)
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except psycopg2.OperationalError as err:
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# the lock could not be acquired, already running
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if err.pgcode == '55P03':
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_logger.debug('Another process/thread is already '
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'updating the printers list.')
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return False
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if err.pgcode == '40001':
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_logger.debug('could not serialize access due to '
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'concurrent update')
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return False
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else:
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raise
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return True
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@contextmanager
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@api.model
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def start_update(self):
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locked = False
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polling = self.find_or_create_unique_record()
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if polling:
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if polling.lock():
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locked = True
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yield locked
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if locked:
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polling.write({'last_update': fields.Datetime.now()})
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@ormcache()
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def _last_update_cached(self):
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""" Get the last update's datetime, the returned value is cached """
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polling = self.find_unique_record()
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if not polling:
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return False
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last_update = polling.last_update
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if last_update:
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last_update = fields.Datetime.from_string(last_update)
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return last_update
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@api.model
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def last_update_cached(self):
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""" Returns the last update datetime from a cache
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The check if the list of printers needs to be refreshed is
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called very often (each time a browse is done on ``res.users``),
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so we avoid to hit the database on every updates by keeping the
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last value in cache.
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The cache has no expiration so we manually clear it when the
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poll interval (defaulted to 10 seconds) is reached.
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"""
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last_update = self._last_update_cached()
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now = datetime.now()
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if last_update and (now - last_update).seconds >= POLL_INTERVAL:
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# Invalidates last_update_cached and read a fresh value
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# from the database
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self.clear_caches()
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return self._last_update_cached()
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return last_update
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@api.model
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def need_update(self):
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last_update = self.last_update_cached()
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now = datetime.now()
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# Only update printer status if current status is more than 10
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# seconds old.
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if not last_update or (now - last_update).seconds >= POLL_INTERVAL:
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self.clear_caches() # invalidates last_update_cached
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return True
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return False
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@api.model
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def update_printers_status(self):
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cr = sql_db.db_connect(self.env.cr.dbname).cursor()
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uid, context = self.env.uid, self.env.context
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with api.Environment.manage():
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try:
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self.env = api.Environment(cr, uid, context)
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printer_obj = self.env['printing.printer']
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with self.start_update() as locked:
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if not locked:
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return # could not obtain lock
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printer_recs = printer_obj.search([])
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try:
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connection = cups.Connection()
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printers = connection.getPrinters()
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except:
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printer_recs.write({'status': 'server-error'})
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else:
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for printer in printer_recs:
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cups_printer = printers.get(printer.system_name)
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if cups_printer:
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printer.update_from_cups(connection,
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cups_printer)
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else:
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# not in cups list
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printer.status = 'unavailable'
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self.env.cr.commit()
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except:
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self.env.cr.rollback()
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raise
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finally:
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self.env.cr.close()
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class PrintingPrinter(models.Model):
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"""
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@@ -240,6 +59,24 @@ class PrintingPrinter(models.Model):
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location = fields.Char(readonly=True)
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uri = fields.Char(string='URI', readonly=True)
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@api.model
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def update_printers_status(self):
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printer_recs = self.search([])
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try:
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connection = cups.Connection()
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printers = connection.getPrinters()
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except:
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printer_recs.write({'status': 'server-error'})
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else:
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for printer in printer_recs:
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cups_printer = printers.get(printer.system_name)
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if cups_printer:
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printer.update_from_cups(connection, cups_printer)
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else:
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# not in cups list
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printer.status = 'unavailable'
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return True
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@api.multi
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def _prepare_update_from_cups(self, cups_connection, cups_printer):
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mapping = {
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@@ -299,40 +136,6 @@ class PrintingPrinter(models.Model):
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_logger.info("Printing job: '%s'" % file_name)
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return True
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@api.model
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def start_printer_update(self):
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polling_obj = self.env['printing.printer.polling']
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thread = Thread(target=polling_obj.update_printers_status, args=())
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thread.start()
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@api.model
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def update(self):
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"""Update printer status if current status is more than 10s old."""
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polling_obj = self.env['printing.printer.polling']
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if not polling_obj.table_exists():
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# On the installation of the module, this method could be
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# called before the 'printing.printer.polling' table exists
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# (but the model already is in memory)
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return
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if polling_obj.need_update():
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self.start_printer_update()
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return True
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@api.v7
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def browse(self, cr, uid, arg=None, context=None):
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_super = super(PrintingPrinter, self)
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recs = _super.browse(cr, uid, arg=arg, context=context)
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if not recs._context.get('skip_update'):
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recs.with_context(skip_update=True).update()
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return recs
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@api.v8
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def browse(self, arg=None):
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recs = super(PrintingPrinter, self).browse(arg=arg)
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if not recs._context.get('skip_update'):
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recs.with_context(skip_update=True).update()
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return recs
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@api.multi
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def set_default(self):
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if not self:
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@@ -1,6 +1,6 @@
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<?xml version="1.0"?>
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<openerp>
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<data>
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<data noupdate="1">
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<!-- printing.action -->
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<record model="printing.action" id="printing_action_1">
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<field name="name">Send to Printer</field>
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@@ -16,5 +16,19 @@
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<field name="fields_id" search="[('model','=','ir.actions.report.xml'),('name','=','property_printing_action')]"/>
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<field name="value" eval="'printing.action,'+str(printing_action_2)"/>
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</record>
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<record forcecreate="True" id="ir_cron_update_printers" model="ir.cron">
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<field name="name">Update Printers Status</field>
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<field eval="True" name="active"/>
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<field name="user_id" ref="base.user_root"/>
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<field name="interval_number">1</field>
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<field name="interval_type">minutes</field>
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<field name="numbercall">-1</field>
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<field eval="False" name="doall"/>
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<field eval="'printing.printer'" name="model"/>
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<field eval="'update_printers_status'" name="function"/>
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<field eval="'()'" name="args"/>
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</record>
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</data>
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</openerp>
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