Daemonising Celery and Flower on Windows¶
To ensure that the Celery task queue and Flower are started at system start-up it is advisable to launch them using batch files and configure Windows Task Scheduler to run each of these at system start-up.
Celery will sometimes fall over during the execution of a long task. If Celery frequently falls over on your system then Windows Task Scheduler can be used to restart Celery on a regular basis. The Task Scheduler can also be used to ensure celery is running a few minutes prior to scheduled PACS queries.
An example batch file is shown below for running and restarting Celery. This calls separate batch files to start Celery and Flower, also shown below.
Celery control batch file¶
celery_task.bat, to be run as a scheduled task.
:: Create variables containing the name and path of the Celery pid file and the :: names and paths to the batch files used to run Celery and Flower. SET celeryPidFile=E:\media_root\celery\default.pid SET celeryStartFile=D:\Server_Apps\celery\celery_start.bat SET flowerStartFile=D:\Server_Apps\flower\flower_start.bat :: Celery 3.1.25 cannot be shutdown gracefully, and has to be killed. The :: following command will kill all celery.exe processes and any python.exe :: processes associated with Celery. The celery.exe process that is running :: Flower will also be killed by this command. TASKKILL /IM celery.exe /T /F :: Force the deletion of the Celery pid file so that Celery can be restarted. DEL /F "%celeryPidFile%" :: Start Flower again. START /B CMD /C CALL "%flowerStartFile%" :: Start Celery again. START /B CMD /C CALL "%celeryStartFile%"
Celery start batch file¶
celery_start.bat, called by celery_task.bat.
:: Create variables containing the drive and path to OpenREM and the name and :: path of the Celery pid and log files. SET openremDrive=D: SET openremPath=D:\Server_Apps\python27\Lib\site-packages\openrem SET celeryPidFile=E:\media_root\celery\default.pid SET celeryLogFile=E:\media_root\celery\default.log :: Change to the drive on which OpenREM is installed and navigate to the :: OpenREM folder. %openremDrive% CD "%openremPath%" :: Start Celery. celery worker -n default -Ofair -A openremproject -c 4 -Q default --pidfile=%celeryPidFile% --logfile=%celeryLogFile%
Flower start batch file¶
flower_start.bat, called by celery_task.bat and also used to start Flower at system start-up.
:: Create variables containing the drive and path to OpenREM and the name and :: path of the Flower log file and the Flower port. SET openremDrive=D: SET openremPath=D:\Server_Apps\python27\Lib\site-packages\openrem SET flowerLogFile=E:\media_root\celery\flower.log SET flowerPort=5555 :: Change to the drive on which OpenREM is installed and navigate to the :: OpenREM folder. %openremDrive% CD "%openremPath%" :: Start Flower using Celery. celery -A openremproject flower --port="%flowerPort%" --loglevel=info --log-file-prefix="%flowerLogFile%"
Setting up a scheduled task¶
Task Scheduler on the OpenREM server and then click on the
Task Scheduler Library
item in the left-hand pane. This should look something like figure 1 below, but without the
OpenREM tasks present.
To create a new task for celery click on
Create Task... in the
Actions menu in the
right-hand pane. Give the task a name and description. Next, click on the
Change User or Group button and type
system in to the box, then click
Check Names, then click
OK. This sets the server’s
SYSTEM user to run the
task. Also check the
Run with highest prilileges box. Your task should now look similar
to figure 2.
Next, click on the
Triggers tab so that you can set when the task will be run. As a
minimum you should add an
At startup trigger. To do this, click
New.... In the
dialogue box that appears select
At startup from the
Begin the task options and ensure
Enabled checkbox is selected. Then click
OK. You may wish to add other
triggers that take place at specific times during the day, as shown in figure 3.
In the example shown in figure 3 celery is started at system start up, and restarted multiple times each day to ensure that it is running before any PACS queries. Your requirements may be more straightforward than this example.
Now click on the
Actions tab so that you can add the action that is taken when
the task is run. Click on
New..., and in the dialogue box that appears select
Start a program as the
Action. Click on
Browse and select the celery
batch file that you created earlier. Click
OK to close the
dialogue box. Figure 4 shows an example of the the
There are no particular conditions set for the task, as shown in figure 5.
Finally, click on the
Settings tab (figure 6). Check the
Allow task to be run on demand
box, and also the
If the running task does not end when requested, force it to stop box.
Stop the existing instance from the
If the task is already running, then the following rule applies:
list. Then click the
OK button to add the task to the scheduler library.
Repeat the above steps for the Flower batch file, but only configure the Flower task to trigger on system start-up: there should be no need to schedule re-starts of Flower.