Admin Interface

autocron comes with a command line tool to inspect the content of the database and to manage the settings:

$ autocron
usage: autocron command line tool [-h] [-i]
[--set-max-workers MAX_WORKERS]
[--set-autocron-lock AUTOCRON_LOCK]
[--set-monitor-lock MONITOR_LOCK]
[--set-blocking-mode BLOCKING_MODE]
[--set-worker-idle-time WORKER_IDLE_TIME]
[--set-monitor-idle-time MONITOR_IDLE_TIME]
[--set-result-ttl RESULT_TTL]
[--set-defaults] [--delete-database]
database

database:

Name of the database to work on, required.

--delete-database:

deletes the selected database.

-h:

show the help menu

-i:

views the current the settings, number of aktive workers and their corresponding pids in case autocron is running.

--set-defaults:

set the database to the default settings.

--set-autocron-lock:

set the lock flag of autocron. If the flag is set, autocron is disabled and will not start. Accepts the case-insensitive arguments on, off, true, false. on and true are setting the flag (disable autocron), off and false delete the flag. Default to False (autocron enabled).

--set-max-workers:

set number of maximum worker processes at next start of autocron. Takes an integer as argument (autocron will start this number of workers and not “as up to”). A useful number of workers depends on the application. Normalwise it makes no sense to start more workers than the number of available cpu-cores. Defaults to 1.

--set-monitor-idle-time:

set the idle time (integer in seconds) of the monitor thread supervising the workers. Default value is 5 seconds. Normalwise there is no need to change this setting.

--set-monitor-lock:

set monitor lock flag. This is an internal flag indicating that a monitor process is active. When autocron starts with multiple processes of the web-application in parallel, the first process will start the monitor and the worker processes. Setting the flag prevents other processes to do the same and start additonal workers on their own. On shutdown, this flag gets released. However the admin tool allows to set the flag if something does not work as it should. Arguments are on, off, true, false. During normal operation you should never have the need to deal with this setting.

--set-blocking-mode:

set the blocking mode flag. Task registering is a blocking operation because of database access. If this flag is False task registration is handled by a separate thread in a non-blocking way. If this is not desired, i.e. by django in debug mode with an active reloader, setting this flag to True will suppress the start of a registration thread. Default setting is False.

--set-worker-idle-time:

set the idle time (integer in seconds) for the worker processes. If no tasks on due the worker(s) will sleep for the given time before checking again for new tasks. Defaults to 0 seconds, what means that the value is auto-calculated. This is a setting for fine-tuning and normalwise there is no need to change this.

--set-result-ttl:

set the result time-to-life (ttl, in seconds). Stored results are deleted after this timespan. A change of this value will applied to new results. Already stored results keep the previous assigned ttl. Defauts to 1800 seconds (30 minutes).

Settings

autocron comes with default settings. The admin interface allows to change settings. By default autocron starts with one (1) worker process. When no tasks are on due the worker sleeps for one (1) second. When waking up the worker selects the next tasks on due for processing. After handling the task the worker looks for a another task on due that may have been registered meanwhile. If no tasks have been registered the worker goes into idle mode again. The duration of the idle-time can be set with the option --set-worker-idle-time.

If the worker-idle-time is set to zero (0) (which is the default), the idle-time is calculated depending on the number of workers. The idle-time starts with one (1) second and is slightly increased on more than eight (8) workers to reduce the probability that all workers access the database at the same time and may have to wait because of locks. This should work for most cases.

Adding more workers to handle tasks is useful if tasks are permanently registered in a faster pace than the current number of workers can handle them. There is no upper limit for the number of workers (beside the system resources), but normalwise it makes no sense to start more workers than the number of available cpu-cores.

autocron can get deactivated with the --set-autocron-lock setting. This can be useful for debugging. The default value is False. Set the value to True or on to deactivate autocron (the arguments are case insensitive). Even when autocron.start() is called in the code, autocron will check the flag and will not start. The delay decorator will behave the same, returning a Result instance but the task itself will get executed in sync, i.e. a blocking task will block. Same if the --blocking-mode flag is set: task registration will be in sync with the application. This can be useful during development of django-applications.

Database Storage

All settings are stored in the autocron database. The default location for the databases is in the ~.autocron/ directory. When autocron starts and can not find the database, a new database is created with the default settings.

On shutting down the application, all unhandled tasks keep persistent in the autocron database and will get handled the next time the application starts. If the database file gets deleted, the contents are lost. Otherwise it is safe to delete the databases – next time when the application starts, autocron will create a fresh one.