Scheduler

Scheduler is a service that schedules timers to perform actions at a later time or in a repeating fashion. It is important to use scheduler over built in methods like setTimeout and setInterval for efficiency. Scheduler operates by saving timers to a SQL database. This database is checked at an interval specified in the config. During this check, all the timers that have reached their expiration have their functionality executed.

Timers can be created, deleted and modified in three ways. The first way is manually through the Leverege UI, under the timers section. The second way is to start a timer message in the Leverege Platform. There are several of these messages and they can be found in detail in the Messages library. The last way to interact with Timers is through the api routes exposed by scheduler.

Timers have two main attributes, the first attribute is focused on when the timers will run. Timers can be set to occur once, at a set interval or on a cron schedule. The second attribute determines what action will be taken. Actions can be to publish a message to a topic, trigger a script or query a url.

Configuration

All configuration options for scheduler have defaults set, but important information to set up a SQL connection is included that will almost always require reconfiguring.

Optional

Name	Description	Default
TRANSPORT_CONFIG	config for readers and writers	{ type, host, port }
NSQ_HOST_ADDR	host address for NSQ, if TRANSPORT_CONFIG is not specified	'127.0.0.1'
NSQ_HOST_PORT	port for NSQ, if TRANSPORT_CONFIG is not specified	4150
SCHEDULER_TOPIC	topic that scheduler will listen to for incoming messages	'scheduler'
PORT	port that scheduler will listen to	9937
CORS_ORIGIN	acceptable CORS origin	'*'
POLL_EVERY	time interval in ms that scheduler will check all timers	2000
SCHEDULER_BATCH_SIZE	size of the batches that will be processed	1000
SCHEDULER_LOOK_AHEAD	ms that will be added to check if timers have passed	250
SQL_MAX_CONNECTIONS	max number of SQL connections	1
SQL_HOST	SQL host	'localhost'
SQL_PORT	SQL port	3306
SQL_USER	SQL user	'root'
SQL_PASSWORD	SQL password	'root'
SQL_DB	SQL database	'scheduler'
SQL_TABLE	SQL table	'scheduler'
RESCHEDULER_BATCH_SIZE	size of batches when timers are rescheduled	100
SQL_CA	SQL ssl ca	undefined
SQL_CLIENT_CERT	SQL ssl cert	undefined
SQL_CLIENT_KEY	SQL ssl key	undefined