Creating Workflow

A workflow is a sequence of tasks necessary to complete a job. Tasks can be dependant on other tasks. Each task is defined as part of the workflow. A workflow can then be scheduled for execution by attaching a trigger to it. Multiple triggers can be attached to a workflow.

Creating a workflow in Kronos

Step 1: Create workflow

A workflow in Kronos is defined as:

KEY	DESCRIPTION	TYPE	DEFAULT	MANDATORY
name	name of the workflow	string	None	yes
namespace	namespace the workflow belongs to (used in multi-tenancy)	map	None	yes
description	a short description about workflow	map	None	no
tasks	list of tasks part of the workflow defined as workflow task(see below)	list	None	yes
properties	global properties available to each workflow task within the workflow. The task can refer to a property defined at a workflow level as ${workflow.prop_name} where prop_name is the name of the property defined at workflow level	map	None	no
emailOnSuccess	list of recipient to send email on success	list	None	no
emailOnFailure	list of recipient to send email on failure	list	None	no

Note: Email notifications will be sent only if mail service is configured while starting the scheduler. To configure mail service in scheduler check out configuring email notifications guide.

A workflow task in Kronos is defined as:

KEY	DESCRIPTION	TYPE	DEFAULT	MANDATORY
name	name of the task	string	None	yes
type	type of task (used to identify the task handler for executing the task)	string	None	yes
properties	properties required by the task handler to execute the task	map	None	no
dependsOn	list of tasks (name) current task depends on	list	None	no
maxExecutionTimeInMs	max allowed time for the task to finish execution in millisecond	long	86400	no
enabled	enable/ disable a task, disabled tasks won’t be picked for execution	boolean	true	no
policies	set of policies to apply on task completion. As of now only retry policy is supported.	policy	None	no

Note: If a task is marked as disabled (enabled=false), All the tasks depending on it should be explicitly marked as disabled otherwise the scheduler will throw a validation exception.

Workflow Task Properties

Workflow task properties can be set in 3 different ways in Kronos.

1. Fixed properties - A fixed key/value pair where key is a string and value can be any fixed value.
2. Workflow properties - A workflow task can refer to properties defined at a workflow level. The properties defined at workflow level can be referred as ${workflow.param_name} where param_name is the property key defined at the workflow level.
3. Properties from dependee task - A task can also refer to output variable of its dependee task or any of the task in its dependee hierarchy. For e.g. If task C depends on B and B depends on A. Task C can refer to property of A via ${A.keyName} or B via ${B.keyName}, where keyName is the output of task A or B.

Workflow Task Policy

As of now Kronos supports only retry policies at a task level which is applied on failure. A task will be retried on failure independent of the failure reason.

retry

KEY	DESCRIPTION	TYPE	DEFAULT	MANDATORY
type	type of policy (should be retry)	enum	None	yes
maxRetryCount	number of times to retry the task on failure	int	1	no

Step 2: Create a trigger for the workflow

A workflow trigger in Kronos is defined as:

KEY	DESCRIPTION	TYPE	DEFAULT	MANDATORY
name	name of the trigger	string	None	yes
workflow	name of the workflow to assign the trigger	string	None	yes
namespace	namespace the workflow trigger belongs to (used in multi-tenancy)	map	None	yes
startAt	time in millis to start the scheduling of workflow	long	None	no
schedule	defines the schedule (can be a cron/ simple/ fixed/ daily or calendar type)	schedule	None	yes
endAt	time in millis to stop the scheduling of workflow	long	None	no
enabled	enable/ disable a trigger, disabled trigger won’t schedule workflow for execution	boolean	true	no
properties	properties to be overridden defined at a workflow level before execution	map	None	no

Schedule

Kronos supports 5 type of schedule.

• simple - defines strict/literal interval-based schedules for workflow (can be compared directly with quartz simple schedule)
• cron - defines CronExpression based schedules for workflow (can be compared directly with quartz cron based schedule)
• calendar - defines calendar time (day, week, month, year) interval-based schedules for workflow (can be compared directly with quartz calendar interval schedule)
• daily_time - provide an extra convenient method for you to set the trigger's start time and end time of the day (can be compared directly with quartz daily time interval schedule)
• fixed - schedule workflow at a fixed delay, each execution is scheduled relative to the actual execution time of the previous execution of workflow.

simple

KEY	DESCRIPTION	TYPE	DEFAULT	MANDATORY
type	type of schedule (should be simple)	enum	None	yes
misfireInstruction	set the trigger mis fire instruction	int	0	no
repeatIntervalInMs	the interval at which the trigger should repeat in milliseconds	long	None	yes
repeatForever	specify that the trigger will repeat indefinitely	boolean	false	no
repeatCount	the number of time the trigger will repeat	int	None	no

reapeatCount takes precedence over repeatForever.

cron

KEY	DESCRIPTION	TYPE	DEFAULT	MANDATORY
type	type of schedule (should be cron)	enum	None	yes
misfireInstruction	set the trigger mis fire instruction	int	0	no
cronExpression	cron expression string to base the schedule on	string	None	yes
timezone	the time zone for which this CronExpression will be resolved	string	None	no

timezone should be either an abbreviation such as "PST", a full name such as "America/Los_Angeles", or a custom ID such as "GMT-8:00".

calendar

KEY	DESCRIPTION	TYPE	DEFAULT	MANDATORY
type	type of schedule (should be calendar)	enum	None	yes
misfireInstruction	set the trigger mis fire instruction	int	0	no
repeatInterval	the interval at which the trigger should repeat	long	1	no
repeatIntervalUnit	the time unit (IntervalUnit) of the interval	intervalunit	Day	no
preserveHourOfDayAcrossDaylightSavings	If intervals are a day or greater, this property (set to true) will cause the firing of the trigger to always occur at the same time of day,(the time of day of the startTime) regardless of daylight saving time transitions.	boolean	false	no
skipDayIfHourDoesNotExist	If intervals are a day or greater, and preserveHourOfDayAcrossDaylightSavings property is set to true, and thehour of the day does not exist on a given day for which the trigger would fire, the day will be skipped and the trigger advanced a secondinterval if this property is set to true.	boolean	false	no
timezone	the time zone for which this CronExpression will be resolved	string	None	no

timezone should be either an abbreviation such as "PST", a full name such as "America/Los_Angeles", or a custom ID such as "GMT-8:00".

Available values for repeatIntervalUnit are: MILLISECOND, SECOND, MINUTE, HOUR, DAY, WEEK, MONTH, YEAR

daily_time

KEY	DESCRIPTION	TYPE	DEFAULT	MANDATORY
type	type of schedule (should be daily_time)	enum	None	yes
misfireInstruction	set the trigger mis fire instruction	int	0	no
repeatInterval	the interval at which the trigger should repeat	long	1	no
repeatIntervalUnit	the time unit (IntervalUnit) of the interval	string	Minute	no
repeatCount	the number of time the trigger will repeat	int	-1	no
startTimeOfDay	set the trigger to begin firing each day at the given time	timeofday		no
endTimeOfDay	set the trigger to end firing each day at the given time	timeofday		no
daysOfWeek	set the trigger to fire on the given days of the week	set	[1,2,3,4,5,6,7]	no

startTimeOfDay is set to beginning of day (0:0:0) is not specified and endTimeofDay is set to end of the the day (23:59:59) if not specified by default.

daysOfWeek refer to set of days in a week where Sunday is 1 and Saturday is 7.

Available values for repeatIntervalUnit are: MILLISECOND, SECOND, MINUTE, HOUR, DAY, WEEK, MONTH, YEAR.

fixed

KEY	DESCRIPTION	TYPE	DEFAULT	MANDATORY
type	type of schedule (should be fixed)	enum	None	yes
intervalInMs	the interval in milliseconds at which the trigger should repeat from the previous execution	long	0	no

Sample workflows and triggers are available here for reference.