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Scheduler

Scheduler Overview

The scheduler microservice provides an internal clock, which can start operations in any Edge Xpert service.

The scheduler microservice calls an Edge Xpert service API URL using REST at a specified time, known as an interval, to trigger an operation, known as an interval action. For example, the scheduler microservice periodically calls the core data API to clean up old events that have been exported.

Scheduler uses a REST API. For further information on the support scheduler API, see Edge Xpert API

Note

In Edge Xpert v2, the REST API provided by the Scheduler has changed to use Data Transfer Objects (DTOs) for all responses and for all POST/PUT/PULL requests. All query APIs (GET) which return multiple objects, such as /all. provide offset and limit query parameters.

Default Interval Actions

The following interval actions are configured by default:

  • Clean up core data events that have been persisted for an extended period. Such events are removed to prevent the edge node from running out of space. This is the "ScrubAged" operation. The scheduler parameters determine how often and where to call in core data to invoke the clean up.

Note

The removal of stale records occurs on a configurable schedule. By default, the default action is invoked once a day at midnight.

Scheduler Persistance

The intervals and interval actions are persisted in the database. Persistence is accomplished by the Scheduler DB located in the current configured database.

Info

By default, Redis DB is used to persist all the scheduler service information including intervals and interval actions.

ISO 8601 Standard

The times and frequencies defined in the scheduler service's intervals are specified using the international date/time standard - ISO 8061. So, for example, the start of an inteval would be represented in YYYYMMDD'T'HHmmss format. 20180101T000000 represents January 1, 2018 at midnight. Frequencies are represented with ISO 8601 durations.

Scheduler Data Model

The following diagram shows the scheduler data model:

Scheduler Data Model

Data Dictionary

Property Description
An object defining a specific "period" in time
Id Uniquely identifies an interval, for example a UUID
Created A timestamp indicating when the interval was created in the database
Modified A timestamp indicating when the interval was last modified
Name the name of the given interval - unique for the EdgeX instance
Start The start time of the given interval in ISO 8601 format
End The end time of the given interval in ISO 8601 format
Interval How often the specific resource needs to be polled. It represents as a duration string. The format of this field is to be an unsigned integer followed by a unit which may be "ns", "us" (or "ยตs"), "ms", "s", "m", "h" representing nanoseconds, microseconds, milliseconds, seconds, minutes or hours. Eg, "100ms", "24h"
Property Description
The action triggered by the service when the associated interval occurs
Id Uniquely identifies an interval action, for example a UUID
Created A timestamp indicating when the interval action was created in the database
Modified A timestamp indicating when the interval action was last modified
Name the name of the interval action
Interval associated interval that defines when the action occurs
AdminState interval action state - either LOCKED or UNLOCKED
Protocol Indicates which protocol should be used. Only http is used today
Host The host targeted by the action when it activates
Port The port on the targeted host
Method Indicates which Http verb should be used for the REST endpoint.(Only using when type is REST
Path The HTTP path at the targeted host for fulfillment of the action.(Only using when type is REST)
Target The service target which is to receive the REST call - example core-data

See Interval and IntervalAction for more information.

Scheduler High Level Interaction diagram

The following high-level interaction diagram shows the scheduler interval actions in cleaning up old and exported (pushed) records from core data:

Scheduler Data Model

Scheduler Configuration Properties

The following table shows the Scheduler configuration properties:

Property Default Value Description
ScheduleIntervalTime 500 the time, in milliseconds, to trigger any applicable interval actions
Property Default Value Description
Default intervals for use with default interval actions
Name midnight Name of the every day at midnight interval
Start 20180101T000000 Indicates the start time for the midnight interval which is a midnight, Jan 1, 2018 which effectively sets the start time as of right now since this is in the past
Interval 24h defines a frequency of every 24 hours
Property Default Value Description
Configuration of the core data clean old events operation which is to kick off every midnight
Name scrub-aged-events name of the interval action
Host localhost run the request on core data assumed to be on the localhost
Port 59880 run the request against the default core data port
Protocol http Make a RESTful request to core data
Method DELETE Make a RESTful delete operation request to core data
Target core-data target core data
Path /api/v2/event/age/604800000000000 request core data's remove old events API with parameter of 7 days
Interval midnight run the operation every midnight as specified by the configuration defined interval
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