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= Overview

:description: Scheduling in Helidon SE
:keywords: helidon, se, scheduling
:h1Prefix: SE
:feature-name: Scheduling
:rootdir: {docdir}/..

include::{rootdir}/includes/se.adoc[]

== Contents

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== Overview

Scheduling is an essential feature for the Enterprise. Helidon has its own implementation of Scheduling functionality
based on https://github.com/jmrozanec/cron-utils[Cron-utils].

include::{rootdir}/includes/dependencies.adoc[]

[source,xml]
----

    io.helidon.scheduling
    helidon-scheduling

----

== Usage
For scheduling periodic tasks, it is possible to choose a fixed rate or a Cron expression.

=== Fixed rate

[source,java]
.Scheduling with fixed rate use `Scheduling.fixedRate()` builder.
----
include::{sourcedir}/se/SchedulingSnippets.java[tag=snippet_1, indent=0]
----

Metadata like human-readable interval description or configured values are available through
FixedRateInvocation provided as task parameter.

[source,java]
.Invocation metadata
----
include::{sourcedir}/se/SchedulingSnippets.java[tag=snippet_2, indent=0]
----

include::{rootdir}/config/io_helidon_scheduling_FixedRate.adoc[tag=config,leveloffset=+2]

=== Cron

For more complicated interval definition, Cron expression can be leveraged with
`Scheduling.cron()` builder.

[source,java]
.Scheduling with Cron expression
----
include::{sourcedir}/se/SchedulingSnippets.java[tag=snippet_3, indent=0]
----

include::{rootdir}/config/io_helidon_scheduling_Cron.adoc[tag=config,leveloffset=+2]

=== Cron expression syntax

Cron expressions should be configured as follows.

include::{rootdir}/includes/cron.adoc[lines=19..]

Metadata like human-readable interval description or configured values are available through
CronInvocation provided as task parameter.

== Configuration
Scheduling is configurable with xref:../se/config/introduction.adoc[Helidon Config].

[source,java]
.Example of configuring
----
include::{sourcedir}/se/SchedulingSnippets.java[tag=snippet_4, indent=0]
----


== Examples

=== Fixed rate
For simple fixed rate invocation use .

[source,java]
.Example of scheduling with fixed rate use `Scheduling.fixedRate()` builder.
----
include::{sourcedir}/se/SchedulingSnippets.java[tag=snippet_5, indent=0]
----

Metadata like human-readable interval description or configured values are available through
`FixedRateInvocation` provided as task parameter.


[source,java]
.Example with invocation metadata
----
include::{sourcedir}/se/SchedulingSnippets.java[tag=snippet_6, indent=0]
----

== Reference

* https://github.com/jmrozanec/cron-utils[Cron-utils GitHub page]
* link:{scheduling-javadoc-base-url}/io/helidon/microprofile/scheduling/package-summary.html[Helidon Scheduling JavaDoc]