[[commandlog]]
= Command Log

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The _Command Log_ module provides an implementation of xref:refguide:applib:index/services/publishing/spi/CommandSubscriber.adoc[] SPI that persists xref:refguide:applib:index/services/command/Command.adoc[Command]s using either the xref:pjpa:ROOT:about.adoc[JPA/EclipseLink] or xref:pjdo:ROOT:about.adoc[JDO/DataNucleus] object store.

One use case is to combine with the xref:security:audittrail:about.adoc[] extension.
The _Command Log_ module logs the action invocations or property edits that the end-user makes, while the _audit trail_ logs the resultant changes in state to domain objects.
The two logs are correlated using the xref:refguide:applib:index/services/iactn/Interaction.adoc#getInteractionId_[interactionId] of the owning xref:refguide:applib:index/services/iactn/Interaction.adoc[interaction].

Another use case is to support (persisted) background commands, whereby actions are not invoked immediately but instead persisted and invoked by a background thread; this is described in the xref:#background-commands[background commands] section below.

Sometimes the xref:executionlog:about.adoc[] extension is also configured with or instead of this extension; see the xref:#notes[notes] below to compare and contrast.



== Setup

=== Dependency Management

Add an entry for the _Command Log_ module's own BOM:

[source,xml,subs="attributes+"]
.pom.xml
----
<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.apache.causeway.extensions</groupId>
            <artifactId>causeway-extensions-commandlog</artifactId>
            <scope>import</scope>
            <type>pom</type>
            <version>{page-causewayprev}</version>
        </dependency>
    </dependencies>
</dependencyManagement>
----

[#dependencies]
=== Dependencies / Imports

In the webapp module of your application, add the following dependency:

[source,xml]
.pom.xml
----
<dependencies>
    <dependency>
        <groupId>org.apache.causeway.extensions</groupId>
        <artifactId>causeway-extensions-commandlog-persistence-XXX</artifactId>    <!--.-->
    </dependency>
</dependencies>
----
<.> either:
** `causeway-extensions-commandlog-persistence-jpa` (xref:pjpa::about.adoc[]), or
** `causeway-extensions-commandlog-persistence-jdo` (xref:pjdo::about.adoc[]).


In your application's xref:userguide::modules.adoc#appmanifest[App Manifest], import the CommandLog modules.
The exact modules to use will depend upon the persistence mechanism in use:

[source,java]
.AppManifest.java
----
@Configuration
@Import({
        ...
        CausewayModuleExtCommandLogPersistenceXxx.class,        // <.>
        ...
})
public class AppManifest {
}
----
<.> either
** `CausewayModuleExtCommandLogPersistenceJpa` (xref:pjpa::about.adoc[]),or
** `CausewayModuleExtCommandLogPersistenceJdo`, (xref:pjdo::about.adoc[])

If using xref:security:secman:about.adoc[], you will also need to import the xref:testing:fixtures:about.adoc[Fixture] module; SecMan uses fixture scripts to seed its entities.


[#configure-properties]
=== Configuration Properties

Add the database schema used by the _Command Log_ entities to the configuration file:

[source,yaml]
.application.yml
----
causeway:
  persistence:
    schema:
      auto-create-schemas: causewayExtCommandLog
----

Optionally, modify the configuration properties for the _Command Log_ module itself:

[source,yaml]
.application.yml
----
causeway:
  extensions:
    command-log:
      publish-policy: "always"    # <.>
----


<.> the alternative is `"only-if-system-changed"`, which suppresses the persisting of `CommandLogEntry`s for commands where no other system state was changed (for example a finder action with safe semantics).
+
See xref:refguide:config:sections/causeway.extensions.adoc#causeway.extensions.command-log.publish-policy[causeway.extensions.command-log.publish-policy] configuration property for more details.


[#menubar-layout-xml]
=== menubar.layout.xml

Once configured, the extension provides a number of menu actions.
You can use `menubars.layout.xml` to arrange these as you see fit.
To get you started, the following fragment adds all of the actions to an "Activity" secondary menu:

[source,xml]
.menubars.layout.xml
----
<mb:secondary>
    ...
    <mb:menu>
        <mb:named>Activity</mb:named>
        ...
        <mb:section>
            <mb:named>Commands</mb:named>
            <mb:serviceAction id="activeCommands" objectType="causeway.ext.commandLog.CommandLogMenu"/>
            <mb:serviceAction id="findMostRecent" objectType="causeway.ext.commandLog.CommandLogMenu"/>
            <mb:serviceAction id="findCommands" objectType="causeway.ext.commandLog.CommandLogMenu"/>
            <mb:serviceAction id="findAll" objectType="causeway.ext.commandLog.CommandLogMenu"/>
        </mb:section>
        ...
    </mb:menu>
</mb:secondary>
----

[#secman-security-roles]
=== SecMan Security Roles

If xref:security:secman:about.adoc[] extension is configured, then permissions must be granted to access the menu actions.

This can be done by granting the role set up by the xref:refguide:extensions:index/secman/applib/role/seed/CausewayExtCommandLogRoleAndPermissions.adoc[] seed fixture script (see its `ROLE_NAME` constant).


== User Interface

The extension provides a number of menu actions and contributions.

The menu actions are as listed in xref:menubar-layout-xml[], above.
They allow the administrator to query the persisted commands.
Typically access to these actions would be restricted, see xref:secman-security-roles[security roles] above.

The extension also provides these mixins:

* xref:refguide:extensions:index/commandlog/applib/contributions/Object_recentCommands.adoc[]
+
This contributes a `recentCommands` collection to each and every domain object.
+
This can be explicit positioned through the domain class' own xref:userguide:ROOT:ui-layout-and-hints.adoc#object-layout[layout file], but this is generally not necessary: it will slot into the tab group in the layout file indicated for unreferenced collections using `<tabGroup unreferencedCollections="true">`.

* xref:refguide:extensions:index/commandlog/applib/contributions/HasUsername_recentCommandsByUser.adoc[]
+
This contributes the `recentCommandsByUser` collection to any domain object that implements the xref:refguide:applib:index/mixins/security/HasUsername.adoc[] interface.
+
Most notably, this is xref:security:secman:about.adoc[] extension's xref:refguide:extensions:index/secman/applib/user/dom/ApplicationUser.adoc[] entity that represents a logged-on user.
It is also supported by xref:security:sessionlog:about.adoc

* xref:refguide:extensions:index/commandlog/applib/contributions/HasInteractionId_commandLogEntry.adoc[]
+
This contributes the `commandLogEntry` property to any object implementing xref:refguide:applib:index/mixins/system/HasInteractionId.adoc[] interface.
Typically these are the entities persisted by the xref:executionlog:about.adoc[] or xref:security:audittrail:about.adoc[] extensions, making it easy to traverse between these logs.


[#background-commands]
== Background Commands

Sometimes we might want to execute an action not immediately in the current users's thread of control, but instead to perform it in the background; for example any long-running process.

One way to accomplish this is to use xref:refguide:applib:index/services/wrapper/WrapperFactory.adoc#asyncWrap_T_AsyncControl[WrapperFactory#asyncWrap(...)], where the command is executed by another thread obtained from a thread pool (`ForkJoinPool.commonPool()`).
This works well, but has the slight risk that it is not transactionally safe - the async thread executes in its own interaction/transaction, and so might fail even though the initiating command succeeds; or vice versa.

An alternative approach is to use the xref:refguide:extensions:index/commandlog/applib/dom/BackgroundService.adoc[BackgroundService].
This persists the command as an `CommandLogEntry` instance, indicating that it is to be executed in the background.
Then, a separate thread - eg scheduling using Quartz - can pick up the queued `CommandLogEntry` and execute it.

=== Submitting Actions

For example, suppose we have a long-running action to export all the invoices we have received from a supplier, perhaps to be sent to some other system.
Assuming that the `exportInvoices()` action is a regular action on the `Supplier` domain class, we would use:

[source,java]
.example usage of `BackgroundService` to invoke a regular action
----
@Action
public void exportInvoices(Supplier supplier) {
    backgroundService.execute(supplier).exportInvoices();
}
----

If instead this functionality is implemented as a mixin, we would use something like:

[source,java]
.example usage of `BackgroundService` to invoke a mixin action:
----
@Action
public void exportInvoices(Supplier supplier) {
    backgroundService.executeMixin(Supplier_exportInvoices.class, supplier).act();
}
----

The action being invoked must be part of the Causeway metamodel, in other words it cannot be marked uses
xref:refguide:applib:index/annotation/Programmatic.adoc[] or xref:refguide:applib:index/annotation/Domain_Exclude.adoc[].

By default all the usual hide/disable/validate rules will be checked, but there are also methods to allow these rules to be skipped.

Behind the scenes this service uses xref:refguide:applib:index/services/wrapper/WrapperFactory.adoc#asyncWrap_T_AsyncControl[WrapperFactory#asyncWrap(...)] using xref:refguide:applib:index/services/wrapper/control/AsyncControl.adoc#with_ExecutorService[AsyncControl#with(ExecutorService)] to pass an implementation of `ExecutorService` that persists the command as a `CommandLogEntry` instance.

If you require more fine-grained control, you can always just use the xref:refguide:applib:index/services/wrapper/WrapperFactory.adoc[WrapperFactory] async method yourself.
The `ExecutorService` to use is xref:refguide:extensions:index/commandlog/applib/dom/BackgroundService_PersistCommandExecutorService.adoc[BackgroundService.PersistCommandExecutorService].
This is a Spring `@Service` and so can be obtained through injection.

=== Executing Actions using the Quartz scheduler

Once a command has been persisted as a `CommandLogEntry`, we require some other process to actually execute the command.
The _Command Log_ module includes the `RunBackgroundCommandsJob`, a https://www.quartz-scheduler.org/[Quartz] job that does exactly this.
Each time it is called it will query for any background commands that have not been started, and will execute each (using the xref:refguide:applib:index/services/command/CommandExecutorService.adoc[CommandExecutorService]).

The job is marked as non re-entrant, so it doesn't matter how often it is called; we recommend a 10 second delay usually works fine.

To configure Quartz, add the following to your `AppManifest`:

[source,java]
.AppManifest.java
----
public class AppManifest {

    @Bean(name = "RunBackgroundCommandsJob")                                // <.>
    public JobDetailFactoryBean jobDetail() {
        val jobDetailFactory = new JobDetailFactoryBean();
        jobDetailFactory.setJobClass(RunBackgroundCommandsJob.class);
        jobDetailFactory.setDurability(true);
        return jobDetailFactory;
    }

    @Bean
    public SimpleTriggerFactoryBean trigger(
            final @Qualifier("RunBackgroundCommandsJob") JobDetail job) {   // <1>
        val trigger = new SimpleTriggerFactoryBean();
        trigger.setJobDetail(job);
        trigger.setStartDelay(60_000);                                      // <.>
        trigger.setRepeatInterval(10_000);                                  // <.>
        trigger.setRepeatCount(REPEAT_INDEFINITELY);
        return trigger;
    }

    // ...
}
----

<.> name and qualify the job (so will not interfere with any other Quartz jobs you may have defined)
<.> 60 secs to wait for the app to be ready
<.> check every 10 seconds



==== Disabling Quartz

The _Command Log_ module automatically references the https://www.quartz-scheduler.org/[Quartz] library.
If you don't want to use this functionality and want to exclude quartz, then add an explicit dependency on the _Command Log_ applib but exclude the quartz dependency within it:

[source,xml]
.pom.xml
----
<dependencies>
    <dependency>
        <groupId>org.apache.causeway.extensions</groupId>
        <artifactId>causeway-extensions-commandlog-applib</artifactId>
        <exclusions>
            <exclusion>
                <groupId>org.quartz-scheduler</groupId>                 <!--.-->
                <artifactId>quartz</artifactId>
            </exclusion>
        </exclusions>
    </dependency>
</dependencies>
----
<.> exclude reference to quartz



[#notes]
== Notes

include::partial$commandsubscriber-vs-executionsubscriber.adoc[]



== See also

* xref:refguide:applib:index/services/iactn/Interaction.adoc[interaction]
* xref:refguide:applib:index/services/iactnlayer/InteractionService.adoc[].
* xref:refguide:applib:index/services/wrapper/WrapperFactory.adoc[] service
* xref:refguide:extensions:index/commandlog/applib/dom/BackgroundService.adoc[BackgroundService] service
* xref:refguide:applib:index/services/publishing/spi/CommandSubscriber.adoc[] SPI
* xref:refguide:applib:index/services/publishing/spi/ExecutionSubscriber.adoc[] SPI
* xref:executionlog:about.adoc[] extension

