Change Tracking Plugin for SAP Cloud Application Programming Model (CAP)

a CDS plugin for automatic capturing, storing, and viewing of the change records of modeled entities

[!IMPORTANT] This release establishes compatibility with CDS 8.

Since the prior release was using APIs deprecated in CDS8, the code was modified significantly to enable compatibility. While we tested extensively, there may still be glitches or unexpected situations which we did not cover. So please test this release extensively before applying it to productive scenarios. Please also report any bugs or glitches, ideally by contributing a test-case for us to incorporate.

See the changelog for a full list of changes

Table of Contents

• Try it Locally
• Detailed Explanation
  • Human-readable Types and Fields
  • Human-readable IDs
  • Human-readable Values
• Advanced Options
  • Altered Table View
  • Disable Lazy Loading
  • Disable UI Facet generation
    • Disable Association to Changes Generation
• Examples
  • Specify Object ID
  • Tracing Changes
  • Don'ts
• Contributing
• Code of Conduct
• Licensing

Try it Locally

In this guide, we use the Incidents Management reference sample app as the base to add change tracking to.

1. Prerequisites
2. Setup
3. Annotations
4. Testing

1. Prerequisites

Clone the repository and apply the step-by-step instructions:

git clone https://github.com/cap-js/incidents-app
cd incidents-app
npm i

Alternatively, you can clone the incidents app including the prepared enhancements for change-tracking:

git clone https://github.com/cap-js/calesi --recursive
cd calesi
npm i

cds w samples/change-tracking

2. Setup

To enable change tracking, simply add this self-configuring plugin package to your project:

npm add @cap-js/change-tracking

3. Annotations

[!WARNING] Please be aware that sensitive or personal data (annotated with @PersonalData) is not change tracked, since viewing the log allows users to circumvent audit-logging.

All we need to do is to identify what should be change-tracked by annotating respective entities and elements in our model with the @changelog annotation. Following the best practice of separation of concerns, we do so in a separate file srv/change-tracking.cds:

using { ProcessorService } from './processor-service';

annotate ProcessorService.Incidents {
  customer @changelog: [customer.name];
  title    @changelog;
  status   @changelog;
}

annotate ProcessorService.Conversations with @changelog: [author, timestamp] {
  message  @changelog @Common.Label: 'Message';
}

The minimal annotation we require for change tracking is @changelog on elements, as for the elements title and status in the sample snippet above.

Additional identifiers or labels can be added to obtain more human-readable change records as described below.

4. Testing

With the steps above, we have successfully set up change tracking for our reference application. Let's see that in action.

1. Start the server:

cds watch

2. Make a change on your change-tracked elements. This change will automatically be persisted in the database table (sap.changelog.ChangeLog) and made available in a pre-defined view, namely the Change History view for your convenience.

Change History View

[!IMPORTANT] To ensure proper lazy loading of the Change History table, please use SAPUI5 version 1.120.0 or higher.<br> If you wish to disable this feature, please see the customization section on how to disable lazy loading.

If you have a Fiori Element application, the CDS plugin automatically provides and generates a view sap.changelog.ChangeView, the facet of which is automatically added to the Fiori Object Page of your change-tracked entities/elements. In the UI, this corresponds to the Change History table which serves to help you to view and search the stored change records of your modeled entities.

Detailed Explanation

Human-readable Types and Fields

By default the implementation looks up Object Type names or Field names from respective @title or @Common.Label annotations, and applies i18n lookups. If no such annotations are given, the technical names of the respective CDS definitions are displayed.

For example, without the @title annotation, changes to conversation entries would show up with the technical entity name:

With an annotation, and possible i18n translations like so:

annotate Conversations with @title: 'Conversations';

We get a human-readable display for Object Type:

Human-readable IDs

The changelog annotations for Object ID are defined at entity level.

These are already human-readable by default, unless the @changelog definition cannot be uniquely mapped such as types enum or Association.

For example, having a @changelog annotation without any additional identifiers, changes to conversation entries would show up as simple entity IDs:

However, this is not advisable as we cannot easily distinguish between changes. It is more appropriate to annotate as follows:

annotate ProcessorService.Conversations with @changelog: [author, timestamp] {

Expanding the changelog annotation by additional identifiers [author, timestamp], we can now better identify the message change events by their respective author and timestamp.

Human-readable Values

The changelog annotations for New Value and Old Value are defined at element level.

They are already human-readable by default, unless the @changelog definition cannot be uniquely mapped such as types enum or Association.

For example, having a @changelog annotation without any additional identifiers, changes to incident customer would show up as UUIDs:

customer @changelog;

Hence, here it is essential to add a unique identifier to obtain human-readable value columns:

customer @changelog: [customer.name];

Advanced Options

Altered table view

The Change History view can be easily adapted and configured to your own needs by simply changing or extending it. For example, let's assume we only want to show the first 5 columns in equal spacing, we would extend srv/change-tracking.cds as follows:

using from '@cap-js/change-tracking';

annotate sap.changelog.ChangeView with @(
  UI.LineItem : [
    { Value: modification, @HTML5.CssDefaults: { width:'20%' }},
    { Value: createdAt,    @HTML5.CssDefaults: { width:'20%' }},
    { Value: createdBy,    @HTML5.CssDefaults: { width:'20%' }},
    { Value: entity,       @HTML5.CssDefaults: { width:'20%' }},
    { Value: objectID,     @HTML5.CssDefaults: { width:'20%' }}
  ]
);

In the UI, the Change History table now contains 5 equally-spaced columns with the desired properties:

For more information and examples on adding Fiori Annotations, see Adding SAP Fiori Annotations.

Disable lazy loading

To disable the lazy loading feature of the Change History table, you can add the following annotation to your srv/change-tracking.cds:

using from '@cap-js/change-tracking';

annotate sap.changelog.aspect @(UI.Facets: [{
  $Type : 'UI.ReferenceFacet',
  ID    : 'ChangeHistoryFacet',
  Label : '{i18n>ChangeHistory}',
  Target: 'changes/@UI.PresentationVariant',
  ![@UI.PartOfPreview]
}]);

The system now uses the SAPUI5 default setting ![@UI.PartOfPreview]: true, such that the table will always shown when navigating to that respective Object page.

Disable UI Facet generation

If you do not want the UI facet added to a specific UI, you can annotate the service entity with @changelog.disable_facet. This will disable the automatic addition of the UI faced to this specific entity, but also all views or further projections up the chain.

Disable Association to Changes Generation

For some scenarios, e.g. when doing UNION and the @changelog annotion is still propageted, the automatic addition of the association to changes does not make sense. You can use @changelog.disable_assocfor this to be disabled on entity level.

[!IMPORTANT] This will also supress the addition of the UI facet, since the change-view is not available as target entity anymore.

Preserve change logs of deleted data

By default, deleting a record will also automatically delete all associated change logs. This helps reduce the impact on the size of the database. You can turn this behavior off globally by adding the following switch to the package.json of your project

...
"cds": {
  "requires": {
    ...
    "change-tracking": {
      "preserveDeletes": true
    }
   ...
  }
}
...

[!IMPORTANT] Preserving the change logs of deleted data can have a significant impact on the size of the change logging table, since now such data also survives automated data retention runs. You must implement an own data retention strategy for the change logging table in order to manage the size and performance of your database.

Examples

This section describes modelling cases for further reference, from simple to complex, including the following:

• Specify Object ID
  • Use Case 1: Annotate single field/multiple fields of associated table(s) as the Object ID
  • Use Case 2: Annotate single field/multiple fields of project customized types as the Object ID
  • Use Case 3: Annotate chained associated entities from the current entity as the Object ID
• Tracing Changes
  • Use Case 1: Trace the changes of child nodes from the current entity and display the meaningful data from child nodes (composition relation)
  • Use Case 2: Trace the changes of associated entities from the current entity and display the meaningful data from associated entities (association relation)
  • Use Case 3: Trace the changes of fields defined by project customized types and display the meaningful data
  • Use Case 4: Trace the changes of chained associated entities from the current entity and display the meaningful data from associated entities (association relation)
  • Use Case 5: Trace the changes of union entity and display the meaningful data
• Don'ts
  • Use Case 1: Don't trace changes for field(s) with Association to many
  • Use Case 2: Don't trace changes for field(s) with Unmanaged Association
  • Use Case 3: Don't trace changes for CUD on DB entity

Specify Object ID

Use cases for Object ID annotation

Use Case 1: Annotate single field/multiple fields of associated table(s) as the Object ID

Modelling in db/schema.cds

entity Incidents : cuid, managed {
  ...
  customer       : Association to Customers;
  title          : String @title: 'Title';
  urgency        : Association to Urgency default 'M';
  status         : Association to Status default 'N';
  ...
}

Add the following @changelog annotations in srv/change-tracking.cds

annotate ProcessorService.Incidents with @changelog: [customer.name, urgency.code, status.criticality] {
  title    @changelog;
}

Use Case 2: Annotate single field/multiple fields of project customized types as the Object ID

Modelling in db/schema.cds

entity Incidents : cuid, managed {
  ...
  customer       : Association to Customers;
  title          : String @title: 'Title';
  ...
}

entity Customers : cuid, managed {
  ...
  email          : EMailAddress;  // customized type
  phone          : PhoneNumber;   // customized type
  ...
}

Add the following @changelog annotations in srv/change-tracking.cds

annotate ProcessorService.Incidents with @changelog: [customer.email, customer.phone] {
  title    @changelog;
}

Use Case 3: Annotate chained associated entities from the current entity as the Object ID

Modelling in db/schema.cds

entity Incidents : cuid, managed {
  ...
  customer       : Association to Customers;
  ...
}

entity Customers : cuid, managed {
  ...
  addresses : Association to Addresses;
  ...
}

Add the following @changelog annotations in srv/change-tracking.cds

annotate ProcessorService.Incidents with @changelog: [customer.addresses.city, customer.addresses.postCode] {
  title    @changelog;
}

Change-tracking supports annotating chained associated entities from the current entity as object ID of current entity in case the entity in consumer applications is a pure relation table. However, the usage of chained associated entities is not recommended due to performance cost.

Tracing Changes

Use cases for tracing changes

Use Case 1: Trace the changes of child nodes from the current entity and display the meaningful data from child nodes (composition relation)

Modelling in db/schema.cds

entity Incidents : managed, cuid {
  ...
  title          : String @title: 'Title';
  conversation   : Composition of many Conversation;
  ...
}

aspect Conversation: managed, cuid {
    ...
    message   : String;
}

Add the following @changelog annotations in srv/change-tracking.cds

annotate ProcessorService.Incidents with @changelog: [title] {
  conversation @changelog: [conversation.message];
}

Use Case 2: Trace the changes of associated entities from the current entity and display the meaningful data from associated entities (association relation)

Modelling in db/schema.cds

entity Incidents : cuid, managed {
  ...
  customer       : Association to Customers;
  title          : String @title: 'Title';
  ...
}

entity Customers : cuid, managed {
  ...
  email          : EMailAddress;
  ...
}

Add the following @changelog annotations in srv/change-tracking.cds

annotate ProcessorService.Incidents with @changelog: [title] {
  customer @changelog: [customer.email];
}

Use Case 3: Trace the changes of fields defined by project customized types and display the meaningful data

Modelling in db/schema.cds

type StatusType : Association to Status;

entity Incidents : cuid, managed {
  ...
  title          : String @title: 'Title';
  status         : StatusType default 'N';
  ...
}

Add the following @changelog annotations in srv/change-tracking.cds

annotate ProcessorService.Incidents with @changelog: [title] {
  status   @changelog: [status.code];
}

Use Case 4: Trace the changes of chained associated entities from the current entity and display the meaningful data from associated entities (association relation)

Modelling in db/schema.cds

entity Incidents : cuid, managed {
  ...
  title          : String @title: 'Title';
  customer       : Association to Customers;
  ...
}

entity Customers : cuid, managed {
  ...
  addresses : Association to Addresses;
  ...
}

Add the following @changelog annotations in srv/change-tracking.cds

annotate ProcessorService.Incidents with @changelog: [title] {
  customer @changelog: [customer.addresses.city, customer.addresses.streetAddress];
}

Change-tracking supports analyzing chained associated entities from the current entity in case the entity in consumer applications is a pure relation table. However, the usage of chained associated entities is not recommended due to performance cost.

Use Case 5: Trace the changes of union entity and display the meaningful data

Payable.cds:

entity Payables : cuid {
    displayId    : String;
    @changelog
    name         : String;
    cryptoAmount : Decimal;
    fiatAmount   : Decimal;
};

Payment.cds:

entity Payments : cuid {
    displayId : String; //readable ID
    @changelog
    name      : String;
};

Union entity in BusinessTransaction.cds:

entity BusinessTransactions          as(
    select from payments.Payments{
        key ID,
            displayId,
            name,
            changes  : Association to many ChangeView
                on changes.objectID = ID AND changes.entity = 'payments.Payments'
    }
)
union all
(
    select from payables.Payables {
        key ID,
            displayId,
            name,
            changes  : Association to many ChangeView
               on changes.objectID = ID AND changes.entity = 'payables.Payables'
    }
);

Don'ts

Don'ts

Use Case 1: Don't trace changes for field(s) with Association to many

entity Customers : cuid, managed {
  ...
  incidents : Association to many Incidents on incidents.customer = $self;
}

The reason is that: the relationship: Association to many is only for modelling purpose and there is no concrete field in database table. In the above sample, there is no column for incidents in the table Customers, but there is a navigation property of incidents in Customers OData entity metadata.

Use Case 2: Don't trace changes for field(s) with Unmanaged Association

entity AggregatedBusinessTransactionData @(cds.autoexpose) : cuid {
    FootprintInventory: Association to one FootprintInventories
                        on  FootprintInventory.month                      = month
                        and FootprintInventory.year                       = year
                        and FootprintInventory.FootprintInventoryScope.ID = FootprintInventoryScope.ID;
    ...
}

The reason is that: When deploying to relational databases, Associations are mapped to foreign keys. Yet, when mapped to non-relational databases they're just references. More details could be found in Prefer Managed Associations. In the above sample, there is no column for FootprintInventory in the table AggregatedBusinessTransactionData, but there is a navigation property FootprintInventoryof in OData entity metadata.

Use Case 3: Don't trace changes for CUD on DB entity

this.on("UpdateActivationStatus", async (req) =>
    // PaymentAgreementsOutgoingDb is the DB entity
    await UPDATE.entity(PaymentAgreementsOutgoingDb)
        .where({ ID: paymentAgreement.ID })
        .set({ ActivationStatus_code: ActivationCodes.ACTIVE });
);

The reason is that: Application level services are by design the only place where business logic is enforced. This by extension means, that it also is the only point where e.g. change-tracking would be enabled. The underlying method used to do change tracking is req.diff which is responsible to read the necessary before-image from the database, and this method is not available on DB level.

Contributing

This project is open to feature requests/suggestions, bug reports etc. via GitHub issues. Contribution and feedback are encouraged and always welcome. For more information about how to contribute, the project structure, as well as additional contribution information, see our Contribution Guidelines.

Code of Conduct

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Licensing

Copyright 2023 SAP SE or an SAP affiliate company and contributors. Please see our LICENSE for copyright and license information. Detailed information including third-party components and their licensing/copyright information is available via the REUSE tool.