A system hook that extends a function call by an HTTP call under defined conditions.

Introduction

In order to insert an additional action into the process flow of a functional sequence, the ability for reacting to a function call is required. In yuuvis® Momentum, webhooks are a suitable option for this purpose. They belong to the system hooks and thus are triggered by function calls under specified conditions defined on their predicate attribute.

A webhook extends the function by an HTTP call. Whenever the predicate of a webhook delivers a true result, an optional HTTP call to a web URL defined in the webhook configuration is performed. The process flow is interrupted until the webhook activity is finished. Thus, the webhook can perform additional processing steps before passing the data back to resume the interrupted main process. If the predicate of a webhook delivers a false result, the HTTP call is skipped.

For the additional processing, a custom service has to be implemented. This service must be able to handle the request body and the assigned headers. Please note the maximum header size that should be supported by your custom service.

Import and content update webhooks are called in the Repository service, all others in the API-gateway service.

Any changes to the webhook configuration require a restart of the services that are responsible for the call of the affected functions.

Webhook Types

Depending on their type, webhooks are triggered in different situations within the data processing chain.

The webhook type dms.response.objects can be triggered in various situations. For some of them there are special webhook types (dms.response.objects.insert, dms.response.objects.update, dms.response.objects.search, dms.response.objects.delete). These sub-webhooks are triggered directly after dms.response.objects.

HTTP Method	Webhook Type	Evaluation Target of the Predicate	Description	Affected Requests
GET	user.info	The tenant name of the user who sent the request.	Retrieves roles and any additional available information about the current user logging in to the authentication system from the URL.	Authentication process
POST	dms.request.objects.upsert.storage-before	Objects provided by an import request body	This webhook can be triggered by an object import, an update of the content, an update or the metadata, or a tag update.	POST /api/dms/objects POST /api/dms/objects/{objectId} PATCH /api/dms/objects/{objectId} POST /api/dms/objects/{objectId}/contents/file POST /api/dms/objects/{objectId}/versions/{versionNr}/actions/restore (as of 2022 Spring) POST /api/dms/objects/tags/{name}/state/{state}?query=<SQL> DELETE /api/dms/objects/{objectId}/tags/{name} POST /api/dms/objects/{objectId}/tags/{name}/state/{state} POST /api/dms/objects/{objectId}/tags/{name}/state/{state}?overwrite=true
POST as of 2021 Autumn	dms.request.objects.upsert.database-before	Enriched objects just before they are indexed	This webhook can be triggered by an object import, an update of the content, an update or the metadata, or a tag update.	POST /api/dms/objects POST /api/dms/objects/{objectId} PATCH /api/dms/objects/{objectId} POST /api/dms/objects/{objectId}/contents/file POST /api/dms/objects/{objectId}/versions/{versionNr}/actions/restore (as of 2022 Spring) POST /api/dms/objects/tags/{name}/state/{state}?query=<SQL> DELETE /api/dms/objects/{objectId}/tags/{name} POST /api/dms/objects/{objectId}/tags/{name}/state/{state} POST /api/dms/objects/{objectId}/tags/{name}/state/{state}?overwrite=true
POST	dms.request.update.metadata (deprecated)	Single object in the request body JSON list	Triggers upon metadata updates, before the JSON request body is evaluated and used to update the object. Can be used to modify or validate the metadata, i.e., to facilitate role-based user authorization.	POST /api/dms/objects/{objectId} PATCH /api/dms/objects/{objectId}
POST	dms.request.search	Incoming search queries	The search endpoint and any endpoint containing a search request can trigger this webhook. Check the value of the incoming search query parameter.	POST /api/dms/objects/search POST /api/dms/objects/tags/{name}/state/{state}?query=<SQL>
POST (as of 2022 Winter)	dms.request.objects.contents	DMS object as stored in the system including metadata properties, content stream properties and options sections.	A webhook of this type can be triggered by a request for retrieval of a binary content file or a rendition. Errors with a properly formatted body get the HTTP status code 404.	GET /api/dms/objects/{objectId}/contents/file GET /api/dms/objects/{objectId}/versions/{versionNr}/contents/file GET /api/dms/objects/{objectId}/contents/renditions/text GET /api/dms/objects/{objectId}/contents/renditions/pdf GET /api/dms/objects/{objectId}/versions/{versionNr}/contents/renditions/pdf
POST	dms.request.objects.delete	The active version of the object or the specific version that is to be deleted	The webhook is triggered if the object or version to delete exists and is deletable, i.e., if the user has sufficient permissions and if the object is not a non-empty folder.	DELETE /api/dms/objects/{objectId} DELETE /api/dms/objects DELETE /api/dms/objects/{objectId}/versions/{versionNr}
POST	dms.response.objects	Objects within a list of objects that is to be returned to the user, i.e., in search queries	Delivers a list of predicate-matching objects to a secondary recipient. Any request returning an object list triggers this webhook directly before the return. Applies whenever object lists are part of the HTTP response: Search queries Object Iiports Object GETs Object metadata updates Moving content	POST /api/dms/objects POST /api/dms/objects/{objectId} PATCH /api/dms/objects/{objectId} POST /api/dms/objects/{objectId}/contents/file DELETE /api/dms/objects/{objectId} DELETE /api/dms/objects DELETE /api/dms/objects/{objectId}/tags/{name} POST /api/dms/objects/{objectId}/tags/{name}/state/{state} POST /api/dms/objects/tags/{name}/state/{state}?query=<SQL> POST /api/dms/objects/{objectId}/tags/{name}/state/{state}?overwrite=true POST /api/dms/objects/search POST /api/dms/objects/{objectId}/actions/move/contents/repositories/{repositoryId} POST /api/dms/objects/{objectId}/versions/{versionNr}/actions/move/contents/repositories/{repositoryId} GET /api/dms/objects/{objectId} GET /api/dms/objects/{objectId}/versions GET /api/dms/objects/{objectId}/versions/{versionNr} POST /api/dms/objects/{objectId}/versions/{versionNr}/actions/restore (as of 2022 Spring) DELETE /api/dms/objects/{objectId}/versions/{versionNr}
POST	dms.response.objects.insert	The final object after import	Import requests trigger this webhook after successful import directly before the return.	POST /api/dms/objects
POST	dms.response.objects.update	The object after the update	Update requests trigger this webhook after successful update directly before the return. This concerns content updates, metadata updates and tag updates.	POST /api/dms/objects/{objectId} PATCH /api/dms/objects/{objectId} POST /api/dms/objects/{objectId}/contents/file POST /api/dms/objects/{objectId}/versions/{versionNr}/actions/restore (as of 2022 Spring) POST /api/dms/objects/tags/{name}/state/{state}?query=<SQL> DELETE /api/dms/objects/{objectId}/tags/{name} POST /api/dms/objects/{objectId}/tags/{name}/state/{state} POST /api/dms/objects/{objectId}/tags/{name}/state/{state}?overwrite=true
POST	dms.response.objects.delete	The active version of the object or the specific version that is deleted	This webhook is triggered directly after the successful deletion of a document and after the equivalent AMQP hook, and can for instance inform other systems.	DELETE /api/dms/objects/{objectId} DELETE /api/dms/objects DELETE /api/dms/objects/{objectId}/versions/{versionNr}
POST	dms.response.objects.search	Search result entry	Search requests trigger this webhook if they were successful directly before the return.	POST /api/dms/objects/search

Predicate

The predicate specifies the condition for the call of individual webhooks. It is declared in the webhook configuration.

If multiple webhooks are registered for the same webhook type, the predicate is applied to the original predicate target for each of them and in the order of definition. Imagine an example scenario with two registered webhooks of the type dms.response.objects.search:

{
    "enable": true,
    "predicate": "spel:true",
    "type": "dms.response.objects.search",
    "url": <suitable endpoint removing the property 'appEmail:bcc'>,
    "useDiscovery": true
},
{
    "enable": true,
    "predicate": "spel:properties['appEmail:bcc']!=null",
    "type": "dms.response.objects.search",
    "url": <any suitable endpoint>,
    "useDiscovery": true
}

If objects in a search result have the appEmail:bcc property and the first webhook removes this property from the objects, the predicate of the second webhook still matches.

The same behavior holds for the webhook type dms.response.objects and one of its sub-webhook types dms.response.objects.*:

{
    "enable": true,
    "predicate": "spel:true",
    "type": "dms.response.objects",
    "url": <suitable endpoint removing the property 'appEmail:bcc'>,
    "useDiscovery": true
},
{
    "enable": true,
    "predicate": "spel:properties['appEmail:bcc']!=null",
    "type": "dms.response.objects.search",
    "url": <any suitable endpoint>,
    "useDiscovery": true
}

Configuring Webhooks

As a type of system hooks, webhooks are configured in the \service-manager\config\system\systemHookConfiguration.json configuration file within the service manager in JSON format. Any changes to the system hook configuration will not apply until the affected services have been restarted.

>> systemHookConfiguration.json

The timeouts that limit the process time of webhooks in order to avoid system bottlenecks are configured in the application-prod.yml configuration file as shown in the following example:

service:
  connection-timeout-ms: 3000
  socket-timeout-ms: 10000

Loggers for Webhooks

As of version 2022 Spring, the input and output data for each webhook can be monitored via loggers.
>> Logging Configuration

The logging level can be specified

for all webhooks, e.g., os.dev.webhooks=DEBUG, or
for individual webhook types, e.g., os.dev.webhooks.dms.request.search=DEBUG.

The logging configuration for each webhook has to be read by the service that calls the webhook. For the individual webhook types, different services are responsible. Thus, please ensure that your webhook logging configuration is defined in a configuration file that is read by its calling service. In order to apply the configuration changes, each calling service has to be refreshed or restarted.

Depending on the logging level, the following details are logged:

Logging Level Logged Information

Logging Level	Logged Information
`DEBUG`	Only enabled webhooks are considered. The following data are logged: boolean result of the predicate evaluation predicate evaluation target if the predicate is true: input and output data of the webhook including the headers
`TRACE`	For enabled webhooks, the same information is logged as is the case for the DEBUG logging level. Disabled webhooks are listed together with the information: `Webhook` `not` `enabled`.

DEBUG

Only enabled webhooks are considered. The following data are logged:

boolean result of the predicate evaluation
predicate evaluation target
if the predicate is true: input and output data of the webhook including the headers

TRACE

For enabled webhooks, the same information is logged as is the case for the DEBUG logging level.

Disabled webhooks are listed together with the information: Webhook not enabled.

Summary

This article gave an overview of the webhook types that are available in yuuvis® Momentum. Check out the "Preprocessing Metadata using Webhooks" tutorial for an example application which shows different webhook types.

Table of Contents

Introduction

Webhook Types

Predicate

Configuring Webhooks

Loggers for Webhooks

Summary

Read on

Preprocessing Metadata using Webhooks

System Hooks

Basic Use Case Flows

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