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The AMQP Hooks allow for asynchronous reactions to events like object creation, update or deletion. There are different types of AMQP Hooks available, each of them specialized for selected function calls. The messages contain the object metadata which is the target of the function call triggering the AMQP Hook. The action code is included in the message as well as the history code that is added to the audit trail. The AMQP Hook can be triggered by any endpoint that induced the characteristic history codes of the AMQP Hook.
AMQP Hook Configuration
Parameters
The AMQP configuration is located in the amqp key under the systemhooks top-level key. It is represented as a list of one or more System Hooks whose parameters are described in the table below:
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Parameter
Types of AMQP Hooks
AMQP Hook Type | Description |
|---|
enablebooleanpredicatestringcondition that specifies when the system hook is used
supported scripting languages: SpEL (Spring Expression Language) and Javascript.
typestringurlstring127.0.0.1:5672userstringpasswordstringqueuestringbulkSizeintegerExample Configuration
The parameters of the AMQP Hook are specified in JSON format. In the \service-manager\config\system\systemHookConfiguration.json configuration file, multiple AMQP Hooks can be defined in a list called amqp. It must however be observed that only one messaging queue can be used. The messaging queue specified for the first defined AMQP Hook will apply to all following AMQP Hook definitions as well. Of course, the messaging system needs to support AMQP 1.0. Any changes to the AMQP Hook configuration require a restart of the API-gateway service.
The example code below configures an AMQP Hook triggered by a document import. This configuration has exactly one System Hook, which is an AMQP Hook of the type object.insert.document. If the evaluation of the predicate for a document on import results is true (in our example only for compound documents), the API-gateway service sends a message with the metadata of the document to the defined messaging system. In addition, the configuration specifies a bulkSize of 10, i.e. for a batch import of 100 documents matching the predicate, 10 messages with 10 metadata entries per message are written to the queue named lc.textextraction.
| Code Block | ||||
|---|---|---|---|---|
| ||||
{
"systemhooks": {
"amqp": [
{
"enable": true,
"predicate": "spel:(contentStreams != null && contentStreams.size() > 0 && contentStreams[0]['range'] != null && contentStreams[0]['range'].length() > 0) ? true : false",
"type": "object.insert.document",
"url": "127.0.0.1:5672",
"user": "admin",
"password": "admin_pwd",
"queue": "lc.textextraction",
"bulkSize": 10
}
]
}
} |
Activating the AMQP Hook
In our example of asynchronous full-text indexing, the API-gateway service is responsible for evaluating the system hook. To apply the configuration, the API-gateway service must be restarted after saving the configuration file. Messages will then be send to the messaging system for the import of compound documents.
Types of AMQP Hooks
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| Action / History Codes | ||
|---|---|---|
| Object deletion events can trigger this AMQP Hook with the corresponding object properties in its body. | 200 - OBJECT_DELETED 202 - OBJECT_FLAGGED_FOR_DELETE | |
Object creation events can trigger this AMQP Hook with the corresponding object properties in its body. | 101 - OBJECT_CREATED_WITH_CONTENT | |
Object update events and tag operations can trigger this AMQP Hook with the corresponding object properties in its body. | 300 - OBJECT_METADATA_CHANGED |
Summary
In this article, we gave an introduction to AMQP Hooks, covered the configuration using the example of asynchronous full text indexing and provide a list of all AMQP Hooks available. Check out Webhooks which are the second type of System Hooks in yuuvis® Momentum.
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