Ressources

partly described in Tutorial System Hooks

Introduction

Main part(s)

This tutorial shows how to set up an AMQP system hook to generate a message when importing a document. We’ll go through an example in which we’ll configure a system hook that sends messages to a messaging system to perform an asynchronous full-text indexing (more about asynchronous full-text indexing can be found here).

Requirements

This tutorial requires:

• Basic knowledge of importing documents
• A messaging system supporting AMQP 1.0

Table of Contents

• Requirements
• Introduction
• Configuring the AMQP System Hook
• Activating the AMQP System Hook
• Conclusion

Introduction

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With an AMQP Hook, messages are sent to a configured messaging system

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using Advanced Message Queuing Protocol 1.0 (AMPQ). Where and when these messages are sent is defined in the

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System Hook configuration.

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System hooks are configured in the file \service-manager\config\system\systemHookConfiguration.json in json format. 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

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Type

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Description

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enable

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predicate

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Condition that specifies when the system hook is used. Supported scripting languages: Spring Expression Language (SpEL) und Javascript.

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type

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url

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user

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password

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queue

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bulkSize

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Configuring the AMQP System Hook

We configure an AMQP system hook to send messages to a messaging system when importing compound documents. For this we use the following configuration:
systemHookConfiguration.json

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{
    "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
            }
        ]
    }
}

For AMQP, this configuration has exactly one system hook of type object.insert.document relevant to the API-Gateway. If the evaluation of the predicate for a document on import results in true (in our example only for compound documents), the API-Gateway 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.

Activating the AMQP System Hook

In our example of asynchronous full-text indexing, the API-Gateway is responsible for evaluating the system hook. To apply the configuration, the API-Gateway must be restarted after saving the configuration file. Messages will then be send to the messaging system for the import of compound documents.

Conclusion

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 Any changes to the System Hook configuration will not apply until the affected services have been restarted.

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.

Types of AMQP Hooks

Configuring AMQP Hooks

As a type of system hooks, AMQP Hooks 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

Summary

In this article, we gave an introduction to AMQP Hooks, covered the configuration using the example of asynchronous full text indexing

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Subsection(s)

for (int i = 0; i < 10; i++)
{
	System.out.println("Hello World " + i);
}

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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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Another Tutorial

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Another interesting Tutorial

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Another Concept Article

Brief summary of the article linked.