4. Configuration

4.1. Configuring Web Integration Service

When you start Web Integration Service, you can specify a configuration file in XML format (it is not required). In that file, you can set properties that control the behavior of the service.

• Section 4.3 discusses how the file is loaded.

• Section 4.4 explains its syntax and validation.

• Section 4.5 describes how to write a configuration file.

• Section 4.6 explains how to configure the Authentication and Access Control mechanisms included with Web Integration Service.

4.2. Terms to Know

Before learning how to configure Web Integration Service, you should become familiar with a few key terms and concepts:

• A Web Integration Service configuration—represented by the <web_integration_service> XML tag—refers to an execution of Web Integration Service.

• An Application—represented by the <application> XML tag—defines a collection of DomainParticipants and their contained entities. Applications are instantiated in the context of a Web Integration Service configuration. That is, a Web Integration Service configuration contains a set of applications that contain entities that are accessible for clients of the service.

4.3. How to Load the XML Configuration

Web Integration Service loads its XML configuration from multiple locations. This section presents the various approaches, listed in load order.

The first three locations are inherited from Connext DDS (see the RTI Connext DDS Core Libraries User’s Manual).

• $NDDSHOME/resource/xml/NDDS_QOS_PROFILES.xml This file contains the Connext DDS default QoS values; it is loaded automatically if it exists. (First to be loaded.).

• File specified in the NDDS_QOS_PROFILES environment variable: The files (or XML strings) separated by semicolons referenced in this environment variable are loaded automatically.

• <working directory>/USER_QOS_PROFILES.xml This file is loaded automatically if it exists.

The next locations are specific to Web Integration Service.

• $NDDSHOME/resource/xml/RTI_WEB_INTEGRATION_SEVICE.xml This file contains the default Web Integration Service configuration; it is loaded if it exists. It defines an empty service that clients can add applications to, as well as an example “ShapesDemo” service.

• <working directory>/USER_WEB_INTEGRATION_SERVICE.xml This file is loaded automatically if it exists.

• File specified using the command-line parameter -cfgFile.

You may use a combination of the above approaches.

Here is an example configuration file. You will learn the meaning of each line as you read the rest of this section.

<?xml version="1.0" encoding="UTF-8"?>
<dds>
    <types>
        <struct name="MyType">
            <member name="name" key="true"
                    type="string" stringMaxLength="128"/>
            <member name="count" type="long" />
        </struct>
    </types>
    <web_integration_service name="ExampleService">
        <application name="MyApplication">
            <domain_participant name="MyParticipant" domain_id="32">
                <register_type name="MyShapeType" type_ref="ShapeType" />
                <topic name="Square" register_type_ref="MyShapeType" />
                <publisher name="MyPublisher">
                    <data_writer name="MySquareWriter" topic_ref="Square" />
                </publisher>
                <subscriber>
                    <data_reader name="MySquareReader" topic_ref="Square" />
                </subscriber>
            </domain_participant>
        </application>
    </web_integration_service>
</dds>

4.4. XML Syntax and Validation

Web Integration Service provides DTD and XSD files that describe the format of the XML content. We recommend including a reference to one of these documents in the XML file that contains the service’s configuration—this provides helpful features in code editors such as Visual Studio® and Eclipse®, including validation and autocompletion while you are editing the XML file.

The DTD and XSD definitions of the XML elements are in $NDDSHOME/resource/schema/rti_web_integration_service.dtd and $NDDSHOME/resource/schema/rti_web_integration_service.xsd, respectively.

To include a reference to the XSD document in your XML file, use the attribute xsi:noNamespaceSchemaLocation in the <dds> tag. For example:

<?xml version="1.0" encoding="UTF-8"?>
<dds xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:noNamespaceSchemaLocation="<NDDSHOME>/resource/schema/rti_web_integration_service.xsd">
  <!-- ... -->
</dds>

To include a reference to the DTD document in your XML file, use the <!DOCTYPE> tag. For example:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE dds SYSTEM
    "<NDDSHOME>/resource/schema/rti_web_integration_service.dtd">
<dds>
  <!--...-->
</dds>

We recommend including a reference to the XSD file in the XML documents; this provides stricter validation and better autocompletion than the corresponding DTD file.

4.5. XML Tags for Configuring Web Integration Service

This section describes the XML tags you can use in a Web Integration Service configuration file. The following diagram and Table 4.1 describe the top-level tags allowed within the root <dds> tag.

Figure 4.1 Top-level Tags in the Configuration File

Table 4.1 Top-level Tags in the Configuration File

Tags within <dds>	Description	Multiplicity
<qos_library>	Specifies a QoS library and profiles. The contents of the Connext DDS QoS profile file—see the “Configuring QoS with XML” chapter in the RTI Connext DDS Core Libraries User’s Manual.	0..*
<domain_library>	Specifies a domain library. That is, a set of <domain> definitions. See Section 4.5.2.	0..*
<types>	Required. Defines types that can be used by Web Integration Service. See Section 4.5.2.	1..*
<web_integration_service>	Required. Specifies a Web Integration Service configuration. See Section 4.5.1.	1..*

4.5.1. Web Integration Service

4.5.1.1. Web Integration Service Tag

A configuration file must have at least one <web_integration_service> tag; this tag is used to configure an execution of Web Integration Service.

A configuration file may contain multiple <web_integration_service> tags. When you start Web Integration Service, you can specify which <web_integration_service> tag to use to configure the service using the -cfgName command-line option.

For example:

<?xml version="1.0" encoding="UTF-8"?>
<dds>
    <web_integration_service name="default"/>
    <web_integration_service name="shapesDemoTutorial">
    <!--...-->
    </web_integration_service>
</dds>

Starting Web Integration Service with the following command will use the <web_integration_service> tag with the name default.

$NDDSHOME/bin/rtiwebintegrationservice -cfgFile file.xml -cfgName default

Because a configuration file may contain multiple <web_integration_service> tags, one file can be used to configure multiple Web Integration Service executions.

The following diagram and Table 4.2 describe the tags allowed within a <web_integration_service> tag.

Figure 4.2 Web Integration Service Tag Structure

Table 4.2 Web Integration Service Tag

Tags within <web_integration_service>	Description and Attributes	Multiplicity
<application>	Description Applications are a collection of instantiated DomainParticipants and their contained DDS entities. Attributes name: Application name. <web_integration_service name="ExampleService"> <application name="MyApplication"> <!-- ... --> </application> <!-- More application definitions ... --> </web_integration_service>	0..*

4.5.1.2. Application Tag

An <application> provides a way to organize a set of instantiated participants that belong to the same logical application. That is, it provides a namespace that client applications can leverage to categorize their DomainParticipants within a Web Integration Service instance.

When a certain Web Integration Service configuration is instantiated using the -cfgName command-line option, all of its contained applications—along with the DDS entities associated with them—are automatically instantiated as well. This also applies to the creation of new applications via Web Integration Service’s REST API, as the creation of a new application will also trigger the instantiation of all its contained DomainParticipants and entities.

Table 4.3 Application Tag

Tags within <application>	Description and Attributes	Multiplicity
<domain_participant>	Description Specifies a DomainParticipant configuration. Attributes name: DomanParticipant name. domain_ref (optional): Reference (fully qualified name) to a defined <domain> in a domain library. domain_id (optional): Domain ID. If specified, overrides the ID of the domain it refers to. If no domain_id is specified directly or in the referenced domain, then the default domain_id is 0. <application name="MyApplication"> <domain_participant name="MyParticipant" domain_ref="MyDomainLibrary::MyDomain" domain_id="32"> <!-- ... --> </domain_participant> <!-- More DomainParticipant definitions ... --> </application>	0..*

4.5.1.3. DomainParticipant Tag

A <domain_participant> is defined by specifying the set of Entities it contains. This is done using tags such as <publisher>, <subscriber>, <data_writer>, and <data_reader>, which specify an Entity of their corresponding type. These Entities are created within the DomainParticipant instantiated by the <application>, which is instantiated when the Web Integration Service configuration that contains it is created or when a new application is created by the REST API.

The <domain_participant> also specifies <register_type> and <topic>, which can be associated with a Domain where topics and their associated types are either already defined (see section on Domain Libraries) or are defined within the <domain_participant>.

Figure 4.3 DomainParticipant Tag Structure

Table 4.4 DomainParticipant Tag

Tags within <domain_participant>	Description and Attributes	Multiplicity
<register_type>	Description Registers a type within the DomainParticipant. The type definition will be instantiated when an associated Topic is created. Attributes name: Name under which the type is registered with the DomanParticipants. type_ref: Reference (fully qualified name) to a type defined within <types>. This is the type that is being registered. <domain_participant name="MyParticipant"> <register_type name="MyShapeType" type_ref="ShapeType" /> <!-- ... --> </domain_participant>	0..*
<topic>	Description Specifies a Topic configuration. Attributes name: Topic name. register_type_ref: Reference (name) to a register_type within the domain or DomainParticipant. <domain_participant name="MyParticipant"> <topic name="Square" register_type_ref="MyShapeType" /> <!-- ... --> </domain_participant>	0..*
<publisher>	Description Specifies a Publisher configuration. Attributes name: Publisher name. <domain_participant name="MyParticipant"> <publisher name="MyPublisher"> <!-- DataWriters or PublisherQos --> </publisher> <!-- ... --> </domain_participant>	0..*
<subscriber>	Description Specifies a Subscriber configuration. Attributes name: Subscriber name. <domain_participant name="MyParticipant"> <subscriber name="MySubscriber"> <!-- DataReaders or SubscriberQos --> </subscriber> <!-- ... --> </domain_participant>	0..*
<domain_participant_qos>	Description DomainParticipant QoS configuration. Attributes base_name (optional): Reference (fully qualified name) to a QoS Profile. <domain_participant base="MyParticipant"> <!-- ... --> <domain_participant_qos base="MyQosLibrary::MyQosProfile"> <!-- You may override the referenced QosProfile by defining QoS settings here. --> </domain_participant_qos> </domain_participant>	0..1

4.5.1.4. Publisher Tag

The <publisher> tag specifies a Publisher configuration. That is, it defines a set of DataWriters using the <data_writer> tag, as well as the Publisher’s QoS settings using the <publisher_qos> tag.

Web Integration Service does not support the use of implicit Publishers. Therefore, you must define DataWriters under an existing <publisher> tag in the configuration file.

Table 4.5 Publisher Tag

Tags within <publisher>	Description and Attributes	Multiplicity
<data_writer>	Description Specifies a DataWriter configuration. Attributes name: DataWriter name. topic_ref: Name of a <topic> associated with the <domain_participant>. <publisher name="MyPublisher"> <data_writer name="MySquareWriter" topic_ref="Square"> <!-- ... --> </data_writer> <!-- ... --> </publisher>	0..*
<publisher_qos>	Description Publisher QoS configuration. Attributes base_name (optional): Reference (fully qualified name) to a QoS Profile. <publisher name="MyPublisher"> <!-- ... --> <publisher_qos base_name="MyQosLibrary::MyQosProfile"> <!-- You may override the referenced QosProfile by defining QoS settings here. --> </publisher_qos> </publisher>	0..1

4.5.1.5. Subscriber Tag

The <subscriber> tag specifies a Subscriber configuration. That is, it defines a set of DataReaders using the <data_reader> tag, as well as the Subscriber’s QoS settings using the <subscriber_qos> tag.

Web Integration Service does not support the use of implicit Subscribers. Therefore, clients need to define DataReaders under an existing <subscriber> tag in the configuration file.

Table 4.6 Subscriber Tag

Tags within <subscriber>	Description and Attributes	Multiplicity
<data_reader>	Description Specifies a DataReader configuration. Attributes name: DataReader name. topic_ref: Name of a <topic> associated with the <domain_participant>. <subscriber name="MySubscriber"> <data_reader name="MySquareReader" topic_ref="Square"> <!-- ... --> </data_reader> <!-- ... --> </subscriber>	0..*
<subscriber_qos>	Description Subscriber QoS configuration. Attributes base_name (optional): Reference (fully qualified name) to a QoS Profile. <subscriber name="MySubscriber"> <!-- ... --> <subscriber_qos base_name="MyQosLibrary::MyQosProfile"> <!-- You may override the referenced QosProfile by defining QoS settings here. --> </subscriber_qos> </subscriber>	0..1

4.5.1.6. DataWriter Tag

The <data_writer> tag specifies the topic it is associated with (see Table 4.5), as well as its QoS configuration (see Table 4.7).

Table 4.7 DataWriter Tag

Tags within <data_writer>	Description and Attributes	Multiplicity
<datawriter_qos>	Description DataWriter QoS configuration. Attributes base_name (optional): Reference (fully qualified name) to a QoS Profile. <data_writer name="MySquareWriter"> <!-- ... --> <datawriter_qos base_name="MyQosLibrary::MyQosProfile"> <!-- You may override the referenced QosProfile by defining QoS settings here. --> </datawriter_qos> </data_writer>	0..1

4.5.1.7. DataReader Tag

The <data_reader> tag specifies the topic it is associated with (see Table 4.6), as well as its QoS configuration (see Table 4.8). DataReaders can also specify filter expressions that enable content filtering.

Table 4.8 DataReader Tag

Tags within <data_reader>	Description and Attributes	Multiplicity
<filter>	Description Enables the creation of the DataReader with this configuration from a ContentFilteredTopic. Attributes name: Name of the ContentFilteredTopic that will be associated with the same Topic referenced by the containing <data_reader>. filter_kind: Specifies which ContentFilter to use. It defaults to using the builtin SQL filter. For example: <data_reader name="MySquareReader"> <content_filter name="AFilter" kind="builtin.sql"> <!-- ... --> </content_filter> <!-- ... --> </data_reader>	0..1
<datareader_qos>	Description DataReader QoS configuration. Attributes base_name (optional): Reference (fully qualified name) to a QoS Profile. <data_reader name="MySquareWriter"> <!-- ... --> <datareader_qos base_name="MyQosLibrary::MyQosProfile"> <!-- You may override the referenced QosProfile by defining QoS settings here. --> </datareader_qos> </data_reader>	0..1

4.5.1.8. Filter Tag

The <filter> tag within a <data_reader> enables content filtering. It causes the corresponding DataReader to be created from a ContentFilteredTopic with the specified filter characteristics.

Table 4.9 Filter Tag

Tags within <filter>	Description and Attributes	Multiplicity
<expression>	Description Filter expression. <data_reader name="MySquareReader"> <content_filter name="AFilter" kind="builtin.sql"> <expression>x &lt; 10</expression> </content_filter> </data_reader>	0..1
<expression_parameters>	Description List of parameters. Parameters are specified using <element> tags. The maximum number of parameters is 100. <data_reader name="MySquareReader"> <content_filter name="AFilter" kind="builtin.sql"> <expression>x &lt; %0</expression> </content_filter> <expression_parameters> <element>10</element> <!-- params --> </expression_parameters> </data_reader>	0..1

For example:

<?xml version="1.0" encoding="UTF-8"?>
<dds>
    <!-- ... -->
    <web_integration_service name="ExampleConfiguration">
        <application name="MyApplication">
            <domain_participant name="MyParticipant">
                <register_type name="MyShapeType" typeRef="ShapeType"/>
                <topic name="Square"  register_type_ref="MyShapeType"/>
                <publisher name="MyPublisher">
                    <data_writer name="MySquareWriter" topic_ref="Square"/>
                </publisher>
                <subscriber name="MySubscriber">
                    <data_reader name="MySquareReader" topic_ref="Square">
                        <content_filter name="MyFilter" kind="builtin.sql">
                            <expression>x &lt; %0</expression>
                            <expression_parameters>
                                <element>10</element>
                            </expression_parameters>
                        </content_filter>
                    </data_reader>
                </subscriber>
            </domain_participant>
        </application>
    </web_integration_service>
    <!-- ... -->
</dds>

The above configuration defines a <domain_participant> that defines a Topic Square for a MyShapeType type. The DomainParticipant contains:

• A Publisher that has a DataWriter created from the Topic Square.

• A Subscriber that has a DataReader created from a ContentFilteredTopic whose related Topic, Square, uses a SQL filter.

4.5.2. Types, QoS Library, and Domain Library

The rest of tags are part of the XML-based Application Creation API for Connext DDS.

• The <types> tag is defined in the section “Creating User Data Types with Extensible Markup Language (XML)” in the RTI Connext DDS Core Libraries User’s Manual.

• The <qos_library> tag is defined in the “QoS Libraries” section of the RTI Connext DDS Core Libraries User’s Manual.

• The <domain_library> tag is defined in the “Domain Library” section of the RTI Connext DDS XML-Based Application Creation Getting Started Guide.

4.6. Authentication and Access Control Mechanisms

Web Integration Service supports a simple access-control mechanism which can be enabled to restrict access to its REST API and WebSocket API. It is based on a set of API keys that authorize client applications to perform operations over the HTTPS and Secure WebSocket protocols. When access control is enabled, client applications without an authorized API key are rejected and are not allowed to perform any operation on the running instance.

To enable access control, we recommend that you enable HTTPS/WSS to secure the transmission of API keys and data. While HTTPS/WSS can be enabled for all kinds of applications—even when access control is not a requirement—API keys should never be exchanged over simple HTTP or WebSocket, as malicious applications could extract the API key, which should be considered a secret.

Section 4.6.1 explains how to enable HTTPS/WSS in Web Integration Service. Section 4.6.2 describes the Access Control List file. Section 4.6.3 illustrates how to manage the Access Control List file. Section 4.6.4 explains how to configure client applications to use the generated API keys.

4.6.1. Enabling HTTPS/WSS

To secure the transmission of API keys and the data exchanged between client applications and Web Integration Service, information must be exchanged via HTTPS/WSS.

To enable HTTPS/WSS, all the ports specified in the -listeningPorts command-line option must add a trailing “s” to the port number and provide an SSL certificate (which must include the private key). For example:

$NDDSHOME/bin/rtiwebintegrationservice -listeningPorts 8080s \
    -sslCertificate ~/.certificates/server.pem

The trailing “s” (that is, using 8080s instead of 8080) indicates that HTTPS/WSS must be used on every port it follows. In contrast, ports specified without a trailing “s” will use HTTP/WS.

Unlike other popular web servers, Web Integration Service’s web server requires you to combine both the actual certificate and the RSA private key section in the same file.

Note

For example, Apache uses the SSLCertificateFile and SSLCertificateKeyFile parameters to configure certificates and keys. Nginx uses two different parameters: ssl_certificate and ssl_certificate_key.

Assuming the original certificate is stored in a file called server.crt and the private key is in a file called server.key, these certificates need to be combined in a common PEM file (which in this example we call server.pem) as follows:

$ cat server.crt > server.pem
$ cat server.key >> server.pem

In some cases, certificate authorities provide two different certificates, one for the domain and one for a certificate from the appropriate certificate authority (e.g., DigiCert). In that case, all certificates and keys can be combined as follows:

$ cat star_dot_example_dot_com.crt > server.pem
$ cat DigiCertCA.crt >> server.pem
$ cat star_dot_example_dot_com.key  >> server.pem

4.6.2. The Access Control List File

To enable access control, you need to provide an Access Control List (ACL) file when starting the service. The -aclFile command-line option specifies the path to the ACL file and configures the service to reject HTTP requests and WebSocket connections from clients that do not provide a valid API key (i.e., an API key included in the Access Control List file the service was started with).

If the file specified with -aclFile does not exist, Web Integration Service will create an empty file that can be populated later on with the -createAPIKey and -deleteAPIKey command-line options.

The Access Control List is a Sqlite3 database with a single table that contains all the API keys, a message describing each API key, and the date when they were added to the file.

4.6.3. Creating, Deleting, and Listing API keys

The rtiwebintegrationservice executable can be used to dynamically create, delete, and list API keys. If the file that is being updated is in use by any Web Integration Service instance, the service will be automatically notified of the changes in it. Then it will reload the list of valid API keys accordingly.

4.6.3.1. Creating API Keys

To add a new API key to an ACL file, use the -createAPIKey and -aclFile command-line options as follows:

$NDDSHOME/bin/rtiwebintegrationservice \
    -createAPIKey "API Key for ShapesDemo client" \
    -aclFile ~/.acl/acl_file.db

If the ACL file does not exist, it will automatically be created. Note that a message identifying the API key must be passed to the -createAPIKey argument.

4.6.3.2. Deleting API Keys

To delete an API key from an ACL file, use the -deleteAPIKey and -aclFile command-line options as follows:

$NDDSHOME/bin/rtiwebintegrationservice \
    -deleteAPIKey "r5x/ERs9wGkIufffeRfWSFH1li/60BUoJmJ0ETua" \
    -aclFile ~/.acl/acl_file.db

4.6.3.3. Listing API Keys

To list the API keys in an ACL file, use the -listAPIKeys and -aclFile command-line options as follows:

$NDDSHOME/bin/rtiwebintegrationservice \
    -aclFile ~/.acl/acl_file.db \
    -listAPIKeys

4.6.4. Using API Keys in Client Applications

Client applications communicating with access-control-limited instances of Web Integration Service must include a valid API key in the OMG-DDS-API-Key header field of every HTTP request and WebSocket Connection. The API key must remain secret. Therefore, clients should only share it through a secure connection and should not expose it to users of the client application.

Section 5.1 and Section 6.1 provides a complete overview of the HTTP headers and the WebSocket HELLO message involved in operations supported by Web Integration Service’s REST API and WebSocket API.