Topic-centered discovery mechanism in lightweight DDS

Abstract

The invention discloses a topic-centered discovery mechanism in a lightweight DDS (Direct Digital Synthesizer). The mechanism comprises a local participant and a remote participant, creating a plurality of different themes in the participants, and associating a writer and / or a reader under each theme according to a QoS strategy; establishing a corresponding matching relationship between the local writer and the remote reader matched with the local writer through the associated theme and QoS strategy; and establishing a corresponding matching relationship between the local reader and the remote writer matched with the local reader through the associated theme and the QoS strategy. After receiving the data writers and the data readers notified by the remote participants, the local participants start matching between the local data readers and the remote data writers and between the local data writers and the remote data readers; and after matching is completed, the two parties perform data interaction. According to the invention, the local and remote entities are managed by taking the theme as the center, the discovery process of the DDS is simplified, and the entity matching process in the discovery process of the DDS is reduced.

Description

Technical Field

[0001] The present invention relates to a DDS middleware discovery process, and in particular to a topic-centric discovery mechanism in a lightweight DDS. Background Art

[0002] The DDS (Data Distribution Service) middleware establishes connections and enables data exchange between service publishers and subscribers through service publication and subscription. Publishers advertise their supported services within the network, allowing subscribers to retrieve the publishers corresponding to their desired services and request and use the services from them. Before data exchange can begin, publishers and subscribers must first undergo a mutual discovery process, register with each other, establish a communication channel, and enable data exchange.

[0003] The current implementation of the discovery phase involves the participation of multiple entities. Specifically, the participant entity serves as the carrier, and the data writer and reader entities serve as the operators to implement the true discovery process and complete the interaction between the final data writer and data reader. This includes not only discovery between participants, but also matching, data integration, and information preservation between each remote data reader and each local data writer, as well as matching, data integration, and information preservation between each remote data writer and each local data reader. The establishment of these entity connection relationships depends on the matching of topics and QoS (quality of service). In other words, during the discovery process, multiple entities with the same topic and QoS rules will undergo repeated data integration and information preservation, depending on the number and complexity of local and remote entities. This not only causes data redundancy but also greatly wastes computing and space resources. Summary of the Invention

[0004] To address the deficiencies in the prior art, the present invention aims to provide a topic-centric discovery mechanism in a lightweight DDS.

[0005] To achieve the purpose of the present invention, the technical solution adopted by the present invention is: A lightweight topic-centric discovery mechanism in DDS, including the following steps: (1) Local participants regularly multicast SPDP messages to the network. After receiving the SPDP messages from local participants, remote participants reply with unicast SPDP messages. (2) Local participants notify remote participants of local data writers and local data readers; remote participants notify local participants of remote data writers and remote data readers; When a local writer is created, a topic and QoS management relationship are created, and the local writer is managed according to the topic and QoS policy. When a local reader is created, a topic and QoS management relationship are created at the same time, and the local reader is managed according to the topic and QoS policy. (3) After the local participant receives the data writers and data readers notified by the remote participant, it starts matching the local data readers with the remote data writers, and the local data writers with the remote data readers; (4) After the local writer is matched with the remote reader and the local reader with the remote writer, the discovery phase is completed and the two parties interact with each other.

[0006] Furthermore, in step (1), specifically, the built-in data writer in the local participant entity sends an SPDP message to the multicast domain; after the remote participant receives the SPDP message, it replies to the SPDP message through its own built-in data reader.

[0007] Furthermore, step (2) specifically includes: The data writer of the built-in publisher and the data writer of the built-in subscriber in the local participant entity send heartbeat messages to the designated remote participants to notify the creation of the local data writer and data reader; After receiving the heartbeat message, the data reader of the built-in publisher and the data reader of the built-in subscriber in the remote participant entity reply with a confirmation message, requesting the local participant to synchronize the information of the data writer and data reader; The built-in publisher data writer, built-in subscriber data writer, and built-in message data writer in the participant entity send a data message containing data writer information and a data message containing data reader information to the specified remote participant, and send a heartbeat message again.

[0008] Furthermore, in step (3), specifically, after receiving the message, the data reader of the built-in publisher and the data reader of the built-in subscriber in the remote participant entity match with their local data readers and data writers, and reply with a confirmation message to inform the data writers and data readers of the information reception status.

[0009] Furthermore, the data matching process includes: When a local writer matches a remote reader, the corresponding topic and QoS policy combination is searched locally based on the remote reader's topic and QoS policy. If such a combination exists locally, the corresponding remote reader is managed under this combination. If such a combination does not exist locally, a corresponding combination is created and the remote reader is managed accordingly. When a local reader matches a remote writer, the corresponding topic and QoS policy combination is searched locally based on the remote writer's topic and QoS policy. If this combination exists locally, the corresponding remote writer is managed uniformly under this combination. If this combination does not exist locally, the corresponding combination is created and the remote writer is managed.

[0010] Furthermore, in step (4), the data interaction process includes: When a local writer sends data to a remote reader, the local writer locates the corresponding topic and QoS policy combination based on its topic and QoS policy. It finds a matching remote reader from the management structure of the topic and QoS policy combination. It traverses the found remote readers and sends data to them. During the process of a remote writer sending data to a local reader, the remote writer's local remote writer data space is searched based on the remote writer's identification information; in the local remote writer data space, the corresponding topic and QoS policy combination is located based on its topic and QoS policy; a matching local reader is found from the management structure of the topic and QoS policy combination; the local reader is traversed and the remote writer's data is written to the local reader's historical data cache.

[0011] After the user data is organized, the data sending function of the data writer is called through the DCPS user interface. The data writer finds a matching remote data reader based on its associated topic and QoS policy. The address information of the remote data reader is added to the data message. The data is then sent to the remote data reader through the transport layer. After the data arrives at the destination host, the local remote data writer is searched based on the source address information in the message; the remote data writer finds a matching local data reader through its associated topic and QoS policy; the local data reader writes the data to the cache; the user obtains the data received by the data reader in real time by registering for a data availability callback or a data reader receiving data callback; or reads the data in the data reader cache through a timed read operation.

[0012] A DDS middleware entity includes local participants and remote participants; the local participants include publishers and subscribers, multiple different topics are created in the local participants, and writers and / or readers are associated with each topic according to a QoS policy; the remote participants include readers and writers; remote writers and / or remote readers are associated with the local topic according to a QoS policy; A matching relationship is established between a local writer and its matching remote reader through their associated topics and QoS policies; a matching relationship is established between a local reader and its matching remote writer through their associated topics and QoS policies.

[0013] The beneficial effect of the present invention is that, compared with the existing technology, the topic-centric discovery mechanism in the lightweight DDS of the present invention arranges the discovery process and manages the discovery information by topic, reduces the process processing work such as data integration and information preservation, reduces the occupation of computing resources, and completely eliminates redundant data. It not only reduces space waste, but also reduces the management work such as information synchronization between redundant data, so that the duration and complexity of the discovery phase are greatly optimized.

[0014] The advantages of the topic-centric discovery mechanism in a lightweight DDS of the present invention are as follows: with the topic as the center, the discovery process is completed with the assistance of QoS, and the matching process between readers and writers is omitted; with the topic as the center, the matching process between entities of different topics is cancelled, and the discovery time is shortened; with the topic as the center, the isolation of local readers and writers from remote writers and readers is achieved, and the existence of the opposite end does not need to be paid attention to during the matching process; with the topic as the center, during the disconnection process, the corresponding local and remote entities do not need to be aware of each other, and operations only need to be performed in the topic and QoS combination; with the topic as the center, the data of the remote entity is stored more in its own space, and redundant storage and management are not required.

[0015] The present invention provides a topic-centric discovery mechanism in a lightweight DDS. By utilizing the association between topics and local data writers, data readers and remote data readers, and remote data writers, the local data writers and data readers are untied from the remote data readers and data writers, and local and remote entities are managed with topics as the center. This simplifies the DDS discovery process, reduces the entity matching process in the DDS discovery process, and while improving the efficiency of the discovery process, reduces the occupancy of device computing power. At the same time, it also makes the implementation of the protocol more lightweight and concise. The decoupling of the relationship between local and remote entities also makes the implementation of the protocol more flexible. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a diagram of the entity relationship of the DDS middleware; Figure 2 This is a diagram of the discovery process of the DDS middleware; Figure 3 It is a schematic diagram of the data interaction process; Figure 4 It is a schematic diagram of a specific embodiment of data matching. DETAILED DESCRIPTION

[0017] The technical solution of the present invention will be further described below in conjunction with the accompanying drawings and embodiments. The following embodiments are only used to more clearly illustrate the technical solution of the present invention and are not intended to limit the scope of protection of this application.

[0018] like Figure 1 As shown, the DDS middleware entity relationship of the present invention includes local participants and remote participants; local participants include publishers and subscribers, and multiple different topics can be created in local participants, and writers and / or readers are associated under each topic according to the QoS policy; remote participants include readers and writers; remote writers and / or remote readers are associated under local topics according to the QoS policy; a corresponding matching relationship is established between the local writer and the remote reader that matches it through their associated topics and QoS policies; a corresponding matching relationship is established between the local reader and the remote writer that matches it through their associated topics and QoS policies.

[0019] The topic-centric discovery mechanism in a lightweight DDS according to the present invention comprises the following steps: (1) Local participants regularly multicast SPDP messages to the network. After receiving the SPDP messages from local participants, remote participants reply with unicast SPDP messages. Specifically, the built-in broadcast entity (built-in data writer) in the local participant entity sends an SPDP message to the multicast domain; after the remote participant receives the SPDP message, it replies with an SPDP message through its own built-in broadcast entity, completing mutual discovery between the two participants.

[0020] (2) Local participants notify remote participants of local data writers and local data readers; remote participants notify local participants of remote data writers and remote data readers; like Figure 2 As shown in the figure, the discovery process of DDS middleware includes: The publisher broadcast entity (data writer of the built-in publisher) and subscriber broadcast entity (data writer of the built-in subscriber) in the local participant entity send heartbeat messages to the designated remote participants to notify them of the creation of the local data writer and data reader. After receiving the heartbeat message, the publisher detection entity (data reader of the built-in publisher) and subscriber detection entity (data reader of the built-in subscriber) in the remote participant entity reply with an acknowledgment (Acknack) message, requesting the local participant to synchronize the information of the data writer and data reader; The publisher broadcast entity (built-in publisher data writer), subscriber broadcast entity (built-in subscriber data writer), and participant message broadcast entity (built-in message data writer) among the participant entities send data packets (data(w)) containing data writer information and data packets (data(r)) containing data reader information to the specified remote participant, and at the same time send heartbeat packets of the three entities again.

[0021] (3) After the local participant receives the data writers and data readers notified by the remote participant, it starts matching the local data readers with the remote data writers, and the local data writers with the remote data readers; After receiving the message, the publisher detection entity (data reader of the built-in publisher) and the subscriber detection entity (data reader of the built-in subscriber) in the remote participant entity match their local data readers and data writers, and reply with an Acknack message to inform the data writers and data readers of the information reception status.

[0022] The data matching process includes: When a local writer is created, a topic and QoS management relationship are created, and the local writer is managed according to the topic and QoS policy. When a local reader is created, a topic and QoS management relationship are created at the same time, and the local reader is managed according to the topic and QoS policy. When a local writer matches a remote reader, the corresponding topic and QoS policy combination is searched locally based on the remote reader's topic and QoS policy. If such a combination exists locally, the corresponding remote reader is managed under this combination. If such a combination does not exist locally, a corresponding combination is created and the remote reader is managed accordingly. When a local reader matches a remote writer, the corresponding topic and QoS policy combination is searched locally based on the remote writer's topic and QoS policy. If this combination exists locally, the corresponding remote writer is managed uniformly under this combination. If this combination does not exist locally, the corresponding combination is created and the remote writer is managed.

[0023] (4) After the local writer is matched with the remote reader and the local reader with the remote writer, the discovery phase is completed and the two parties can interact with each other.

[0024] like Figure 3 As shown in the figure, the data interaction process includes: When a local writer sends data to a remote reader, the local writer locates the corresponding topic and QoS policy combination based on its topic and QoS policy. It finds a matching remote reader from the management structure of the topic and QoS policy combination. It traverses the found remote readers and sends data to them. During the process of a remote writer sending data to a local reader, the remote writer's local remote writer data space is searched based on the remote writer's identification information; in the local remote writer data space, the corresponding topic and QoS policy combination is located based on its topic and QoS policy; a matching local reader is found from the management structure of the topic and QoS policy combination; the local reader is traversed and the remote writer's data is written to the local reader's historical data cache.

[0025] Specifically, the DDS data interaction process includes: After user data organization is completed, the data sending function of the data writer is called through the DCPS user interface. The data writer finds a matching remote data reader based on its associated topic and QoS policy. The address information of the remote data reader is added to the data message. The data is then sent to the remote data reader through the transport layer. After the data arrives at the destination host, the local remote data writer is searched based on the source address information in the message; the remote data writer finds a matching local data reader through its associated topic and QoS policy; the local data reader writes the data to the cache; the user can obtain the data received by the data reader in real time by registering a data available callback or a data reader receiving data callback; the user can also read the data in the data reader cache through a scheduled read operation.

[0026] like Figure 4 As shown, in a specific embodiment of the present invention, the data matching process includes: The local server receives information from the remote data reader and creates an information space for the remote data reader locally. The remote reader and the local writer are matched based on the topic. Remote data reader-1 searches for the corresponding topic data based on its own topic information. After finding the corresponding topic data, it searches for the existing QoS policy in its topic data. It compares the QoS policies. If the QoS policy matches its own QoS policy, it establishes a connection between its own data and the matching QoS policy. Otherwise, it creates its own QoS policy under the topic. The matching process between remote data reader-2 and remote data reader-3 and the local writer is the same as above; The local server receives information from the remote data writer and creates an information space for the remote data writer locally. The remote writer and the local reader are matched based on the topic. Remote data writer 1 searches for the corresponding topic data based on its own topic information. After finding the corresponding topic data, it searches for the existing QoS policy in its topic data. It compares the QoS policies. If the QoS policy matches its own QoS policy, it establishes a connection between its own data and the matching QoS policy. Otherwise, it creates its own QoS policy under the topic. The matching process of remote data writer-2 and remote data writer-3 with the local reader is the same as above.

[0027] The beneficial effect of the present invention is that, compared with the existing technology, the topic-centric discovery mechanism in the lightweight DDS of the present invention arranges the discovery process and manages the discovery information by topic, reduces the process processing work such as data integration and information preservation, reduces the occupation of computing resources, and completely eliminates redundant data. It not only reduces space waste, but also reduces the management work such as information synchronization between redundant data, so that the duration and complexity of the discovery phase are greatly optimized.

[0028] The advantages of the topic-centric discovery mechanism in a lightweight DDS of the present invention are as follows: with the topic as the center, the discovery process is completed with the assistance of QoS, and the matching process between readers and writers is omitted; with the topic as the center, the matching process between entities of different topics is cancelled, and the discovery time is shortened; with the topic as the center, the isolation of local readers and writers from remote writers and readers is achieved, and the existence of the opposite end does not need to be paid attention to during the matching process; with the topic as the center, during the disconnection process, the corresponding local and remote entities do not need to be aware of each other, and operations only need to be performed in the topic and QoS combination; with the topic as the center, the data of the remote entity is stored more in its own space, and redundant storage and management are not required.

[0029] The present invention provides a topic-centric discovery mechanism in a lightweight DDS. By utilizing the association between topics and local data writers, data readers and remote data readers, and remote data writers, the local data writers and data readers are untied from the remote data readers and data writers, and local and remote entities are managed with topics as the center. This simplifies the DDS discovery process, reduces the entity matching process in the DDS discovery process, and while improving the efficiency of the discovery process, reduces the occupancy of device computing power. At the same time, it also makes the implementation of the protocol more lightweight and concise. The decoupling of the relationship between local and remote entities also makes the implementation of the protocol more flexible.

[0030] The applicant of the present invention has made a detailed explanation and description of the implementation examples of the present invention in conjunction with the drawings in the specification. However, those skilled in the art should understand that the above implementation examples are only preferred implementation plans of the present invention, and the detailed description is only to help readers better understand the spirit of the present invention, and is not a limitation on the scope of protection of the present invention. On the contrary, any improvements or modifications based on the inventive spirit of the present invention should fall within the scope of protection of the present invention.

Claims

1. A topic-centric discovery mechanism in lightweight DDS, characterized by: Including steps: (1) Local participants regularly multicast SPDP messages to the network. After receiving the SPDP messages from local participants, remote participants reply with unicast SPDP messages. (2) Local participants notify remote participants of local data writers and local data readers; remote participants notify local participants of remote data writers and remote data readers; When a local writer is created, a topic and QoS management relationship are created, and the local writer is managed according to the topic and QoS policy. When a local reader is created, a topic and QoS management relationship are created at the same time, and the local reader is managed according to the topic and QoS policy. (3) After the local participant receives the data writers and data readers notified by the remote participant, it starts matching the local data readers with the remote data writers, and the local data writers with the remote data readers; (4) After the local writer is matched with the remote reader and the local reader with the remote writer, the discovery phase is completed and the two parties interact with each other.

2. The topic-centric discovery mechanism in the lightweight DDS according to claim 1 is characterized in that: In step (1), specifically, the built-in data writer in the local participant entity sends an SPDP message to the multicast domain; after the remote participant receives the SPDP message, it replies to it with an SPDP message through its own built-in data reader.

3. The topic-centric discovery mechanism in the lightweight DDS according to claim 1 is characterized in that: Step (2) specifically includes: The data writer of the built-in publisher and the data writer of the built-in subscriber in the local participant entity send heartbeat messages to the designated remote participants to notify the creation of the local data writer and data reader; After receiving the heartbeat message, the data reader of the built-in publisher and the data reader of the built-in subscriber in the remote participant entity reply with a confirmation message, requesting the local participant to synchronize the information of the data writer and data reader; The built-in publisher data writer, built-in subscriber data writer, and built-in message data writer in the participant entity send a data message containing data writer information and a data message containing data reader information to the specified remote participant, and send a heartbeat message again.

4. The topic-centric discovery mechanism in the lightweight DDS according to claim 1 is characterized in that: In step (3), specifically, after receiving the message, the data reader of the built-in publisher and the data reader of the built-in subscriber in the remote participant entity match with their local data readers and data writers, and reply with a confirmation message to inform the data writers and data readers of the information reception status.

5. The topic-centric discovery mechanism in the lightweight DDS according to claim 4 is characterized in that: The data matching process includes: When a local writer matches a remote reader, the corresponding topic and QoS policy combination is searched locally based on the remote reader's topic and QoS policy. If such a combination exists locally, the corresponding remote reader is managed under this combination. If such a combination does not exist locally, a corresponding combination is created and the remote reader is managed accordingly. When a local reader matches a remote writer, the corresponding topic and QoS policy combination is searched locally based on the remote writer's topic and QoS policy. If this combination exists locally, the corresponding remote writer is managed uniformly under this combination. If this combination does not exist locally, the corresponding combination is created and the remote writer is managed.

6. The topic-centric discovery mechanism in the lightweight DDS according to claim 1, characterized in that: In step (4), the data interaction process includes: When a local writer sends data to a remote reader, the local writer locates the corresponding topic and QoS policy combination based on its topic and QoS policy. It finds a matching remote reader from the management structure of the topic and QoS policy combination. It traverses the found remote readers and sends data to them. During the process of a remote writer sending data to a local reader, the remote writer's local remote writer data space is searched based on the remote writer's identification information; in the local remote writer data space, the corresponding topic and QoS policy combination is located based on its topic and QoS policy; a matching local reader is found from the management structure of the topic and QoS policy combination; the local reader is traversed and the remote writer's data is written to the local reader's historical data cache.

7. The topic-centric discovery mechanism in the lightweight DDS according to claim 6, characterized in that: After user data organization is completed, the data sending function of the data writer is called through the DCPS user interface. The data writer finds a matching remote data reader based on its associated topic and QoS policy, and adds the remote data reader's address information to the data message. Send data to remote data readers through the transport layer; After the data arrives at the destination host, it searches for the local remote data writer based on the source address information in the message. The remote data writer finds the matching local data reader based on its associated topic and QoS policy. The local data reader writes the data into the cache; Users can obtain data received by the data reader in real time by registering the data available callback or the data reader receiving data callback; or read the data in the data reader cache through the scheduled read operation.

8. A DDS middleware entity, characterized in that: It includes local participants and remote participants. Local participants include publishers and subscribers. Multiple different topics are created in local participants. Writers and / or readers are associated with each topic according to the QoS policy. Remote participants include readers and writers. Local topics are associated with remote writers and / or remote readers according to the QoS policy. A matching relationship is established between a local writer and its matching remote reader through their associated topics and QoS policies; a matching relationship is established between a local reader and its matching remote writer through their associated topics and QoS policies.

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