createNode('example'); const publisher = node.createPublisher( 'std_msg/msg/String', 'topic'); setInterval(() => { publisher.publish('Hello World'); 79e1/p8_1.jpg) ## List of Features ## rclnodejs ROS node -- create/destroy ROS nodes Publisher/Subscription -- send/receive ROS message • Client/Service -- write client/service of ROS request • QoS Validation utilities -- check if it meets rules Logging -- easier debugging ## ros2-web-bridge Publisher/Subscription -- send/receive msg in browser • Client/Service -- write client/service of ROS request in

### 10. 发布者 Publisher 的编程实现 主讲人：古月 ## 话题模型  话题模型（发布/订阅） ## • 创建功能包 $ cd ~/catkin_ws/src $ catkin_create_pkg learning_topic ros::init(argc, argv, "velocity_publisher"); // 创建节点句柄 ros::NodeHandle n; // 创建一个Publisher，发布名为/turtle1/cmd_vel的topic，消息类型为geometry_msgs::Twist，队列长度 ros::Publisher turtle_vel_pub = n.adve vel_msg.angular.z); // 按照循环频率延时 loop_rate.sleep(); } return 0; } velocity_publisher.cpp ## 如何实现一个发布者 • 初始化ROS节点； - 向ROS Master注册节点信息，包括发布的话题名和话题中的消息类型； • 创建消息数据； - 按照一定频率循环发布

any contents or a part of contents of this e-book in any manner without written consent of the publisher. We strive to update the contents of our website and tutorials as timely and as precisely as possible publishReplay ..... 80 share ..... 81 catchError ..... 82 retry ..... 83 RxJS — Working with Subscription ..... 85 count() operator ..... 85 RxJS — Working with Subjects ..... 86 Create a subject with the observable i.e. the source interacts for an example button click, Http request, etc. ## Subscription When the observable is created, to execute the observable we need to subscribe to it. It can

interface{}) bool type Publisher struct { m sync.RWMutex buffer int timeout time.Duration subscribers map[subscriber]topicFunc // chan中是数据，函数判断数据是否包含 } func (p *Publisher) SubscribeTopic(topic (p *Publisher) Publish(v interface{}) { // 发布时，轮询所有注册上来的对象 for sub, topic := range p.subscribers { go p.sendTopic(sub, topic, v, wg) // 消息推送到订阅者的chan } func (p *Publisher) sendTopic(sub Warningf("stop server") grpcServer.GracefulStop() 1 type Service struct { 2 bus *pubsub.Publisher 3 proto.UnimplementedPubSubServiceServer 4 } 实现 protoBuf 定义 RPC 的接口 func (s *Service)

ros::ServiceServer command_service = n.advertiseService("/turtle_command", commandCallback); // 创建一个Publisher，发布名为/turtle1/cmd_vel的topic，消息类型为geometry_msgs::Twist，队列长度：turtle_vel_pub = n.advertise #include #include ros::Publisher turtle_vel_pub; bool pubCommand = false; // service回调函数，输入参数 req，输出参数 res bool commandCallback command state!" ## - 创建服务器代码（Python） pubCommand = False; turtle_vel_pub = rospy.Publisher('/turtle1/cmd_vel', Twist, queue_size=10) def command_thread(): while True:

Internals ..... 885 29. Logical Replication ..... 887 29.1. Publication ..... 887 29.2. Subscription ..... 888 29.3. Row Filters ..... 894 29.4. Column Lists ..... 902 29.5. Conflicts 1622 ALTER SEQUENCE ..... 1623 ALTER SERVER ..... 1626 ALTER STATISTICS ..... 1628 ALTER SUBSCRIPTION ..... 1629 ALTER SYSTEM ..... 1632 ALTER TABLE ..... 1634 ALTER TABLESPACE ..... 1654 CREATE SEQUENCE ..... 1798 CREATE SERVER ..... 1802 CREATE STATISTICS ..... 1804 CREATE SUBSCRIPTION ..... 1808 CREATE TABLE ..... 1813 CREATE TABLE AS ..... 1836 CREATE TABLESPACE ..... 1839

Internals ..... 933 29. Logical Replication ..... 934 29.1. Publication ..... 934 29.2. Subscription ..... 935 29.3. Row Filters ..... 942 29.4. Column Lists ..... 950 29.5. Conflicts .... 1707 ALTER SEQUENCE ..... 1708 ALTER SERVER ..... 1712 ALTER STATISTICS ..... 1714 ALTER SUBSCRIPTION ..... 1716 ALTER SYSTEM ..... 1720 ALTER TABLE ..... 1722 ALTER TABLESPACE ..... 1743 CREATE SEQUENCE ..... 1895 CREATE SERVER ..... 1899 CREATE STATISTICS ..... 1901 CREATE SUBSCRIPTION ..... 1905 CREATE TABLE ..... 1911 CREATE TABLE AS ..... 1935 CREATE TABLESPACE ..... 1938

Container Platform 4.14 Operator 14 警告 警告 在使用 skipRange 字段时，跳过的 Operator 版本会从更新图中删除，因此不再可以 被带有 Subscription 对象的 spec.startingCSV 属性的用户安装。 如果要为来自多个之前的版本的 Operator 版本直接（一个版本递增）更新，并保留 以前版本的安装可供用户使用，请始终使用 skipRange Registry 是一个存储了 Operator 捆绑包镜像的数据库，每个都包含所有频道的最新和历史版本。 2.3.1.14. Subscription OpenShift Container Platform 4.14 Operator 24 订阅（subscription） 通过跟踪软件包中的频道来保持 CSV 最新。 2.3.1.15. 更新 更新图表 表 更新图表将 CSV 的版本关联到一 应用程序元数据。例如：名称、版本、图标、所需资源。 第 第 2 章 章 了解 了解 OPERATOR 25 CatalogSour ce catsrc 定义应用程序的 CSV、CRD 和软件包存储库。 Subscription sub 通过跟踪软件包中的频道来保持 CSV 最新。 InstallPlan ip 为自动安装或升级 CSV 而需创建的资源的计算列表。 OperatorGro up og 将部署在同一命名空间中的所有

if they failed) ## Producers and consumers - An event is typically generated by a producer (or publisher or sender) and processed by one or multiple consumers (or subscribers or recipients) • Events are only needs to receive ack from broker ## Communication patterns (I) ## Load balancing or shared subscription - A logical producer/consumer can be implemented by multiple physical tasks running in parallel degrade. - DBs support secondary indexes for efficient search while MBs only offer topic-based subscription. - DB query results depend on a snapshot and clients are not notified if their query result changes

Internals ..... 861 31. Logical Replication ..... 863 31.1. Publication ..... 863 31.2. Subscription ..... 864 31.3. Row Filters ..... 870 31.4. Column Lists ..... 878 31.5. Conflicts 1583 ALTER SEQUENCE ..... 1584 ALTER SERVER ..... 1587 ALTER STATISTICS ..... 1589 ALTER SUBSCRIPTION ..... 1590 ALTER SYSTEM ..... 1593 ALTER TABLE ..... 1595 ALTER TABLESPACE ..... 1613 CREATE SEQUENCE ..... 1755 CREATE SERVER ..... 1759 CREATE STATISTICS ..... 1761 CREATE SUBSCRIPTION ..... 1765 CREATE TABLE ..... 1770 CREATE TABLE AS ..... 1792 CREATE TABLESPACE ..... 1795