Publish / Subscribe Explained

Transcription

1 Publish / Subscribe Explained

2 Agenda! B2B P/S introduction! B2B P/S explained! Use! Subscriptions! Messages! B2B P/S important remarks and common pitfalls 2

3 NM B2B Synchronous Request/Reply Ideal for requesting snapshot information or to execute a service Publish/Subscribe Asynchronous Messaging Ideal for receiving live updates No need for frequent polling B2B External Applications R/R P/S Request Reply Subscribe Consume messages NM Publish/Subscribe NM B2B Request-Reply Message Queue 1 Message Queue 2 Message Queue 3 NM Service Layer Environment Data Management Flight Plan Management Flow and Capacity Management Historical Information Management NM Business Applications 3

4 NM P/S Introduction! What is Publish/Subscribe?! Message Exchange Pattern (MEP)! Publisher (or Producer): publishes messages on some topics! Subscriber (or Consumer): subscribes to some topics and consumes messages related to those topics.! P/S Consumer s actions:! Subscribe (Subscription Management)! Get messages (Message Consumption) 4

5 NM P/S Use HTTP B2B Client AMQP Subscription Management (SOAP R/R) Message Consumption (AMQP 1.0) NM Systems NM B2B WS Message Queue 1 Message Queue 2 Message Queue 3 NM B2B Broker 5

6 NM P/S Subscriptions! NM Subscriptions can be:! Filterable! Messages can be filtered! SubscriptionMessageFilter! Customizable! Message payload configurable! SubscriptionPayloadConfiguration 6

7 NM P/S Subscriptions! NM Subscription topics available today: AIXM_DATASETS Notification about the publication of new AIXM datasets (NM airspace data). ATM_INFORMATION Notification about newly published AIMs (ATM Information Messages). EAUP Notification about the publication of EAUPs and EUUPs. FLIGHT_DATA Notification about flight progress. FLIGHT_PLANS Notification about new flight plans and changes to existing flight plans. REGULATIONS Notification about new ATFCM regulations and changes to existing regulations. 7

8 NM P/S Messages PSMessage BusinessPSMessage TechnicalPSMessage AIMMessage SubscriptionTechnicalMessage EAUPMessage AIXMDatasetMessage RegulationMessage FlightPlanMessage Today only used for communicating state transitions FlightDataMessage 8

9 NM Subscription states Subscription State Meaning Comments ACTIVE Subscription is collecting messages PAUSED Subscription is not collecting messages User can resume it SUSPENDED Subscription is not collecting messages Only NM can unsuspend it DELETED Subscription can no longer be used 9

10 NM P/S Important remarks and common pitfalls 1. Subscription!= Queue Subscription is a means to express an interest on a given topic Queue is a container of messages on a message broker Broker is always associated to exactly one queue A B2B user can create, pause, resume and delete a subscription can be associated with more than one subscription A B2B user can connect, consume messages and disconnect from a queue 10

11 NM P/S Important remarks and common pitfalls 2. P/S Authentication! Single client certificate for R/R and P/S! But different server certificates (different URI)! B2B client Client cert. e.g. c NM B2B R/R NM B2B Broker publish.nm.eurocontrol.int Import full certificate chain, up to the root! 11

12 NM P/S Important remarks and common pitfalls 3. P/S Authorization! Subscriptions (and their associated queues) are linked to the B2B certificate that created them! Each certificate gives access to its own subscriptions (and associated queues) Queue DSNA C1 DSNA Certificate C1 Queue DSNA C2 Queue Skyguide C3 NM B2B Broker 12

13 NM P/S Important remarks and common pitfalls 4. Subscription lifetime! A subscription is meant to be created once and kept until it is no longer needed.! A subscription can be paused and resumed many times! Do not delete and recreate the same subscription over and over!!!! OK to delete and re-create a subscription to change the subscription parameters 13

14 NM P/S Important remarks and common pitfalls 5. Message TTL! All messages have a TTL after which they expire! Expired messages are permanently deleted from the queue! When a message expires from a queue, the corresponding subscription is automatically paused by NM.! A Technical Message informs about the new state with reason MSG_EXPIRED! The Technical Message also has a TTL! AMQP client connected and consuming AMQP client disconnects Message Expires; Subscription Is paused Technical Message published Technical Message expires AMQP client re-connects Queue T T Subscription Subscription is paused: MSG_EXPIRED Time Hence: upon re-connection always check the status of the subscription! 14

15 NM P/S Important remarks and common pitfalls 6. Client performance! Watch out for MSG_EXPIRED!! Ways to improve performance on message consumption! Multiple consumers AMQP Client 1 AMQP Client 2 AMQP Client 3 Broker! Multithreading AMQP Client 1 Broker Thread pool 15

16 NM P/S Recommended Workflow B2B P/S User B2B Web Services B2B Broker NM Backend Systems SubscriptionCreationRequest Connect to Queue Consume Message Create Queue Send Technical Msg Client queue; Subscription is Paused SubscriptionResumeRequest Consume Messages Activate Subscription Send Technical Msg Subscription is Active; queue accepts business messages. AMQP Receiver Link Subscription Management (SOAP R/R) P/S Messages (AMQP 1.0) 16

17 NM P/S Recommended Workflow First develop and test your P/S application and subscriptions on PREOPS PREOPS publish.preops.nm.eurocontrol.int Check for: subscription coverage, application correctness, connection problems, performance issues (MSG_EXPIRED!) Only when satisfactory create the same subscriptions on OPS OPS publish.nm.eurocontrol.int 17

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