IBM WebSphere MQ: Using Publish/Subscribe in an MQ Network
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The document provides an overview of using IBM MQ's publish/subscribe capabilities within an MQ network, detailing the fundamentals of configurations, hierarchies, and cluster management. It explains the dynamics of subscription propagation and routing modes, comparing direct and topic host routing. Additionally, the material highlights practical scenarios for implementing publish/subscribe topologies tailored to different organizational needs and infrastructure layouts.
IBM WebSphere MQ: Using Publish/Subscribe in an MQ Network
- 1. A16: Using IBM MQ Publish/Subscribe in an MQ network David Ware, IBM © 2014 IBM Corporation
- 2. © 2014 IBM Corporation 2 Please Note IBM’s statements regarding its plans, directions, and intent are subject to change or withdrawal without notice at IBM’s sole discretion. Information regarding potential future products is intended to outline our general product direction and it should not be relied on in making a purchasing decision. The information mentioned regarding potential future products is not a commitment, promise, or legal obligation to deliver any material, code or functionality. Information about potential future products may not be incorporated into any contract. The development, release, and timing of any future features or functionality described for our products remains at our sole discretion Performance is based on measurements and projections using standard IBM benchmarks in a controlled environment. The actual throughput or performance that any user will experience will vary depending upon many factors, including considerations such as the amount of multiprogramming in the user’s job stream, the I/O configuration, the storage configuration, and the workload processed. Therefore, no assurance can be given that an individual user will achieve results similar to those stated here.
- 3. © 2014 IBM Corporation 3 Agenda The basics The possibilities Compare and contrast Scenarios
- 4. Distributed publish/subscribe And we know how everything revolves around the topic tree, dynamically built up in a queue manager QMgr QMgr Topics Subscription Subscription © 2014 IBM Corporation 7 Publisher Subscription Subscription
- 5. QMgSrubscription QMgr Topics © 2014 IBM Corporation 8 Publisher QQMMggrr Topics Subscription Publisher Subscription Subscription Distributed publish/subscribe And we know how everything revolves around the topic tree, dynamically built up in a queue manager Queue managers can work together to share their topic tree knowledge between them CHANNEL CHANNEL
- 6. CHANNEL CHANNEL © 2014 IBM Corporation 9 QQMMggrr Topics Publisher QQMMggrr Topics Subscription QQMMggrr Topics Subscription Subscription Distributed publish/subscribe And we know how everything revolves around the topic tree, dynamically built up in a queue manager Queue managers can work together to share their topic tree knowledge between them Enabling publications to be propagated to subscriptions on different queue managers The applications stay the same, the changes are at the configuration level. Subscription
- 7. Distributed publish/subscribe topologies Publish/subscribe topologies can either be created as a defined hierarchy or more dynamically as a cluster In both cases, publish/subscribe configuration is required… © 2014 IBM Corporation 10 Subscription Publisher Subscription Subscription Publisher Subscription Subscription Subscription
- 8. © 2014 IBM Corporation 11 Configuring
- 9. © 2014 IBM Corporation 12 Hierarchies Hierarchies have been supported since the original WebSphere MQ publish/subscribe broker support. Every queue manager defines its parent in the hierarchy. (except for the root queue manager) ALTER QMGR PARENT(QMGR1) Each pair of directly related queue managers must be able to connect to each other using WebSphere MQ channels. Manual channels, with queue manager named transmission queues or queue manager aliases. They are both in the same cluster. Use DISPLAY PUBSUB to check the relationships By default all subscription knowledge is shared across the hierarchy. No requirement to define administered topic objects or modify applications. Controlled by scoping down topics. Subscription Scope and Publication Scope.
- 10. Publish/Subscribe Clusters No additional connectivity configuration is required (that’s handled by the cluster) By default, no subscription knowledge is shared between members of a cluster. Meaning no publications automatically flow between queue managers. Enabling distributed pub/sub in a cluster is initially achieved by clustering an administered topic definition on one of the queue managers in the cluster. Set the cluster name to the name of the cluster. DEFINE TOPIC(FRUIT) TOPICSTR(‘/Price/Fruit’) CLUSTER(CLUSTER1) Every queue manager in the cluster automatically becomes aware of the clustered topic and shares subscription knowledge for any topic strings within that branch of the topic tree. Publications for those topic strings will now be propagated to the queue managers in the cluster with matching subscriptions. No application changes are required. FRUIT TOPICSTR(‘/Price/Fruit’) © 2014 IBM Corporation 14 Price Fruit Apples Oranges Publisher Subscription Subscription Subscription
- 11. © 2014 IBM Corporation 16 Clusters Publish/subscribe in clusters now has two modes of routing publications. DIRECT: Publications are sent directly from the publisher’s queue manager to every queue manager in the cluster with a matching subscription. TOPIC HOST: Publications are routed via one or more queue managers in the cluster. These are the queue managers where the clustered topic definitions were defined. DEFINE TOPIC … CLUSTER(…) CLROUTE(DIRECT|TOPICHOST) Publisher Subscription Subscription Subscription Publisher Subscription Subscription Subscription V8 FRUIT
- 12. © 2014 IBM Corporation 18 Which is best? Should I use a hierarchy, a direct or a topic host cluster topic? It depends… Many factors will influence the design of a pub/sub topology: Number of queue managers in the topology Size and shape of those queue managers Their capacity, availability, lifetime, interconnectivity… Number and lifetime of subscriptions Number and lifetime of individual topic strings Publication traffic Distribution pattern of publications to subscribers … One size does not fit all. First, you need to understand more about how it works…
- 13. © 2014 IBM Corporation 19 The mechanics
- 14. How it works: subscription propagation A subscription for a topic string is created on a queue manager. That queue manager tells others that it is interested in that topic string. Those queue managers register proxy subscriptions to represent the interest. On a queue manager, when a message is published to the topic string, a copy of the message is sent, over WebSphere MQ channels, to each queue manager that a proxy subscription is held for. The receiving queue manager processes the message and gives a copy to each CHANNEL © 2014 IBM Corporation 20 QQMMggrr Topics QQMMggrr Topics Subscription /Prices/Fruit/Apples subscription it holds (including any proxies…). Additional subscriptions on the same topic string do not require additional proxy subscriptions to be flowed. Proxy Subscription /Prices/Fruit/Apples Publisher /Prices/Fruit/Apples Subscription /Prices/Fruit/Apples
- 15. How it works: in a hierarchy Proxy subscriptions are sent from a queue manager to every directly connected queue Proxy Proxy © 2014 IBM Corporation 22 manager in the hierarchy. They in turn send proxy subscriptions onto any further relations. Until everyone in the hierarchy is aware of the topic string being subscribed to. Publications are then sent back down the path of proxy subscriptions. Publisher Subscription Proxy PPrrooxxyy Subscription Proxy Proxy
- 16. How it works: Direct routed clustered topics Proxy subscriptions are sent from a subscribing queue manager directly to every other queue manager in the cluster. Every queue manager becomes aware of everyone else in the cluster. Any publication from a queue manager is sent directly to those queue managers which FRUIT © 2014 IBM Corporation 23 sent proxy subscriptions. Publisher Subscription PPPPPrrrrroooooxxxxxyyyyy Subscription PPPPPrrrrroooooxxxxxyyyyy
- 17. How it works: Topic host routed clustered topics Proxy subscriptions are sent from a subscribing queue manager only to queue managers that host a definition of the clustered topic. Only the topic hosts are aware of everyone else. Any publication from a queue manager is always sent to one of the topic hosts, who then forwards the message to any subscribing queue managers. Publisher © 2014 IBM Corporation 24 Subscription Subscription V8 FRUIT Proxy Proxy
- 18. © 2014 IBM Corporation 25 Side-by-side
- 19. © 2014 IBM Corporation 26 Side-by-side: scaling Channel connectivity is restricted in both topic host routed clusters and hierarchies. Direct routed clusters will result in many queue manager channels being established, even to queue managers with no publishers or subscribers. This can be a concern for large clusters. Hierarchies and direct routed clusters share subscription knowledge across all queue managers. Subscription Publisher Subscription Publisher Subscription Subscription Publisher Subscription Subscription Topic Hierarchy Direct Cluster Topic host cluster
- 20. Side-by-side: publication flows Direct routed clusters ensure publications take the shortest path between publishers and © 2014 IBM Corporation 27 subscribers. Topic host routed clusters can introduce an additional hop, with hierarchies relying on even more. In both of these, careful placing of subscribers and publishers can achieve the same single-hop route that direct clusters provides. Subscription Publisher Subscription Publisher Subscription Subscription Subscription Publisher Subscription Hierarchy:1,2,3… hops Direct Cluster: 1 hop Topic Topic host cluster: 1 or 2 hops
- 21. Side-by-side: configuration Hierarchies require fine grain planning and configuration of queue managers. Harder to alter the hierarchical structure. Clusters allow queue managers to join and leave without too much consideration once the overall plan is defined. Careful planning of topic host routers is required. © 2014 IBM Corporation 28 Subscription Publisher Subscription Publisher Subscription Subscription Publisher Subscription Subscription Topic Hierarchy Direct Cluster Topic host cluster
- 22. Side-by-side: availability An unavailable queue manager in a hierarchy can cut off many others. In a direct routed cluster it’ll only affect the subscribers and publishers on that queue manager. In a topic host routed cluster it can affect more if the queue manager hosts a topic definition. © 2014 IBM Corporation 29 But this can be avoided… Subscription Publisher Subscription Publisher Subscription Subscription Publisher Subscription Subscription Topic Hierarchy Direct Cluster Topic host cluster
- 23. Side-by-side: availability An unavailable queue manager in a hierarchy can cut off many others. In a direct routed cluster it’ll only affect the subscribers and publishers on that queue © 2014 IBM Corporation 30 Publisher Subscription Subscription Topic Topic host cluster Subscription Publisher Subscription Publisher Subscription Subscription Hierarchy Direct Cluster manager. In a topic host routed cluster it can affect more if the queue manager hosts topics, but this can be avoided…
- 24. VEG TOPICSTR(‘/Price/Vegetables’) © 2014 IBM Corporation 31 Topic host routing Multiple queue managers can host the same clustered topic. With the same name, topic string, etc. Publications are routed based on availability and workload balancing. This increases availability and scalability of routes. Multiple topic hosts for a topic enable workload balancing of publication traffic. Publications will no longer maintain their relative order. Alternatively, hosting different topics on different queue managers can also be used to increase availability and scaling. Publisher Subscription Proxy Subscription Proxy FRUIT FRUIT Proxy Proxy FRUIT TOPICSTR(‘/Price/Fruit’) Price Fruit Apples Oranges Vegetables Potatoes VEG
- 25. Putting it into practice © 2014 IBM Corporation 33
- 26. A couple of dozen queue managers. Administratively created subscriptions for each major application, perhaps a hundred, with different topics, rarely changing. Publishers and subscriptions spread across most of the queue managers. The simplest to create is a cluster with direct routed topics. © 2014 IBM Corporation 34 ‘A bit of pub/sub’ Topic
- 27. A big ‘hub and spoke’ cluster A thousand queue managers, all talking to a few in HQ, but rarely to each other. Each with its own subscriptions and publishers. © 2014 IBM Corporation 35 Do not use a direct cluster topic!
- 28. A big ‘hub and spoke’ cluster A thousand queue managers, all talking to a few in HQ, but rarely to each other. Each with its own subscriptions and publishers. Use topic host routed clustered topics, possibly on a dedicated set of routing queue © 2014 IBM Corporation 36 managers, sized to take the load.
- 29. A small amount of pub/sub within a much larger cluster An existing single cluster containing hundreds or thousands of queue managers. Each connected to a few others in the cluster, as required. A few applications need to support inter queue manager pub/sub on a handful of queue © 2014 IBM Corporation 37 managers. It is best not to create a direct routed clustered topic in that cluster. This would result in all queue managers learning and potentially connecting of each other.
- 30. A small amount of pub/sub within a much larger cluster One solution is to create a dedicated overlaid cluster for the queue managers requiring publish/subscribe and clustering a direct topic. Optionally use PSCLUS to prevent clustered topic definitions being created in the wider cluster. The key is to set it on the full repositories © 2014 IBM Corporation 38 V7.1
- 31. A small amount of pub/sub within a much larger cluster Alternatively, create a hierarchy and don’t cluster the topic Use PSCLUS to prevent clustered topic definitions being created V7.1 © 2014 IBM Corporation 39
- 32. A small amount of pub/sub within a much larger cluster Or use a topic host routed clustered topic. All queue managers become aware of the topic but only those using it will communicate with the topic host queue manager(s). The topic hosting queue managers may need to communicate with all other queue managers under certain error circumstances. © 2014 IBM Corporation 40
- 33. A very dynamic setup © 2014 IBM Corporation 41
- 34. A very dynamic setup Thousands of loosely connected dynamic subscriptions, on thousands of different topic strings, continually coming and going, along with corresponding publishers. A few queue managers to provide availability and subscription load sharing. This introduces a special problem…. © 2014 IBM Corporation 42 Proxy subscription ‘churn’
- 35. Setting proxy subscription to force generates a wildcarded proxy subscription on all queue managers where that topic is seen. All queue managers when in a cluster. Only the queue manager where it is defined when in a hierarchy. Once that is in place there is not a need for individual proxy subscriptions for any sub-topic string. This is automatic in WebSphere MQ V8, but requires intervention prior to this Every publication is sent to every queue manager and onto the subscriptions. If no local subscriptions exist for a publication, it is simply discarded. © 2014 IBM Corporation 43 Publication broadcast /Orders/# /Orders/# /Orders/# /Orders/# /Orders/# /Orders/# V8 TOPIC TOPICSTR(‘/Orders’) PROXYSUB(FORCE)
- 36. Subscription availability © 2014 IBM Corporation 46
- 37. The continuously available point-to-point application When we need a point-to-point application to be continuously available we can cluster Requestor App © 2014 IBM Corporation 47 and duplicate its request queue. How do we get the same with a publish/subscribe application?....
- 38. The continuously available subscription The aim is to configure the system so that an application that processes publications can run multiple instances, across multiple queue managers. The instinct is to cluster the topic and duplicate the subscription. App Publisher This is not the solution, it will lead to multiple copies of each publication © 2014 IBM Corporation 48 App TOPIC CLUSTER(CLUSTER1) Subscription Subscription
- 39. The continuously available subscription Don’t define the topic as clustered (this is really important). Configure matching clustered queues, as for point-to-point and open these point-to-point App Publisher Subscription Subscription © 2014 IBM Corporation 49 queues instead of subscribing. Define the same subscription on every queue manager where a publisher can connect. Point those subscriptions at the cluster queue, leaving the target queue manager blank. App Publisher Publish to the topic, and consume from the queues… Publisher Subscription
- 40. © 2014 IBM Corporation 50 Hints and tips
- 41. © 2014 IBM Corporation 51 Problem determination Double check your configuration. When in a cluster, check each queue manager’s cluster knowledge. In V8 check the cluster state When in a hierarchy, check your relationships. Check the error logs. Check your channels. Check your proxy subscriptions. Check your topic status. Watch for publication movement. Look for a build up of messages.
- 42. © 2014 IBM Corporation 56 Summary The basics The possibilities Compare and contrast Scenarios
- 43. © 2014 IBM Corporation 57 Questions & Answers
- 44. © 2014 IBM Corporation 58 For Additional Information IBM Training http://www.ibm.com/training IBM WebSphere http://www-01.ibm.com/software/be/websphere/ IBM developerWorks www.ibm.com/developerworks/websphere/websphere2.html WebSphere forums and community www.ibm.com/developerworks/websphere/community/ 58
- 45. Legal Disclaimer • © IBM Corporation 2014. All Rights Reserved. • The information contained in this publication is provided for informational purposes only. While efforts were made to verify the completeness and accuracy of the information contained in this publication, it is provided AS IS without warranty of any kind, express or implied. In addition, this information is based on IBM’s current product plans and strategy, which are subject to change by IBM without notice. IBM shall not be responsible for any damages arising out of the use of, or otherwise related to, this publication or any other materials. Nothing contained in this publication is intended to, nor shall have the effect of, creating any warranties or representations from IBM or its suppliers or licensors, or altering the terms and conditions of the applicable license agreement governing the use of IBM software. • References in this presentation to IBM products, programs, or services do not imply that they will be available in all countries in which IBM operates. Product release dates and/or capabilities referenced in this presentation may change at any time at IBM’s sole discretion based on market opportunities or other factors, and are not intended to be a commitment to future product or feature availability in any way. Nothing contained in these materials is intended to, nor shall have the effect of, stating or implying that any activities undertaken by you will result in any specific sales, revenue growth or other results. • All customer examples described are presented as illustrations of how those customers have used IBM products and the results they may have achieved. Actual environmental costs and performance characteristics may vary by customer. © 2014 IBM Corporation 59