Distributed Eventing in OSGi - Carsten Ziegeler
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Distributed Eventing in OSGi - Carsten Ziegeler

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OSGi Community Event 2013 (http://www.osgi.org/CommunityEvent2013/Schedule) ...

OSGi Community Event 2013 (http://www.osgi.org/CommunityEvent2013/Schedule)

ABSTRACT
One of the major topics the OSGi alliance is working on is a proposal for distributed eventing especially in the cloud. This session starts with an overview of the current state in the alliance and then shows already available solutions from the Apache Sling open source project. This includes distributing events through event admin and controlled processing of events by exactly one processor in distributed installations. The current implementations will be set in context to the ongoing activations in the alliance.

SPEAKER BIO
Carsten Ziegeler is senior developer at Adobe Research Switzerland and spends most of his time on architectural and infrastructure topics. Working for over 25 years in open source projects, Carsten is a member of the Apache Software Foundation and heavily participates in several Apache communities including Sling, Felix and ACE. He is a frequent speaker on technology and open source conferences and participates in the OSGi Core Platform and Enterprise expert groups.

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Distributed Eventing in OSGi - Carsten Ziegeler Distributed Eventing in OSGi - Carsten Ziegeler Presentation Transcript

  • Distributed Eventing in OSGi Carsten Ziegeler | Adobe Research Switzerland 1
  • About cziegeler@adobe.com @cziegeler §  RnD Team at Adobe Research Switzerland §  OSGi Core Platform and Enterprise Expert Groups §  Member of the ASF §  Most active in Apache Sling, Felix, ACE §  Conference Speaker §  Technical Reviewer §  Article/Book Author 2
  • Topics §  OSGi Event Admin §  RFP 158 – Distributed Eventing §  Apache Sling Eventing Part I §  Apache Sling Topology §  RFC 183 – Cloud Ecosystems §  Apache Sling Eventing Part II 3
  • OSGi Event Admin 4
  • OSGi Event Admin Publish Subscribe Model Component Y Component A publish OSGi Event Admin deliver Component X 5
  • OSGi Event Admin Publish Subscribe Model §  OSGi event is a data object with §  §  §  Topic (hierarchical namespace) Properties (key-value-pairs) Resource Event §  Topic: org/apache/sling/api/resource/Resource/ADDED §  Properties: path, resource type etc. 6
  • OSGi Event Admin Publish Subscribe Model §  Publisher creates event object §  Sends event through EventAdmin service §  Either synchronous or asynchronous delivery 7
  • OSGi Event Admin Publish Subscribe Model §  Publisher creates event object §  Sends event through EventAdmin service §  Either synchronous or asynchronous delivery @Component public class EventSender { @Reference private EventAdmin eventAdmin; public void run() { while ( true ) { final Map<String, Object> properties = new HashMap<String, Object>(); properties.put("timestamp", System.currentTimeMillis()); final Event event = new Event("i/am/still/alive", properties); eventAdmin.sendEvent(event); // eventAdmin.postEvent(event); Thread.sleep(2000); } } } 8
  • OSGi Event Admin Publish Subscribe Model §  Subscriber is an OSGi service (EventHandler) §  Whiteboard pattern §  Service registration properties §  Interested topic(s) §  §  org/apache/sling/api/resource/Resource/* Additional filters (optional) §  (path=/libs/*) 9
  • OSGi Event Admin Publish Subscribe Model §  Subscriber is an OSGi service (EventHandler) §  Whiteboard pattern §  Service registration properties @Component @Service(value=EventHandler.class) @Properties({ @Property(name=EventConstants.EVENT_TOPIC, value="i/am/still/alive") }) public class EventReceiver implements EventHandler { public void handleEvent(final Event event) { System.out.println("Still alive at " + event.getProperty("timestamp")); } } 10
  • OSGi Event Admin Publish Subscribe Model §  Immediate delivery to available subscribers §  No guarantee of delivery §  No distributed delivery 11
  • OSGi Event Admin Publish Subscribe Model Apache Sling Discovery Distributed Eventing Job Handling OSGi RFP 158 §  Immediate delivery to available subscribers §  No guarantee of delivery §  No distributed delivery 12
  • RFP 158 – Distributed Eventing 13
  • RFP 158 – Distributed Eventing §  Asynchronous remote eventing §  One-to-one, one-to-many §  Messages with replies §  Advertising and selection of Quality of Service §  Sender identification §  Language agnostic 14
  • Apache Sling Distributed Event Admin 15
  • Distributed OSGi Events §  Apache Sling Eventing leverages OSGi Event Admin §  Listener for all OSGi events with §  §  event property "event.distribute=true” Events are distributed §  Event property "event.application” contains the origin 16
  • Distributed OSGi Events §  Apache Sling Eventing leverages OSGi Event Admin @Component public class EventSender { @Reference private EventAdmin eventAdmin; public void send() { final Map<String, Object> properties = new HashMap<String, Object>(); properties.put("event.distribute", Boolean.TRUE); properties.put("timestamp", System.currentTimeMillis()); final Event event = new Event("i/am/still/alive", properties); eventAdmin.sendEvent(event); } } 17
  • Distributed OSGi Events §  Apache Sling Eventing leverages OSGi Event Admin @Component @Service(value=EventHandler.class) @Properties({ @Property(name=EventConstants.EVENT_TOPIC, value="i/am/still/alive") }) public class EventReceiver implements EventHandler { public void handleEvent(final Event event) { System.out.println("Still alive " + event.getProperty("event.application") + " : " + event.getProperty("timestamp")); } } 18
  • Distributed OSGi Events §  Apache Sling Eventing leverages OSGi Event Admin §  Sender controls distribution §  Apache Sling used for distribution §  §  (through JCR content repository, Apache Jackrabbit) API is independent from implementation 19
  • Apache Sling - Discovery Topologies 20
  • Installation Scenarios Single Instance Instance 1 21 Instance 2 Instance 3
  • Topologies I Apache Sling Discovery §  Instance: Unique Id (Sling ID) Single Instance ID : 1 Instance 1 ID : A 22 Instance 2 ID : X Instance 3 ID : 42
  • Topologies I Apache Sling Discovery §  Instance: Unique Id (Sling ID) §  Cluster: Unique Id and leader Single Instance Instance 1 Instance 2 Instance 3 Leader ID : 1 Leader ID : A Cluster 35 ID : X Cluster 99 23 ID : 42
  • Topologies I Apache Sling Discovery Topology: Set of clusters §  Topology Topology Single Instance Instance 1 Instance 2 Instance 3 Leader ID : 1 Leader ID : A Cluster 35 ID : X Cluster 99 24 ID : 42
  • Topologies I Apache Sling Discovery §  Topology: Set of clusters Topology Single Instance Instance 1 Instance 2 Instance 3 Leader ID : 1 Cluster 35 Leader ID : A Cluster 99 25 ID : X ID : 42
  • Topologies II Apache Sling Discovery §  Instance §  Sling ID §  Topology Optional: Name and description §  Lead er ID : 42 Belongs to a cluster §  §  Instance 3 Might be the cluster leader Additional distributed properties §  Extensible through own services (PropertyProvider) §  E.g. data center, region or enabled job topics 26 Cluster 99
  • Topologies II Apache Sling Discovery §  Cluster §  Elects (stable) leader §  Topology Stable instance ordering Instance 3 Lead er ID : 42 Cluster 99 27
  • Topologies II Apache Sling Discovery §  TopologyEventListener Topology §  Whiteboard pattern §  Receives events on topology changes §  Topology is changing §  Lead er ID : 42 Topology changed §  Instance 3 Properties changed Cluster 99 28
  • RFC 183 – Cloud Ecosystems §  “Distributed” FrameworkNodeStatus services §  Information about each cloud node §  Defined instance properties §  Extensible 29
  • RFC 183 – Cloud Ecosystems §  “Distributed” FrameworkNodeStatus services §  Information about each cloud node §  Defined instance properties §  Extensible §  Similar to Apache Sling’s topology §  Well defined services vs. listener and data objects §  One can implement the other J 30
  • From Events to Jobs 31
  • Job Handling I Apache Sling Job Handling §  Job : Guaranteed processing, exactly once §  §  Exactly one job consumer Started by client code §  §  §  Job topic Payload is a serializable map API is similar to OSGi Event Admin 32
  • Starting / Processing a Job I Apache Sling Job Handling Starting a job public interface JobManager { Job addJob(String topic, Map<String, Object> properties); … } 33
  • Starting / Processing a Job I Apache Sling Job Handling Processing a job public interface JobConsumer { String PROPERTY_TOPICS = "job.topics"; enum JobResult { OK, FAILED, CANCEL, ASYNC } JobResult process(Job job); } 34
  • Job Handling I Apache Sling Job Handling §  Sling Job Manager handles and distributes jobs §  §  …and waits for response §  §  Delivers job to a job consumer… Retry and failover Notification listeners (fail, retry, success) 35
  • Starting / Processing a Job II Apache Sling Job Handling @Component @Service(value={JobConsumer.class}) @Property(name=JobConsumer.PROPERTY_TOPICS, value="org/apache/sling/jobs/backup") public class BackupJobConsumer implements JobConsumer { @Override public JobResult process(final Job job) { // do backup return JobResult.OK; } } 36
  • Job Handling Apache Sling Job Handling §  Distributed job processing within a topology §  Instances might have different capabilities §  Offloading of heavy jobs §  Various queue configurations §  Failover handling §  Topology changes §  Progress tracking §  History of jobs 37
  • Topics §  OSGi Event Admin §  RFP 158 – Distributed Eventing §  Apache Sling Eventing Part I §  Apache Sling Topology §  RFC 183 – Cloud Ecosystems §  Apache Sling Eventing Part II 38