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Fault-Tolerant Reliable Delivery of Messages in Distributed Publish/Subscribe Systems

Fault-Tolerant Reliable Delivery of Messages in Distributed Publish/Subscribe Systems. Shrideep Pallickara, Hasan Bulut & Geoffrey Fox Community Grids Lab Indiana University. Reliable Delivery: Desiderata. Cope with node/link failures & unpredictable links

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Fault-Tolerant Reliable Delivery of Messages in Distributed Publish/Subscribe Systems

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  1. Fault-Tolerant Reliable Delivery of Messages in Distributed Publish/Subscribe Systems Shrideep Pallickara, Hasan Bulut & Geoffrey Fox Community Grids Lab Indiana University

  2. Reliable Delivery: Desiderata • Cope with node/link failures & unpredictable links • Links may duplicate, garble and lose messages • Many-to-Many reliable delivery across sessions • Support recovery from failures or disconnects • Support replays • Transport-independent • Support exactly-once delivery • Order, duplicate detection • Authorized reliable delivery

  3. Reliable Delivery • One Repository associated with a reliable topic • A Repository can manage multiple reliable topics

  4. Reliable Delivery P2R-Order R2S*-Persistent S2R-ACK R2P-NAK R2S-Rectify S2R-NAK P2R-Retransmit R2P-ACK R2S-Retransmit R2S-Sync Regular Exchange Error Detection Error Correction

  5. Reliable delivery: Advantages • Reliable delivery ONLY for authorized entities • Coexists with entities not interested in reliable delivery • Storage, is not communal, and should be provisioned by the topic owner. • Control Messages are issued over different topics. • Discovery constraints can be imposed e.g. Restrict replays • Different QoS can be associated with control topics. • Require signed acknowledgements (Non-repudiation) • Buffering & Jitter reduction services for replayed messages. • Streams replayed at say 24 fps instead of 500 fps • Easy to maintain audit trails • Track client loss rates, NAKs, disconnects & recoveries • Lends itself naturally for greater redundancy

  6. Repository Redundancy

  7. Repository Redundancy • Multiple repositories constitute a repository bundle • A given repository can be part of multiple bundles • Associate a repository-bundle for a given topic for greater redundancy • Sustain repository failures and downtimes • Fine tune redundancy associated with a bundle • Graceful addition & removal of constituent repositories • Clients leverage network proximity through bundle • By choosing a closer repository, communication latencies are reduced. Retransmissions and recoveries are faster. • Repository with which a client actively interacts with is its steering repository. • Set aside repositories for recovery and replays

  8. Repository Bundle: Publisher P2R-Order Repository P2R-Retransmit P2R-Order P2R-Order R2P-ACK R2P-ACK Publisher R2P-NAK R2P-NAK Repository P2R-Retransmit P2R-Retransmit P2R-Order Repository P2R-Retransmit

  9. Repository Bundle: Subscriber S2R-ACK Repository R2S*-Persistent S2R-ACK R2S*-Persistent S2R-ACK R2S-Rectify Subscriber S2R-NAK R2S-Rectify Repository S2R-NAK R2S-Retransmit R2S-Sync R2S-Retransmit R2S-Sync S2R-ACK Repository

  10. Ongoing Activities • Repository placement schemes • Reduction of publisher & subscriber overheads • Facilitate faster recoveries and error-corrections • Dedicated repositories for use in replays • Current Deployment • eSports System – To facilitate recording, annotation and replays of multimedia stream • Release Schedule • Will be released as part of NaradaBrokering 3.0 in June 2007

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