CS 603 Distributed Transactions

CS 603 Distributed Transactions

CS 603 Distributed Transactions February 18, 2002 What is a Transaction? Atomic The external view is that either everything in the transaction happened, or nothing did Consistent If the start state is valid, the end state is valid Isolated A transaction in process is not affected by and does not affect any other transaction

Durable Once complete, the effects of a transaction are permanent, even in the event of failure. Distributed Transactions What is the difference with Distributed Transactions? NOTHING! Must still support ACID properties Important for all the same reasons Why do we study Distributed Transactions? Some properties harder to implement Basic single-system techniques not sufficient What is a Distributed Transaction?

Data Data Transaction component Transaction component Transaction component Transaction component Data Data

Why are Distributed Transactions Hard? Atomic Different parts of a transaction may be at different sites How do we ensure all or none committed? Consistent Failure may affect only part of transaction Isolated Commitment must occur simultaneously at all sites Durable

Not much different when other problems solved Makes delayed commit difficult Key Issues Commitment Standard techniques preserve properties when commit occurs Distributed systems need commit protocols so we know when commit has occurred Failures Standard techniques support durability for commit/abort What happens if a site fails during commitment? Committing a Distributed Transaction Data

Data log Transaction component Transaction component log log Transaction component Transaction

component log Data Data Two-Phase Commit (Lamport 76, Gray 79) Assumes central coordinator Coordinator initiates protocol Participants: entities with actions to be committed/aborted Phase 1: Coordinator asks if participants can commit Participants respond yes/no

Phase 2: If all votes yes, coordinator sends Commit Otherwise send Abort Participants send Have Committed / Have Aborted Two-Phase Commit Data log Transaction CanCommit? CanCommit? Transaction component component Commit Commit Done Done

Yes Yes Coordinator Yes log Data Done Commit Transaction component CanCommit? Data Yes Done Commit

Transaction CanCommit? component Data log log Two-Phase Commit: Fault Tolerance Participant fails in Phase 1: Coordinator doesnt get unanimous yes Abort Participant fails in Phase 2: On reawakening, can ask coordinator if it should commit or abort Requires that both commit and abort states be

durable before sending yes vote Two-Phase Commit: Problems Blocks on failure Timeout before abort if participant fails All participants must wait for recovery if coordinator fails While blocked, transaction must remain Isolated Hold locks on data items touched Prevents other transactions from completing Solution: Wednesday

Recently Viewed Presentations

  • Canadian Landforms and Ecosystems

    Canadian Landforms and Ecosystems

    Canadian Landforms and Ecosystems ... Weather and climate… Compare Landforms to Ecosystems Landforms dictate types of Ecosystems. Consider what type of ecosystem is in the western Cordilla. Or consider the ecosystem in the Canadian Shield. The ecosystems in the Arctic...
  • It's a Mystery

    It's a Mystery

    Over the next hundred years, many mystery authors made their mark in literature: Sir Arthur Conan Doyle, G.K. Chesterton, Mary Roberts Rinehart, Agatha Christie, Dorothy Sayers, Ellery Queen, John Dickson Carr, and Dashiell Hammett
  • Dynamics - Weebly

    Dynamics - Weebly

    Dynamics. Dynamics is the study of why things move.. Dynamics focuses on the . forces. that cause objects to change their state of motion (e.g. Speed up/Slow down/change direction - accelerate)
  • Developing an Inner-Core SST Cooling Parameter for use

    Developing an Inner-Core SST Cooling Parameter for use

    Developing an Inner-Core SST Cooling Parameter for use in SHIPS Principal Investigator: Joseph J. Cione NOAA's Hurricane Research Division Co-Investigators: John Kaplan (HRD); Chelle Gentemann (Remote Sensing Systems); Mark Demaria (NESDIS)
  • Geolocation in USA

    Geolocation in USA

    The sensing maps were based off the F(50, 50) curves... "The Geo-location model is flawed in the sense that ITU curves and the reality on the ground do not match. You may need sensing to develop a incremental model of...
  • The Affective Domain - PROF. JONES

    The Affective Domain - PROF. JONES

    Debilitative - when anxiety hurts you. Facilitative - when anxiety helps you. Kinds of Anxiety: Communication and thought disruption. Fear of peers. Test anxiety. Extroversion and Introversion. Extroversion. Extroverted Person. Receives happiness and stress relief .
  • How to Pay Your Bill - Messiah College

    How to Pay Your Bill - Messiah College

    Click "View" or "Download" to open current billing invoice. Step 2: View Your Bill. The amount here is from a previous semester. This amount is calculated into the Balance due. ... If you choose to pay with a credit or...
  • Audit Overview - Solanco School District

    Audit Overview - Solanco School District

    Audit Overview. Audit in Accordance with: US Generally Accepted Auditing Standards. Government (Yellow Book) Auditing Standards. Uniform Guidance. Audit of period 7/1/15 - 6/30/16. Overview of Audit Process. Audit Findings: No significant deficiencies or material weaknesses are reported