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  1. JGroups
  2. JGRP-2112

Sticky site masters

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Details

    • Feature Request
    • Status: Resolved (View Workflow)
    • Major
    • Resolution: Done
    • None
    • 3.6.12, 4.0
    • None

    Description

      If members in one site send messages to site masters of other sites, if we have multiple site masters, then reordering can occur.

      Example:

      • Member C in site LON sends messages C1 and C2 to site NYC
      • C1 picks SM1 and C2 picks SM2
      • Although site masters process messages in delivery order, because C1 and C2 travel through different site masters, C2 could pass C1, leading to ordering issues

      Design

      • When sending a message to the one of the site masters of the current site, or from a site master to a remote site master, we invoke a callback to pick the site master based on the original caller
      • Note that this only applies when we have more than one site master.
      • The callback passes the address of the original caller and the list of available site masters, and needs to return a site master
      Transactions
      • Transactions by different originators with overlapping key sets cannot be reliably ordered
      • Transactional support therefore requires single site masters
      • This should not be an issue as transactions bundle multiple updates, so the number of messages sent is less than non-transactional updates

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              rhn-engineering-bban Bela Ban
              rhn-engineering-bban Bela Ban
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