[jboss-jira] [JBoss JIRA] (JGRP-2112) Sticky site masters

[Sebastian Łaskawiec (JIRA)]

    [ https://issues.jboss.org/browse/JGRP-2112?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13536440#comment-13536440 ] 

Sebastian Łaskawiec commented on JGRP-2112:
-------------------------------------------

This probably can't happen if the sites use Load Balancers as frontends. This way you will never send a message from C (LON) to C1 and C2 (NYC).

> Sticky site masters
> -------------------
>
>                 Key: JGRP-2112
>                 URL: https://issues.jboss.org/browse/JGRP-2112
>             Project: JGroups
>          Issue Type: Feature Request
>            Reporter: Bela Ban
>            Assignee: Bela Ban
>             Fix For: 3.6.12, 4.0
>
>
> 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
> h4. 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
> h5. 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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