[infinispan-issues] [JBoss JIRA] (ISPN-5021) Nodes that finish the rebalance later can see outdated values

[Radim Vansa (JIRA)]

    [ https://issues.jboss.org/browse/ISPN-5021?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13319024#comment-13319024 ] 

Radim Vansa commented on ISPN-5021:
-----------------------------------

I intend to work on this issue, moving from two-phase to four-phase topology change (after ISPN-6938 and ISPN-7029 get integrated). I want to guarantee these properties when the topology is changing:
1. T(x+1).writeCH contains all nodes from Tx.readCH (this is the requirement to prevent the outdated values)
2. Tx.readCH and T(x+1).readCH has non-empty subset of nodes (that will allow no blocking for read commands && reading only entries node owns according to readCH)

Therefore, there will be these topologies:
* T0: readCH=old, writeCH=old
* T1: readCH=old, writeCH=old+new
* T2: readCH=old+new, writeCH=old+new
* T3: readCH=new, writeCH=old+new
* T4: readCH=new, writeCH=new

> Nodes that finish the rebalance later can see outdated values
> -------------------------------------------------------------
>
>                 Key: ISPN-5021
>                 URL: https://issues.jboss.org/browse/ISPN-5021
>             Project: Infinispan
>          Issue Type: Bug
>          Components: Core, State Transfer
>    Affects Versions: 7.0.2.Final
>            Reporter: Dan Berindei
>            Assignee: Pedro Ruivo
>            Priority: Critical
>              Labels: testsuite_stability
>
> Copied from [ISPN-4444|https://issues.jboss.org/browse/ISPN-4444?focusedCommentId=13022645#comment-13022645]
> If the CH_UPDATE command is delayed on the old owner, the new owners might update the key without the old owner knowing, and a locality check on the old owner won't help.
> I remember one thing that struck me when reading the Raft algorithm was that they install configuration changes symmetrically, in 3 phases. We might need to do the same for our rebalance:
> 1. T0: read_ch=old, write_ch=old
> 2. start a rebalance
> 3. T1: read_ch=old, write_ch=old+new
> 4. new owners have all the data
> 5. T2: read_ch=new, write_ch=old+new
> 6. remove old cache entries and ignore further writes
> 7. T3: read_ch=new, write_ch=new



--
This message was sent by Atlassian JIRA
(v7.2.3#72005)