[jira] Commented: (DERBY-2872) Add Replication functionality to Derby

["Ole Solberg (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/DERBY-2872?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12524652 ] 

Ole Solberg commented on DERBY-2872:
------------------------------------

I have a few comments to the

Functional Specification for Derby Replication - rev. 4.0 - table in "Interacting with the replication feature":


1) As I understand it 'Start Master' is only allowed on the host which will serve as master, 
and 'Start Slave' is only allowed on the host to serve as slave, 
thus the I think the "operation field" in the table should state this (as for 'Failover' and 'Stop Replication').

2) I think the "pre-conditions" field should say something like 
* 'Start Master': 
  ** A database with the name <dbname> must exist on the (master) host where 
     this command is issued. 
     (was: 'Restricted to the same machine that the database resides.')
* 'Start Slave':
  ** The (slave) host, where this command is issued,
     must not already be serving a database named <dbname> as slave. 
     (was: 'Restricted to the same machine that the database resides.')
* 'Failover':
  ** The (slave) host, where this command is issued,
     must be serving a database named <dbname> as slave.
     (was: 'Restricted to the same machine that the database resides.')
* 'Stop Replication':
  ** The (master) host, where this command is issued,
     must be serving a database named <dbname> as master.
     (was: 'Can be issued only on the master and the master in turn ...
      ... the slave is shut down as well')


The current text in 'Stop Replication'/"pre-conditions" is, I think, rather part of 
the functional specification of the command and should be put elsewhere? e.g. 
in a subchapter giving more details on 'Stop Replication'?



> Add Replication functionality to Derby
> --------------------------------------
>
>                 Key: DERBY-2872
>                 URL: https://issues.apache.org/jira/browse/DERBY-2872
>             Project: Derby
>          Issue Type: New Feature
>          Components: Miscellaneous
>    Affects Versions: 10.4.0.0
>            Reporter: Jørgen Løland
>            Assignee: Jørgen Løland
>         Attachments: proof_of_concept_master.diff, proof_of_concept_master.stat, proof_of_concept_slave.diff, proof_of_concept_slave.stat, replication_funcspec.html, replication_funcspec_v2.html, replication_funcspec_v3.html, replication_funcspec_v4.html, replication_script.txt
>
>
> It would be nice to have replication functionality to Derby; many potential Derby users seem to want this. The attached functional specification lists some initial thoughts for how this feature may work.
> Dag Wanvik had a look at this functionality some months ago. He wrote a proof of concept patch that enables replication by copying (using file system copy) and redoing the existing Derby transaction log to the slave (unfortunately, I can not find the mail thread now).
> DERBY-2852 contains a patch that enables replication by sending dedicated logical log records to the slave through a network connection and redoing these.
> Replication has been requested and discussed previously in multiple threads, including these:
> http://mail-archives.apache.org/mod_mbox/db-derby-user/200504.mbox/%3c426E04C1.1070904@yahoo.de%3e
> http://www.nabble.com/Does-Derby-support-Transaction-Logging---t2626667.html

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