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From Jørgen Løland (JIRA) <j...@apache.org>
Subject [jira] Commented: (DERBY-2872) Add Replication functionality to Derby
Date Wed, 13 Feb 2008 15:15:10 GMT

    [ https://issues.apache.org/jira/browse/DERBY-2872?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12568577#action_12568577
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Jørgen Løland commented on DERBY-2872:
--------------------------------------

Code freeze for 10.4 is getting closer by the minute. It would be good to evaluate the funcspec
at this point and be explicit about which replication features will make it into this release
and which will be delayed for the next. As I see it, the following will have to be delayed
until 10.5:

* CLI for NetworkServerControl (this has already been mentioned in the funcspec)
* Depending on ETA of DERBY-2109, the system privilege for replication may or may not make
it into 10.4
* Copy the database from the master to the slave inside Derby by using the master-slave network
connection. Instead, a file system copy of the database to the slave location will be required
before replication can be started. This has the implication that startup of replication requires
these steps:

1) boot database 'x' on master
2) freeze 'x' (force log and data to disk and block write operations)
3) copy 'x' to slave location using file system copy
4) connect to 'x' with startSlave option on Derby serving slave
5) connect to 'x' with startMaster option on Derby serving master (includes unfreeze of 'x')

...as opposed to only doing the originally intended steps 4 and 5. FWIW, startup of replication
in MySQL requires a similar file system copy of the database.

Of course, both these issues can be addressed in 10.4 if someone volunteers to work on them.

I will update the funcspec with this information in a few days unless I hear objections.


> Add Replication functionality to Derby
> --------------------------------------
>
>                 Key: DERBY-2872
>                 URL: https://issues.apache.org/jira/browse/DERBY-2872
>             Project: Derby
>          Issue Type: New Feature
>          Components: Replication
>    Affects Versions: 10.4.0.0
>            Reporter: Jørgen Løland
>            Assignee: Jørgen Løland
>         Attachments: master_classes_1.pdf, poc_master_v2.diff, poc_master_v2.stat, poc_master_v2b.diff,
poc_slave_v2.diff, poc_slave_v2.stat, poc_slave_v2b.diff, poc_slave_v2c.diff, proof-of-concept_v2b-howto.txt,
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_funcspec_v5.html, replication_funcspec_v6.html, replication_funcspec_v7.html,
replication_funcspec_v8.html, replication_script.txt, slave_classes_1.pdf
>
>
> 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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