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From Rick Hillegas <Richard.Hille...@Sun.COM>
Subject Re: Opinions please - some questions regarding replication
Date Wed, 13 Feb 2008 15:02:13 GMT
Hi Jørgen,

Some unscientific ramblings of a layman follow...

Jørgen Løland wrote:
> I have a few questions regarding replication that would be great
> to hear the community's opinion on before the 10.4 branching. The
> reason for bringing this up before code freeze is that these will
> have impact on existing applications if changed later.
>
> 1. The master of a replicated database ships log records and
>    other information to the slave through a network socket. 8001
>    is currently default port for this communication. From
>    http://www.iana.org/assignments/port-numbers it seems that
>    this port is reserved for
>
>    vcom-tunnel    8001/tcp    VCOM Tunnel
>    vcom-tunnel    8001/udp    VCOM Tunnel
>
>    Should we change port, and maybe even register a port in IANA,
>    or is it fine as it is? I have no idea how long it will take
>    to register a port, but chances are it will be longer than the
>    time we have for 10.4 with the current plan. Another
>    alternative is to use a port from the range called "dynamic
>    and/or private ports" (49152 through 65535) BTW: I noticed
>    that 1527 is registered by Oracle, which may also be a
>    problem?
At first blush, registering a port seems like a good idea. It ought to 
reduce the likelihood of ugly surprises. I got the impression that the 
top range ( dynamic and/or private ports) was for short-lived, transient 
conversations. It's probably not the right range if you want to conduct 
a long-running conversation on your port.

A little mousing around turned up these resources: The process for 
registering a port is defined in section 19.9 of 
http://www.rfc-editor.org/rfc/rfc4340.txt and the corresponding form is 
at http://www.iana.org/cgi-bin/usr-port-number.pl It appears that IANA 
wants to give you a port number rather than vice-versa. So if you want 
to register a port, then our user documentation should say that the port 
used in 10.4 is likely to change in a future release.
>
>    tlisrv          1527/tcp    oracle
>    tlisrv          1527/udp    oracle
>
>    Note that this is only a question of default port. The port
>    number may be set explicitly by the client starting
>    replication.
Oops. Changing this would be a backward compatibility issue and I doubt 
you'll find much passion for this in the community.
>
> 2. About a week ago, Dibyendu Majumdar raised a question about
>    why the replication modules are placed under services and not
>    store. Should replication be moved from
>    org.apache.derby.{iapi|impl}.services.replication to e.g.
>    org.apache.derby.{iapi|impl}.store.replication, or is it OK to keep
>    the current placement?
>
> 3. Should replication be shipped in a separate JAR file? Pros and
>    cons as I see it:
>
>    + Remove 65KB (unjared) of class files from derby.jar
>    + Possible to have a different security policy file for replication?
>    - Yet another JAR file
>
This doesn't seem like excessive bloat to me.

Thanks,
-Rick


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