Hey Filip,
what I see is you want make an innovative step. Great, I m very
motivated to
help that we implement a next generation.
But, why do we this implementation not inside a sandbox, branch or
separate module?
Last year I learned that big changes are great, but it is easy to
make failures at very little
details, like the compress flag bug. To design a new implementation
is risky. A lot of
projects and people now use very succesfull the current tomcat 5.5.15
cluster. Some people are
waiting that we release the cross context replication to support
portal development. Please, I do not want to stop the innovation, but
why do we not start the new cluster design at a separate module and
set the current code base at maintaince mode?
Peter Roßbach
Am 23.02.2006 um 12:59 schrieb Filip Hanik - Dev Lists:
Peter Rossbach wrote:
>I have add the compress flag inside the protocol.
>It is usefull to send message with an without compression.
>For short messages it is not usefull to compress, it is an overhead.
There is no question whether compression is useful or not.
The compression flag should have never been added in the protocol
in the first place,
Compression can and should be done on a higher level, and the
algorithm should be pluggable.
Adding it to the protocol is like adding a compression flag to a
TCP frame, and its a hack,
And it caused 4 stable releases of tomcat to be broken.
The flag should have been a flag in the payload,
configurable by the component requesting to send the data as that
component is suitable for making that decision
compression will still be configurable on a per message basis, but
with a different design.
>Before 5.5.15 you made a vote that we carefull with protocol changes,
I didn't make a vote, I advised against it, as if you don't
understand the code as it is pretty detailed and complex, then you
shouldn't be changing it without a full set of regression tests. 4
broken releases should testify to that.
>Why you now change so much inside one minor tomcat release ?
Cause it is long needed and long awaited. The way the code got
cluttered in 5.5 with JMX,core replication, io and session
replication all mixed together, means that I cant extend nor can I
implement any useful features. For example, if I wanted to
implement a ComplexTcpCluster class, I have to rewrite all JMX code
again, I have to rewrite all statistics code again, I have to
basically rewrite session replication again. This was never the
intention of this module. The module should provide for much
flexibility.
>Why do you think we must move the cluster JMX MBean code?
For the exact reasons above. I could have written the entire module
in one single class, JMX, IO, session logic, member logic. But
there was a reason I didn't. Flexibility. Hardcoding JMX against
code is not flexible. Instead the right way is to build the MBeans
against an interface, cause I can change the underlying component
without having to rewrite the JMX code. The way it is now is
doesn't allow for this.
>The most tomcat components have no separate MBean classes
and this is a good thing? probably not, but and the rest of the
components do, does not set a precedence. Otherwise, if we had one
bad class, then all others should follow?
>When we move to separate classes we get
>a lot of classes with redundant get/setter attributes and
operation signatures.
not at all, if you move it to a separate MBean class, I can have 50
different cluster implementations
The way it is now, I would have 50 different MBeans, now that is
redundancy. The way I am suggesting, you will have one at all times.
>The reasons
>behind I added the JMX code direclty into the cluser component
implementation are:
JMX has been added to several component, not just the cluster
class. for reasons mentioned above, this is not suitable.
>-1 for this change.
I would be careful putting -1 out there, it causes a lot of
friction, especially when they have no justification.
I am working on a improved design, a design that was intended from
the beginning but I got sidetracked with another job not giving me
the time to complete the full circle. I now have that opportunity
and intend to see it through. If you want to be a part of it, I
suggest you come with constructive ideas to move the project
forward and not just veto changes with no justifications. If we
didn't want this project to improve we would still be using Tomcat
3, but the world of hi-tech changes everyday. All of those changes
have the intention for improvements, not all of them succeed. But
that is nature of the industry we are in.
I hope this answers all your concerns and makes you redraw your
veto or justify it with a better suggestion.
best regards,
Filip
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