Ross Gardler escribió:
Tim Williams wrote:
On 8/14/06, Ross Gardler <[EMAIL PROTECTED]> wrote:
minimal requirement: an XMLConsumer/XMLProducer (easy and natural, sax
event handlers and a single method respectively) and some simple
lifecycle contract methods needed for being a part of the managed
environment.
I really should have been talking about the complexitites of writing a
generator. As we very rarely need to write transformers. Try writing a
generator that, for example, uses hibernate to communicate with a
relational database.
A hibernate generator does not make sense at all. You should ask people
using hibernate with cocoon. BTW, what have relational database in
common with forrest? Are we discussing about cocoon or forrest goals?
Please explain because it is not clear to me.
I think being in some sort of managed environment (e.g.
Spring) is likely needed in any real-world approach. So I'd turn this
around and ask where is the complexity?
First complexity: building Cocoon
Second complexity: building any component that has additional
dependencies
Third complexity: deploying a new (non-trivial) component within a plugin
Fourth complexity: a community that is pulling in many different
directions
There are many more but I will leave it at that. If you don't agree
then I suggest you actually try it before arguing the case. You can
then tell me where I am going wrong.
Of course, it can be argued that 1-3 are because Forrest was built
against a much older version of Cocoon and has failed to keep up (for
example why a plugins not Cocoon blocks?). I would respond that this
is because of the fourth complexity.
So, then it can be argued that we should be contributing to Cocoon and
helping resolve the fourth complexity. That may be the outcome of this
RT, it may not.
For the records, the cocoon community *recommended* all related projects
(including forrest) to stay with 2.1 *until* 2.2 get stabilized. This is
what lenya, hippo and daisy did and I did not see this kind of crisis
there. Hence is this our own fault? Should be the solution claiming that
cocoon is not for us or are there other reasons?
Decide what output plugin to use
--------------------------------
This is done by examining the requested URL. The actual selection of
the
output plugin is done within the Cocoon sitemap. I have all the same
arguments here as I do for input plugins, this only needs to be a
simple
lookup, not a complex pipeline operation.
I get the feeling you're basing this on the simplest use-case
imaginable. The output plugin is about the format of the output not
the content of the output. The sitemap benefits here allow for more
complex processing (e.g. user profiling, smart content delivery, etc.)
I disagree. The sitemap is a way of *configuring* this complex
processing, it is not the processing itself. The sitemap has become an
XML programming language and I hate it for that reason.
Have you ever dived in to the implementation and tried to do anything
useful in there?
Why is this so important? Is this forrest business?
The fact that the sitemap had become a programming language is one
reason why Cocoon came up with the flow engine (e.g. to get rid of
actions). But if you use the flow engine then you are programming with
Javascript, it's only a small step from there to Java. So are there
any benefits in using Javascript over Java?
You should know javascript is not java. It is not even a closer language
to java. Netscape used this name just because java was a buzzword at
that time. Hence, there is not just a small *jump* to java. BTW,
javascript is a programming language that is supposed to be used by HTML
developers right?
In my opinion the answer is a resounding no, at least for our use case.
Generate the output format
--------------------------
This is typically done by an XSLT transformation and/or by a third
party
library (i.e. FOP) I have the same arguments here as I do for the
generation of internal format documents, in fact the parts of Cocoon we
use are identical in both cases.
Yeah, output is just a transformer. Same thoughts as above.
OK, back to aggregation since I argued earlier that it belongs here.
Aggregation is nothing more than the collation of a number of
resources in response to a single request. It turns a single request
to a number of requests. Each individual request is handled just like
any other request. ASo what you have is a locationmap something like
this:
<map match="foo/bar/**">
<aggregate>
<location src="..." required="true"/>
<location src="..." required="false"/>
</aggegate>
<map>
Caching
-------
Cocoons Caching mechanism is pretty good, but it has its limitations
within Forrest. In particular, we have discovered that the Locationmap
cannot be cached efficiently using the Cocoon mechanisms.
This may be true. We had a novice working on LM caching at the time
and I've learned quite a bit since then. I'd like to re-evaluate this
before I'm willing to agree with with such a bold statement.
This illustrates my point exactly. I looked at this too and also
failed to get a better solution.
The reason I failed (and I guess the same for you) is that the code is
just so complex and jumbled that it's next to impossible to find ones
way around once one gets past the API.
Why you did not asked for help on the cocoon list. I am sure there are
some people willing to help. Just because we were unable to implement a
better cache mechanism, it does not mean something is complex.
This is now
one of the key bottlenecks in Forrest.
Based on? I'd like to see this profiling data. Knowing that the LM
is our way ahead I've been worried about squeezing every ounce where
we could but I was still under the impression that it isn't a
consequential performance bottleneck.
Try building the Cocoon docs. Its set up on a Forrestbot in our zone.
Even when co-located on the same physical machine as the source for
the content it takes over 30 minutes to build. It really is a horrible
solution.
If you want to profile it then you can get the forrest site from the
Cocoon-Whiteboard.
This is an extreme example case, but one that is quite common in my
experience using Forrest to do real document processing (as opposed to
web site generation).
We could work with Cocoon on their caching mechanism but there seems
little interest in this since our use case here is quite unusual. Of
course, we can do the work ourselves and add it to Cocoon. But why not
use a cacheting mechanism more suited to our needs?
So it's not 100% suitable so it's worthless? It fits in 98% percent
of our needs so I don't see this as a compelling argument.
That's unfair. I'm saying it is not perfect, therefore it is not
necessary to use it. I did not say it is not perfect so lets get rid
of it. Please take this in the context of all the other problems I am
highlighing rather than considering it as a single point.
Besides it doesn't work for the locationmap, so in fact it is not used
in some of the processing of every single request we make. That's
considerably more than "2%"
Ready Made Transformations
--------------------------
...
You seem to be
suggesting that Cocoon requires some big overhead to do transforms and
that's simply not the case.
That's right, I call 40Mb of bloat a fair big overhead for doing XSLT
transformations.
This time I really am oversimplifying, but I hope you see my point -
certainly that is how my customers see it. As a result I ended up, in
most cases, writing a series of Java components that I wired together
manually and plugged directly into whatever framework they were using.
This RT is about doing this in a more felxible and reusable way.
Yes, it is really over simplistic, because claiming that we use 40MB in
cocoon just for XSLT transformations is like telling we should close
forrest, because it is what forrest do too or perhaps we should
distribute a couple of XSLT files instead, right? I am taking into
account that XSLT transformations support is already built into java
1.5. BTW, the cocoon kernel is only 1.4 MB. :-)
This complexity makes it difficult for newcomers to get started in
using
Forrest for anything other than basic XSLT transformations.
...
My point is that newcomers are
going to find it difficult to deal with any framework that attempts to
achieve anything beyond the simplistic.
Yes, but if the framework is designed to do one job (publishing in our
case) then it is simpler to understand than if it is designed to do
every job (as with Cocoon).
There is no need to use every cocoon block.
The end result is that we have only one type of user - those doing XSLT
transformations.
Plugin Selection
----------------
This is done through the sitemap. This is perhaps where the biggest
advantage of Cocoon in our context can be found. The sitemap is a
really
flexible way of describing a processing path.
However, it also provides loads of stuff we simply don't need when all
we are doing is transforming from one document structure to another.
This
makes it complex to new users (although having our own sitemap
documentation would help here).
Finally, as discussed in the previous section, we don't need a complex
pipeline definition for our processing, we just need to plug an input
plugin to an output plugin via our internal format and that is it. We
have no need for all the sitemap bells and whistles.
I'm struggling to figure out what you think is forcing us into our
current apparently overly complex solution. Is it the sitemap grammar
that is complex?
Not the grammar itself (although I do hate the fact that we are now
programming using the sitemap). The complexity is in processing of
that gramar whic results in the selection of the processing path to take.
All we need to do is select the right plugins and make them work
together. Look at how many internal pipeline requests there are to do
this in Forrest now (its even worse if we use the dispatcher).
This is overly complex for what is ultimately a couple of lookups.
Learning curves aside, I'd rather sit on top of a framework that
supports a more complex solution than is my current problem because
experience has shown me that the initial requirements grow and I don't
want to have port when that growth happens.
This is exactly why I hate "catch all" frameworks. They try to be all
things to all people. I prefer to use what I need now and look at
expanding things when I find a use case that requires it. How can you
know in advance that the framework you choose is going to be adequate
for the job in hand? How do you know you won't eed Struts, or Ruby On
Rails, or Wicket or SpringMVC or whatever?
This is personal opinion and we should really leave it at the door.
Different people for different things. Our job is to decide what is
best for the project not for us as idividuals. I'll just leave you
with one though...
If I'm going hiking I do not struggle carrying a family tent on my
back just because I may have some more children at some point in the
future.
Sure, and this is why you should use only the cocoon blocks that are
needed for your work.
Conclusion
----------
Cocoon does not, IMHO, bring enough benefits to outweigh the
overhead of
using it.
That overhead is:
- bloat (all those jars we don't need)
this is going to be addressed with maven (argghhh) and/or osgi someday
- it's a recognized issue by many cocooners.
"someday" is the optimal word there. I've been waiting too long.
If we reject this RT based on this argument then I want to see Forrest
developers helping Cocoon sort this out rather than standing by
waiting for it to happen.
As I told initially, there was a bad decision to start using 2.2 too
early. And this is the cause of all this problems. I think it is not a
cocoon fault after all, as I told, the cocoon community gave and advise
that was reject by forrest. It is our own "mea culpa".
- complex code (think of your first attempt to write a transformer)
I've never written a transformer. I suspect that I could do it in a
day or less though depending upon the requirements. It's simply
implementing XMLConsumer by handling SAX events, not that
extraordinary for a SAX-stream-based framework. How do the many other
pipeline frameworks do transforms if not by handling SAX events?
Yes, transformers are simple. I should have picked non-trivial
generators as discussed above. Especially since this is a more common
requirement in the real world. That is we need input plugins to
inteface with existing corporate legacy code.
- complex configuration (sitemap, locationmap, xconf)
Like component managers nowadays, we've failed to strike a good
balance between flexibility (configurability) and ease of use.
I really can't agree with the "like component managers nowadays" part.
Have you actually worked with something like Spring? It is
unbelievably simple.
AFAIK, cocoon is migrating to spring.
- based on Avalon which is pretty much dead as a project
They are at least partially migrated to Spring for management
purposes. I understood that as a move to eventually migrate fully
from Avalon to Spring.
Don't be fooled by the "headlines". Look into the code. Until the
Avalon jars are gone then my point stands. Until someone here gets
into the Cocoon code and starts trying to disentangle things then my
point stands.
The avalon jars will be there for long time, the reason is because
cocoon should stay backward compatible with all the components created
in the lat years for our user base. Hence the avalon jar distribution is
not a measure of your claiming.
Why don't I do that? I have other things to do, I need Forrest to be
useful, I don't use, and have never used, Cocoon independantly of
Forrest (at least not commercially).
My case is rather the opposite. And I feel comfortable with cocoon. :-)
Best Regards,
Antonio Gallardo
