Filip Hanik - Dev Lists wrote:
I wanted to start a wish list of what we can move forward with, here is
a short list of items that I had in mind as a starter
Here's my opinion on these. I think most of them are not a good idea,
actually.
1. Session replication - stateless backup location
Store the backup location of a session as part of the sessionId,
similar to the jvmRoute but opposite.
This way, you can scale a cluster horizontally, since the location of
the backup node doesn't have to be known until you fail over.
No idea about that.
2. Add a block/no-block parameter to InputFilter.doRead and
OutputFilter.doWrite
InputFilter -> public int doRead(ByteChunk chunk, Request unused,
boolean block) throws IOException;
OutputFilter -> public int doWrite(ByteChunk chunk, Response unused,
boolean block) throws IOException;
Servlet 3.0 will most likely expose non blocking read/write through
the servlet API, this will get us there ahead of time
Haven't thought of how we expose this API yet though, but more will
follow
I think it's too early to speculate on what the Servlet API may add, and
I don't see any benefit this would bring at this point. I am managing to
implement non blocking functionality without major problems without
these additional calls. I also think your API proposal for Comet in
trunk is inappropriate, and I will come back with my original proposal,
which I like more and more. So -1 for this one.
3. Consolidate connector code
Currently we have
Http11Processor/Http11NioProcessor/Http11AprProcessor doing almost the
same thing, there is much that
can be consolidated to make the code more maintainable
Essentially, you create a Endpoint base line interface.
At the same time we could consolidate the Internal(In/Out)put buffers
as they are copies too.
We have some fairly tuned endpoints now, it would also be nice to make
these protocol agnostic.
This has been tried before (I was supporting it), but the endpoints (and
connectors) have a fairly different processing logic. The result was
actually more complex than the original version, so I removed it. -1 too.
4. Startup -> server.xml warnings
If one enters an invalid element or attribute that is simply ignored
today, at least output an info or warn message letting the
admin know if its misconfiguration.
That's going to be hard to do in a consistent way.
5. Finish bayeux -> I started this in sandbox, took me a while to
understand the protocol, and its not as cool as I thought it would be
but I still feel its important for it to be part of Tomcat
Ok. You could try to come up with something better if you think it's not
good enough.
6. Auto context logging
Automatically create loggers for each context, so that one doesn't
have to specify one per context in logging.properties
Of course, you can turn on/off the auto context logger through
logging.properties
I don't like that:
- very little logging occurs through the context logger (or maybe it's a
default for the whole webapp like if you added a file handler in
logging.properties ?)
- JULI already provides a separate logging environment for the webapp
(because it uses a separate classloader), and webapps interested in that
can easily configure it using a logging.properties
- JULI specific (if this is actually done, I would like to remove log4j
support)
- and most importantly, would automagically be creating zillions of
small logfiles, so I like the idea of people configuring it in better
than configuring it out
7. File cache - use MappedByteBuffers for the file cache, that way the
send file operation can benefit even more
when you have two direct buffers, and you also avoid reading the disk
each time for a file
ideas on this came from Jeanfrancois Arcand.
(http://fisheye5.cenqua.com/browse/glassfish/appserv-http-engine/src/java/com/sun/enterprise/web/connector/grizzly/FileCache.java?r=1.21)
I dislike gimmick cache functionality inside the connector (worst
Grizzly idea ever ...), where actually the overhead of the default
servlet is very slim. In the real world people could instead:
- write a caching valve using sendfile which would fit their needs
better and which will have a couple more % of overhead
- use a separate webserver for static resources if they have so many of them
- would have a lodbalancer/proxy nullifying the benefit
8. Add getName()/setName() to the WebappClassLoader, name of the web app
classloader will correspond to the one of the Context container
Applications like Terracotta or AOP apps can much easier plug in and
be able to share data when they know what loader the class came from
Really ? How would they know that this corresponds to something
meaningful ? It's possible to determine the webapp name in a similar
proprietary way without this, but making the change seems harmless.
9. Add the configuration option to start the connectors after all apps
are deployed
If some applications are taking long to startup, load balancers are
already trying to send requests to the Tomcat instance, which is just
bound to a port, but not yet taking requests
Very easy to do (I added a system property). This has some drawbacks
though, and I considered it JBoss specific.
10.Turn our embedded thread pools into Tomcat Executor thread pools,
same performance but pluggable. Instead of having them hidden in the end
point code
The executor based pools have really bad performance, so I don't see any
reason to stop using the simpler pools. This does not remove any
pluggability (a configured executor will be used). I added executors as
an experiment, and was really let down by the performance. Knowing the
results, I would not have bothered adding the feature ...
11.Timestamps & System.currentTimeMillis
System.currentTimeMillis is invoked everywhere during the chain of
events for a HTTP requests, even though most dates only need precision
down to the second.
I've received feedback that this could be improved by keeping a time
service, that updates a timestamp every second, and therefor reduces the
number of system calls
I think we would need to prove the theory before committing to the
implementation, but that should be pretty easy
I don't see that many calls being made, and many need the millisecond
precision (= not a HTTP date). I would like evidence that
System.currentTimeMillis is some sort of performance bottleneck before
supporting these changes.
12.Comet sample webapp
While most folks want to start with Comet, it is a strange question,
tons of users on the user list just are having a hard time getting kick
started
This isn't really something which should be proposed, it's part of the docs.
I was thinking we can keep this list on Wiki or in a text file in SVN,
http://wiki.apache.org/tomcat/6xFeatures
My own view is to do a number of changes, but keep the 6.0.x branch as
most changes I support could fit in there (for example, my own Comet API
changes - arguably the most significant change - are pretty much
backwards compatible, and as a result could occur there).
Rémy
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