Thanks Greg.
Multi-CPU is theoretical for now, tho conceivably I could use the idea
for balancing internal resources as part of an AI's personality.
My scratch plan if I had to scale to multi-head was to use node.js,
based on reputation a few years ago, so research would be needed.
With an average of 2 sessions a day, scaling is more about dreaming my
old life than a need. :-)
Bill
On 12/13/19 6:09 PM, Greg Wilkins wrote:
Bill,
Jetty has Proxy and Middleman components that can be used for load
balancing. Using jetty for balancing will never be as efficient as
dedicated balancers, however it can be a good idea if:
+ the decision of what back end to use is complex and needs to
inspect the request
+ if processing/transformation is to be done in the load balancer of
either request/response
+ the application is much more of a load than running the protocol,
so that any extra inefficiencies of app space balancing would be
outweighed by the gains from reducing load on the app servers themselves.
regards
On Sat, 14 Dec 2019 at 11:25, Bill Ross <[email protected]
<mailto:[email protected]>> wrote:
> But the question would be, how is the correct handler going to
be picked from that list?
Out of curiosity, would it be efficient/maintainable to use Jetty
as a load balancer, such that each handler would manage load for a
given back end, and they'd be chosen by sorting handlers (hanglers
once you can misspell) according to load?
Bill
On 12/13/19 3:07 PM, Greg Wilkins wrote:
Note also that if you have a need, there is nothing preventing
you from having a HandlerList within a ContextHandler.
But the question would be, how is the correct handler going to be
picked from that list?
For ContextHandlerCollection, the context path (and some
virtual host stuff) is used to pick which ContextHandler the
request is given to.
For a normal HandlerList, each listed handler is called in turn
until one of them handles it.
A ServletHandler picks a servlet by the pathInfo and will always
handle a request - if only with a 404, so a HandlerList of normal
ServletHandlers makes little sense.
But if you have some other criteria to select between different
ServletHandlers, then you can have a custom HandlerList within a
context that could apply that criteria.
On Fri, 13 Dec 2019 at 23:55, Karel Goderis <[email protected]
<mailto:[email protected]>> wrote:
Thanks Joakim
That’s clear.
The stages do in fact respond to the same URL endpoint; I
will have quick look if Filters (that filter based on some
PDU bytes) can be a solution for this kind of situation
Thanks
K
On 13 Dec 2019, at 12:03, Joakim Erdfelt <[email protected]
<mailto:[email protected]>> wrote:
Since you haven't details what your ServletHandler are
actually trying to do ("stage 1, stage 2, stage 3" means
nothing), this reply is generic.
A ServletContextHandler belongs to a single context Path.
It manages the ServletContext for all Servlets and Filters
and Listeners belonging to that ServletContext.
Each Servlet has a url-pattern it can belong to
Each Filter has a url-pattern it can participate in.
If you have multiple ServletHandlers, and expect them to
respond on the same url-pattern, then you have a problem.
You should only have 1 "endpoint" to a HTTP resource.
You *can* have that single "endpoint" respond differently
depending on request details (such as method, Content-Type,
existence of request body content, Accept headers, Cache
headers, etc...)
But that difference isn't handled by multiple servlets, it's
handled by a single servlet, with logic to produce different
responses accordingly.
If you have multiple ServletHandlers because some handlers
respond on different url-patterns, then great! You just use
different url-patterns when you add them to the
ServletContextHandler.
If you have multiple ServletHandlers because each handler
does some subset of actions, then you are abusing
ServletHandlers.
Use Filters for subsets and Servlets for "endpoint" logic.
Joakim Erdfelt / [email protected] <mailto:[email protected]>
On Fri, Dec 13, 2019 at 4:37 AM Karel Goderis
<[email protected] <mailto:[email protected]>> wrote:
Yes,
I am using a ServletConextHandler, however the question
is : can you do the equivalent of HandlerList but with
Servlets. AFAIK it is impossible to register different
Servlets using the same Context path
Tx
K
On 13 Dec 2019, at 11:33, Joakim Erdfelt
<[email protected] <mailto:[email protected]>> wrote:
Use a ServletContextHandler.
Don't use ServletHandlers, those are internal
structures not meant for direct usage.
Use ServletContextHandler.addServlet() and
ServletContextHandler.addFilter()
You can add the Servlet as a Class reference, or as a
Servlet instances (via a ServletHolder).
Joakim Erdfelt / [email protected]
<mailto:[email protected]>
On Fri, Dec 13, 2019 at 2:36 AM Karel Goderis
<[email protected] <mailto:[email protected]>> wrote:
Hi,
I have the practical need of splitting up a
protocol implementation in 3 “parts”, because the
protocol does a kind of “staged” setup whereby a
connection goes through these steps in order. I
also need the benefits of Contexts to maintain some
state. Ideally, I would like to have the equivalent
of a HandlerList but for Servlets being added to a
ServletContextHandler. How could this be achieved?
Wrt to this question, I am confused about the
ServletHolder.setServletHandler(). What is its
purpose? Does it replace the handle() methods of
the Servlet.class that is fed to the ServletHolder?
Obviously, I tried to use setServletHandler() with
a HandlerList, but that does not work. It is a bit
lacking in the documentation and examples of how to
used embedded Jetty.
My first attempt was something along the lines of
HandlerList setupHandlers = new HandlerList();
setupHandlers.addHandler(new StageOneHandler());
setupHandlers.addHandler(new StageTwoHandler());
setupHandlers.addHandler(new StageThreeHandler());
ServletHandler setupHandler = new
ServletHandler();
setupHandler.setHandler(setupHandlers);
ServletHolder setupHolder = new
ServletHolder(DefaultServlet.class);
pairSetupHolder.setServletHandler(setupHandler);
But I clearly missed something from an architecture
point of view
The (IMO) ugly workaround is to put the 3 stages in
a regular Servlet, and do an if-then based on some
bytes of the protocol payload, but I prefer the
more beautiful solution ;-) Any help is welcome
Thanks
Karel
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http://webtide.com
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