[PAX-WEB] "Transactional" approach to register web items in HS/WS

[Grzegorz Grzybek]

Hello

I'm wondering about one scenario...

Background

We have:

 - org.osgi.service.http.HttpService, aka HS, which may be used to register servlets only (including "resources")

 - org.ops4j.pax.web.service.WebContainer, aka WC, which may be used to register other web items - filters, listeners, welcome files, error pages, login configurations, security constraints, etc - most (if not all) items that can be declared in WEB-INF/web.xml

The problem

While this worked for a long time and is fundamental to pax-web, I see some flaws here:

 - pax-web-extender-war, when parsing/processing WEB-INF/web.xml, acts in kind of "transactional" way - it uses visitor pattern "surounded" by calls to WebContainer#begin() and WebContainer#end() - this is not everything, the important check is org.ops4j.pax.web.service.internal.HttpServiceStarted#isWebAppWebContainerContext() which is a hacky way to check if we're actually inside "transaction" - it prevents starting the context after each servlet/filter/... from web.xml

 - non pax-web-extender-war usage is a series of registrations - and if we register, say, 10 servlets in a row, the underlying web context is restarted 10 time (see e.g., org.ops4j.pax.web.service.undertow.internal.Context#addServlet())

The proposal

I'd like to make this behavior less implicit - so we can manually "demarcate transactioins" related to web item registration - avoiding, if possible, changes to org.ops4j.pax.web.service.WebContainer interface.

What do you think?

best regards

Grzegorz Grzybek

[Achim Nierbeck]

Hi Grzegorz,

AFAICR the transactional part was needed to make sure we don't restart the web-application with every change while executing the web.xml configuration.

If you find better ways. Go for it :)

regards, Achim

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[Grzegorz Grzybek]

Hi

2018-06-19 6:31 GMT+02:00 'Achim Nierbeck' via OPS4J <op...@googlegroups.com>:

Hi Grzegorz,

AFAICR the transactional part was needed to make sure we don't restart the web-application with every change while executing the web.xml configuration.

If you find better ways. Go for it :)

Yes - it works with web.xml only (pax-web-extender-war and its visitors). Without changing API of WebContainer we can't do much - but (referring to my 2nd email), I can create a ManagedServiceFactory that monitors etc/org.ops4j.pax.web.context-<name>.cfg factory PIDs and uses the configs to alter http contexts of choice - and because it'll be (that's my plan) part of pax-web-runtime bundle, I can use protected and non exposed methods of serviceController to "demarcate" transactions.

The WebContainer.end() method is perfect to ... end the transaction, but WebContainer.begin() is called only by pax-web-extender-war visitors and it'll be tricky to make it more generic - but maybe I can think of something.

regards

Grzegorz Grzybek

[françois papon]

Hi,

I'm very interested by this and I like the idea of the ManagedServiceFactory !

Let me know if I can help :)

regards,

François

[Grzegorz Grzybek]

Hello

I just got back from my holidays. Actually the ManagedServiceFactory idea is implemented and described here: https://ops4j1.jira.com/wiki/spaces/paxweb/pages/354025473/HTTP+Context+processing

If you think there's place for improvements (and there surely is!), please suggest/implement.

Thanks!

best regards

Grzegorz Grzybek

[françois papon]

Great !

I take a look ;)

Thanks !

François