On Thu, Mar 30, 2017 at 4:09 PM, Martin Grigorov <[email protected]>
wrote:
>
>
> Whenever a stateful pages is used (touched) the SessionEntry is updated,
> i.e. the page is put into it.
>
Yes I can see that happening in PageStoreManager.storeTouchedPages()
> The SessionEntry is stored as an attribute in the HTTP Session.
>
I'm not seeing this. In the wicket.Session class there is line :
private transient ISessionStore sessionStore;
Which is loaded from the Application each request. The SessionStore
contains the SessionEntry's no???
> The web container has logic to detect if the HTTP session has been updated
> in a request and if it was then it replicates the whole session to the
> other nodes.
>
Yes I'm seeing the http session replicated no issues.
> Once the session is replicated it is deserialized. Here
> SessionEntry#readObject() comes to play. It reads the pages from the
> SessionEntry and stores them into the disk (via IDiskStore).
> So the stateful pages should be available in the disks of all nodes.
> Stateless pages are always recreated from scratch, so they are not
> replicated.
>
If this is the case why is wicket saying this page is stateless as the
SessionEntry is never replicated across?:
public class HomePage extends WebPage {
private static final long serialVersionUID = 1L;
public HomePage() {
super();
Session s= Session.get();
s.bind();
Integer i = (Integer)s.getAttribute("foo");
if (i == null) {
i = new Integer(0);
}
i++;
s.setAttribute("foo",i);
add(new Label("version", (Integer)s.getAttribute("foo")));
add(new Link<Void>("link1") {
@Override
public void onClick()
{
setResponsePage(new NextPage());
}
});
add(new Link<Void>("link2") {
@Override
public void onClick()
{
setResponsePage(new HomePage());
}
});
add(new AbstractDefaultAjaxBehavior() {
@Override
protected void respond(AjaxRequestTarget target) {
getSession().setAttribute("someKey", UUID.randomUUID().toString());
System.out.println("SLEEEPING");
try {
Thread.sleep(3000);
}catch(Exception e) {
}
System.out.println("DONE");
}
@Override
public void renderHead(Component component, IHeaderResponse response) {
super.renderHead(component, response);
String js = "(" + getCallbackFunction().toString() +")();";
response.render(OnDomReadyHeaderItem.forScript(js));
}
});
// TODO Add your page's components here
}
}
Sorry for all these questions but I must get to the bottom of this (5 days
work so far). Many thanks
>
>
> >
> >
> > thanks
> >
> > On Tue, Mar 28, 2017 at 9:39 PM, Martin Grigorov <[email protected]>
> > wrote:
> >
> > > Hi,
> > >
> > > Did you mention already which version of Wicket you use ?
> > > There was an improvement related to reusing the page parameters when
> > > constructing a new page instance in 7.0.0.
> > > I have the feeling you are using 6.x. Am I correct ?
> > >
> > > Martin Grigorov
> > > Wicket Training and Consulting
> > > https://twitter.com/mtgrigorov
> > >
> > > On Tue, Mar 28, 2017 at 7:22 PM, Wayne W <[email protected]>
> > > wrote:
> > >
> > > > Hello Martin,
> > > >
> > > > so I've been trying to still get to the bottom of this days later. So
> > my
> > > > understanding is getting better and it appears that the session
> itself
> > is
> > > > replicated fine. However I've tracked my issue down to the following:
> > > >
> > > > - If I have a page that has 2 links at the top. Link A is a
> > Bookmarkable
> > > > link back to the same page - it is also mounted thus: mountPage(
> > > > "/cube/documents/${0}", CubeDocumentPage.class); It has a Long page
> > param
> > > > needed to construct the page ( i.e. /cube/documents/12345 ). The
> second
> > > > link B is just a simple new Link<Void>("B") .
> > > > - If both instances are up and running , lets say I am on instance
> A. I
> > > > visit link A 3 times. I then kill instance A and I am balanced over
> to
> > > > instance B. If I visit link B , the PageStoreManager cannot find the
> > > page
> > > > that contains link B in the store and then tries to create a new
> > instance
> > > > of the page - the problem is then for some reason the page parameters
> > are
> > > > always null and the Long is never passed. Why is the page parameter
> > > always
> > > > null here? Trying to debug it, is seems the IPageManager is got from
> > the
> > > > wicket Application instance and not the Session, and this
> IPageManager
> > > > looks for a RequestAdaptor. Somewhere the page parameters are lost?.
> > > >
> > > > However I can get it to work this way:
> > > > - start instance A, visit the page and say click link A 3 times.
> > > > - Now start up instance B
> > > > - Kill instance A
> > > > - Click on the link B and this time the PageStoreManager finds the
> page
> > > and
> > > > there the link B and everything works fine.
> > > > It only works if I don't visit another page just after instance B
> > starts
> > > > up.
> > > >
> > > >
> > > > I will do some more debugging tomorrow to try and understand this
> > > > PageStoreManager/request adaptor bit more. But if you have any ideas
> > I'd
> > > > appreciate it.
> > > > Thanks
> > > >
> > > >
> > > >
> > > > On Fri, Mar 24, 2017 at 12:48 PM, Martin Grigorov <
> > [email protected]>
> > > > wrote:
> > > >
> > > > > Hi,
> > > > >
> > > > > On Fri, Mar 24, 2017 at 1:31 PM, Wayne W <
> > [email protected]>
> > > > > wrote:
> > > > >
> > > > > > Thanks Martin,
> > > > > >
> > > > > > I have a theory what this is, perhaps you could confirm?
> > > > > >
> > > > > > What I observe is the following with the replication: If I visit
> > > page A
> > > > > and
> > > > > > then visit page B, then kill the instance I am on the session is
> > > > > > successfully failed over to the other node. Now I'm still looking
> > at
> > > > > page B
> > > > > > in the browser - if I hit back on the browser I get
> > > > PageExpiredException.
> > > > > > Is this the expected behaviour?
> > > > > >
> > > > >
> > > > > No.
> > > > > The expected behavior is to see the latest state of page A.
> > > > >
> > > > >
> > > > > >
> > > > > > If it IS the expected behaviour, then the reason I think that I
> > have
> > > an
> > > > > > issue with the page with the AbstractDefaultAjaxBehavior is
> because
> > > the
> > > > > > code in the AbstractDefaultAjaxBehaviour.respond is adding
> > > components
> > > > to
> > > > > > the page which in turn marks the Session dirty which in turn
> > > replicates
> > > > > the
> > > > > > session. If only the last page/session commit is only replicated
> it
> > > > could
> > > > > > explain why I get a ComponentNotFound exception from the page as
> > > > > > it overwriten by the update from the AbstractDefaultAjaxBehavior
> > > > > >
> > > > >
> > > > > Any time the page is marked as dirty Wicket will store it in 1) the
> > > HTTP
> > > > > session and 2) on the disk
> > > > > 1) will notify the web server (e.g. Tomcat) that it has to
> replicate
> > > the
> > > > > session because some attribute has been modified
> > > > > At node2 Wicket will detect the replicated session in #readObject()
> > and
> > > > > store it on the disk.
> > > > > From now on node2 will have the same history for that page as
> node1,
> > > i.e.
> > > > > PageA and PageB.
> > > > >
> > > > > In addition:
> > > > > Updates made in an Ajax requests do not add a new entry in the
> > history
> > > > > (storages) but overrides the previous entry for that page instance!
> > > > > I.e. when PageA is rendered Wicket will assign a pageId for it,
> e.g.
> > 5,
> > > > and
> > > > > store it in the disk.
> > > > > Later when you make a change to PageA:5 in Ajax request then Wicket
> > > will
> > > > > override the entry on the disk.
> > > > > If you make a change in non-Ajax request then Wicket will assign a
> > new
> > > > > pageId, e.g. 6, and add a new entry in the history (disk), so you
> > will
> > > > have
> > > > > two entries for this session.
> > > > > Later when you open PageB then this will be pageId 7, etc.
> > > > >
> > > > >
> > > > > >
> > > > > > What do you think?
> > > > > >
> > > > > >
> > > > > >
> > > > > > On Fri, Mar 24, 2017 at 9:31 AM, Martin Grigorov <
> > > [email protected]
> > > > >
> > > > > > wrote:
> > > > > >
> > > > > > > Hi,
> > > > > > >
> > > > > > > Once the http session is replicated this method should be
> > executed
> > > on
> > > > > the
> > > > > > > node that did not process the request
> > > > > > > org.apache.wicket.page.PageStoreManager.SessionEntry#
> > readObject().
> > > > > > > Here Wicket will either store the page(s) on the disk or will
> > > > schedule
> > > > > > them
> > > > > > > for storing.
> > > > > > > There is no much usage of Loggers here so you will have to
> > attach a
> > > > > > > debugger and see what happens.
> > > > > > >
> > > > > > > Martin Grigorov
> > > > > > > Wicket Training and Consulting
> > > > > > > https://twitter.com/mtgrigorov
> > > > > > >
> > > > > > > On Thu, Mar 23, 2017 at 6:11 PM, Wayne W <
> > > > [email protected]>
> > > > > > > wrote:
> > > > > > >
> > > > > > > > If I put the AbstractDefaultAjaxBehavior back in, it always
> > > fails.
> > > > > If I
> > > > > > > > remove the AbstractDefaultAjaxBehavior most of the time it
> > works,
> > > > but
> > > > > > > every
> > > > > > > > now and then it fails to replicate. Its really inconsistent.
> > > > > > > >
> > > > > > > > I have no idea how to get to the bottom of this. Any pointers
> > or
> > > > help
> > > > > > is
> > > > > > > > much appreciated.
> > > > > > > >
> > > > > > > > On Thu, Mar 23, 2017 at 4:53 PM, Wayne W <
> > > > > [email protected]>
> > > > > > > > wrote:
> > > > > > > >
> > > > > > > > > So it seems the homepage is not the only page. However
> > removing
> > > > the
> > > > > > > > > AbstractDefaultAjaxBehavior makes no difference I still get
> > the
> > > > > same
> > > > > > > > > issues. Just don;t know where to start with this one. Is
> > there
> > > a
> > > > > way
> > > > > > I
> > > > > > > > can
> > > > > > > > > turn on the logging around replication in wicket?
> > > > > > > > >
> > > > > > > > > On Thu, Mar 23, 2017 at 4:27 PM, Wayne W <
> > > > > > [email protected]>
> > > > > > > > > wrote:
> > > > > > > > >
> > > > > > > > >> Hi Martin,
> > > > > > > > >>
> > > > > > > > >> no - I still get the ComponentNotFoundException in the new
> > > > > instance.
> > > > > > > :-/
> > > > > > > > >>
> > > > > > > > >> On Thu, Mar 23, 2017 at 3:57 PM, Martin Grigorov <
> > > > > > > [email protected]>
> > > > > > > > >> wrote:
> > > > > > > > >>
> > > > > > > > >>> Hi,
> > > > > > > > >>>
> > > > > > > > >>> On Thu, Mar 23, 2017 at 4:20 PM, Wayne W <
> > > > > > > [email protected]>
> > > > > > > > >>> wrote:
> > > > > > > > >>>
> > > > > > > > >>> > Hi Martin,
> > > > > > > > >>> >
> > > > > > > > >>> > that was a typo on my part. I've been doing a lot more
> > > > testing
> > > > > > > > before I
> > > > > > > > >>> > replied to make sure things are as I say. This is what
> I
> > am
> > > > > > > > observing:
> > > > > > > > >>> >
> > > > > > > > >>> >
> > > > > > > > >>> > - I have a 2 node tomcat cluster setup with apache
> > > > balancing
> > > > > > > > between
> > > > > > > > >>> > them locally on my machine.
> > > > > > > > >>> > - Testing with a very simple Wicket app I can see
> the
> > > > > > > replication
> > > > > > > > is
> > > > > > > > >>> > working fine when shutting down either instance.
> > > > > > > > >>> > - Testing with our very heavy weight wicket app it
> > > > sometimes
> > > > > > > work
> > > > > > > > >>> and
> > > > > > > > >>> > sometimes does not.
> > > > > > > > >>> >
> > > > > > > > >>> > Now the last point above I have narrowed down to our
> > > > homepage.
> > > > > > If I
> > > > > > > > am
> > > > > > > > >>> not
> > > > > > > > >>> > on the homepage the replication seems to work ok.
> However
> > > if
> > > > I
> > > > > am
> > > > > > > on
> > > > > > > > >>> the
> > > > > > > > >>> > homepage I always get a ComponentNotFoundException when
> > > > failing
> > > > > > > over
> > > > > > > > >>> to the
> > > > > > > > >>> > other instance.
> > > > > > > > >>> > The homepage has an AbstractDefaultAjaxBehavior which
> is
> > > > called
> > > > > > > once
> > > > > > > > >>> the
> > > > > > > > >>> > page is rendered, this in turn adds to the the page a
> > > > DataView
> > > > > > > > >>> containing a
> > > > > > > > >>> > lot of content and links. The user needs to be logged
> in
> > > > before
> > > > > > > they
> > > > > > > > >>> see
> > > > > > > > >>> > the homepage, so the session is already setup.
> > > > > > > > >>> >
> > > > > > > > >>> > I don't know what it is about this page that breaks the
> > > > > > > replication.
> > > > > > > > Is
> > > > > > > > >>> > there anything around the ajax part that could do this?
> > Any
> > > > > > > pointers
> > > > > > > > >>> would
> > > > > > > > >>> > be most welcome as it will be a long long task to break
> > > that
> > > > > page
> > > > > > > > down
> > > > > > > > >>> and
> > > > > > > > >>> > do rounds and rounds of cluster testing
> > > > > > > > >>> >
> > > > > > > > >>>
> > > > > > > > >>> Let's try something!
> > > > > > > > >>> In you Ajax callback method do something like:
> > > > > > > > >>> getSession().setAttribute("someKey",
> > > > > UUID.randomUUID().toString())
> > > > > > > > >>> Does this trigger replication ?
> > > > > > > > >>>
> > > > > > > > >>>
> > > > > > > > >>> >
> > > > > > > > >>> > many thanks
> > > > > > > > >>> >
> > > > > > > > >>> >
> > > > > > > > >>> >
> > > > > > > > >>> >
> > > > > > > > >>> > On Wed, Mar 22, 2017 at 12:34 PM, Martin Grigorov <
> > > > > > > > >>> [email protected]>
> > > > > > > > >>> > wrote:
> > > > > > > > >>> >
> > > > > > > > >>> > > Hi,
> > > > > > > > >>> > >
> > > > > > > > >>> > > "I can stop one of the instances and I'm not logged
> in"
> > > > > > > > >>> > > This statement says that you don't really have a
> > properly
> > > > > > > > configured
> > > > > > > > >>> > > failover.
> > > > > > > > >>> > > If those two Tomcat instances are in a cluster then
> the
> > > > http
> > > > > > > > sessions
> > > > > > > > >>> > > should be replicated and you should stay logged in no
> > > > matter
> > > > > > > which
> > > > > > > > >>> one is
> > > > > > > > >>> > > serving the request.
> > > > > > > > >>> > > Wicket will store the used stateful page at the disks
> > for
> > > > all
> > > > > > > > >>> Tomcats in
> > > > > > > > >>> > > the cluster, if it the replication is actually
> working!
> > > > > > > > >>> > >
> > > > > > > > >>> > >
> > > > > > > > >>> > > On Wed, Mar 22, 2017 at 1:02 PM, Wayne W <
> > > > > > > > >>> [email protected]>
> > > > > > > > >>> > > wrote:
> > > > > > > > >>> > >
> > > > > > > > >>> > > > Hi,
> > > > > > > > >>> > > >
> > > > > > > > >>> > > > We have 2 instances of Tomcat running with Apache
> > > sitting
> > > > > in
> > > > > > > > front
> > > > > > > > >>> > > > balancing between the Tomcat instances. I have
> > session
> > > > > > > > replication
> > > > > > > > >>> > setup
> > > > > > > > >>> > > > which seems to work for basic bookmarkable links on
> > the
> > > > > > pages.
> > > > > > > I
> > > > > > > > >>> can
> > > > > > > > >>> > stop
> > > > > > > > >>> > > > one of the instances and I'm not logged in as it
> > > failover
> > > > > to
> > > > > > > the
> > > > > > > > >>> other
> > > > > > > > >>> > > > instance.
> > > > > > > > >>> > > >
> > > > > > > > >>> > > > However for normal Link<?> and ajax links etc I get
> > > > > > > > >>> > > > ComponentNotFoundException thrown as the new
> > instance
> > > > > cannot
> > > > > > > > find
> > > > > > > > >>> it
> > > > > > > > >>> > in
> > > > > > > > >>> > > > the session it seems.
> > > > > > > > >>> > > >
> > > > > > > > >>> > > > Clearly I'm not understanding how wicket manages
> the
> > > page
> > > > > > state
> > > > > > > > or
> > > > > > > > >>> I've
> > > > > > > > >>> > > > configured something wrong.
> > > > > > > > >>> > > >
> > > > > > > > >>> > > > Does wicket support full session failover ?
> > > > > > > > >>> > > >
> > > > > > > > >>> > > > Many thanks
> > > > > > > > >>> > > >
> > > > > > > > >>> > >
> > > > > > > > >>> >
> > > > > > > > >>>
> > > > > > > > >>
> > > > > > > > >>
> > > > > > > > >
> > > > > > > >
> > > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
>
