5:41 a.m.
Hello
Based on Allan Zhang's comments I have closed my pull requests and opened
this one https://github.com/weld/core/pull/1990 which is a better match
for the recommendations in the sessionmanagement spec. I still have not
heard back from my customer so I will compile an updated test fix and
chase them up. If they approve, or if they do not reply soon I will create
pull requests for the other branches.
Regards
Benjamin
From: Allan Zhang/Toronto/IBM
To: Matej Novotny <manovotn(a)redhat.com>
Cc: Benjamin Confino <BENJAMIC(a)uk.ibm.com>, Shinji Ohtsuka
<EB92769(a)jp.ibm.com>, Emily Jiang <EMIJIANG(a)uk.ibm.com>,
weld-dev(a)lists.jboss.org
Date: 06/05/2020 17:42
Subject: Re: [EXTERNAL] Re: [weld-dev] Propagation of
org.jboss.weld.context.ConversationContext.conversations through session
failover
> Unless stated otherwise
above:
> IBM United Kingdom Limited - Registered in England and Wales with number
Unless stated otherwise above:
IBM United Kingdom Limited - Registered in England and Wales with number
741598.
Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU
Shouldn't Liberty consider (at least after restart) any access to
a
collection-based session property as an action marking that property
"dirty"?
Liberty already has write option of ALL_SESSION_ATTRIBUTES to mark the
property "dirty" but customer wont use it for performance reasons.
The PR fix is following the JEE spec where property "dirty" require
setAttribute() call.
https://docs.oracle.com/cd/E13924_01/coh.340/e13819/sessionmanagement.htm
As a general rule, all session attributes should be treated as immutable
objects if possible. This ensures that developers are consciously aware
when they change attributes. With mutable objects, modifying attributes
often requires two steps: modifying the state of the attribute object, and
then manually updating the session with the modified attribute object by
calling javax.servlet.http.HttpSession.setAttribute(). This means that
your application should always call setAttribute() if the attribute value
has been changed, otherwise, the modified attribute value will not
replicate to the backup server.
Thanks
Allan Zhang
From: Matej Novotny <manovotn(a)redhat.com>
To: Benjamin Confino <BENJAMIC(a)uk.ibm.com>
Cc: Shinji Ohtsuka <EB92769(a)jp.ibm.com>, Emily Jiang
<EMIJIANG(a)uk.ibm.com>, weld-dev(a)lists.jboss.org, Allan Zhang
<zhang(a)ca.ibm.com>
Date: 2020-05-06 07:52 AM
Subject: [EXTERNAL] Re: [weld-dev] Propagation of
org.jboss.weld.context.ConversationContext.conversations through session
failover
Hi,
thanks for explanation, I understand the flow now.
However, your suggested PR still looks like a workaround more than a fix
to me.
I doubt Weld is the only case where this will emerge. You can easily store
any collection in session and expect it to behave like we do.
So in the very least, anything of type java.util.Collection that is stored
in session is susceptible to this behaviour.
Shouldn't Liberty consider (at least after restart) any access to a
collection-based session property as an action marking that property
"dirty"?
Regards
Matej
----- Original Message -----
From: "Benjamin Confino" <BENJAMIC(a)uk.ibm.com>
To: "Matej Novotny" <manovotn(a)redhat.com>
Cc: "Shinji Ohtsuka" <EB92769(a)jp.ibm.com>, "Emily Jiang"
<EMIJIANG(a)uk.ibm.com>, weld-dev(a)lists.jboss.org, "Allan
Zhang" <zhang(a)ca.ibm.com>
Sent: Tuesday, May 5, 2020 3:59:30 PM
Subject: RE: [weld-dev] Propagation of
org.jboss.weld.context.ConversationContext.conversations through session
failover
Hello Matej
No worries about the delay, my customer has not responded so you are
ahead
of schedule. You are correct, the purpose of this PR is to trigger
the
"dirty" state in liberty's session storage. Let me try and describe the
flow again and hopefully it will be clearer:
A1) The application is started for the first time. A conversation map is
created and stored into the session context. This marks it as dirty.
A2) The application puts stuff into the map. Lets say this leaves the
map
in State A
A3) The server is told to shut down.
A4) Liberty sees the map is dirty and saves map State A to persistent
storage.
B1) The server starts again.
B2) Weld retrieves the conversation map (State A) from persistent
storage.
Since it already has a map it does not put anything into session
storage.
Thus the map is clean.
B3) The application does more stuff, moving the map to (State B).
B3) The server is told to shut down.
B4) Liberty sees the map is clean, it doesn't transfer anything to
persistent storage.
C1) The server starts again.
C2) Weld retrieves the conversation map (State A). This is the wrong
state.
My PR changes B2 so that Weld will set the same map back into session
storage. Then in B4 liberty will see the map is dirty and save State B
to
storage, ensuring the correct state is retrieved at C2.
We do have alternative solutions, for example you can configure Liberty
to
store everything regardless of whether it is dirty or not. However
this
has performance implications and so my customer does not want to use
that
option.
Regards
Benjamin
From: Matej Novotny <manovotn(a)redhat.com>
To: Benjamin Confino <BENJAMIC(a)uk.ibm.com>
Cc: weld-dev(a)lists.jboss.org, Allan Zhang <zhang(a)ca.ibm.com>, Shinji
Ohtsuka <EB92769(a)jp.ibm.com>, Emily Jiang <EMIJIANG(a)uk.ibm.com>
Date: 05/05/2020 12:17
Subject: [EXTERNAL] Re: [weld-dev] Propagation of
org.jboss.weld.context.ConversationContext.conversations through session
failover
I finally found some time to look into this, it took longer than I
anticipated, sorry for that.
Firstly, I am not quite following the flow of the reproducer you
described.
Weld creates the conversation map and stores in into the session on
creation. We then retrieve this map from session whenever needed and
store
additional things into it.
All the while we use the same map (the same reference, or object if you
will)....so Liberty should see the same state in it, right? Or am I
missing something obvious?
I am not familiar with how Liberty deals with server shutdown and how it
stores session attributes, but i would expect that if you just grab the
existing map from there, it will be up to date.
The PRs you sent seem superfluous to me - you are overriding the
attribute
with exactly the same thing. probably just to trigger
"dirty" state in
your session storage?
Regards
Matej
----- Original Message -----
> From: "Benjamin Confino" <BENJAMIC(a)uk.ibm.com>
> To: "Matej Novotny" <manovotn(a)redhat.com>
> Cc: weld-dev(a)lists.jboss.org, "Allan Zhang" <zhang(a)ca.ibm.com>,
"Shinji
Ohtsuka" <EB92769(a)jp.ibm.com>, "Emily Jiang"
> <EMIJIANG(a)uk.ibm.com>
> Sent: Wednesday, April 29, 2020 11:56:43 AM
> Subject: RE: [weld-dev] Propagation of
org.jboss.weld.context.ConversationContext.conversations through session
> failover
> Thank you for the heads up. When it's time to think
about delivery
I'll
be
> sure to create a PR against 3.1 and I presume you'd like me to leave
> master alone for now?
> Regards
> Benjamin
>
From: Matej Novotny <manovotn(a)redhat.com>
> To: Benjamin Confino <BENJAMIC(a)uk.ibm.com>
> Cc: weld-dev(a)lists.jboss.org, Allan Zhang <zhang(a)ca.ibm.com>,
Shinji
> Ohtsuka <EB92769(a)jp.ibm.com>, Emily Jiang
<EMIJIANG(a)uk.ibm.com>
> Date: 29/04/2020 09:51
> Subject: [EXTERNAL] Re: [weld-dev] Propagation of
> org.jboss.weld.context.ConversationContext.conversations through
session
> failover
>
Hi,
> I'll take a look later today.
> Note that master branch is no longer Weld 3.x, it is 4.x (Jakarta EE
9)
> and the CI there is going bonkers yet as I am in the middle of
changing
> it.
> If you want to file a PR against Weld 3, you can use 3.1 branch for
that.
> Regards
> Matej
> ----- Original Message -----
> > From: "Benjamin Confino" <BENJAMIC(a)uk.ibm.com>
> > To: weld-dev(a)lists.jboss.org
> > Cc: "Allan Zhang" <zhang(a)ca.ibm.com>, "Shinji
Ohtsuka"
> <EB92769(a)jp.ibm.com>, "Emily Jiang" <EMIJIANG(a)uk.ibm.com>
> > Sent: Tuesday, April 28, 2020 2:31:44 PM
> > Subject: [weld-dev] Propagation of
> org.jboss.weld.context.ConversationContext.conversations through
session
> failover
> > > Hello weld
> > > I had a customer report that they were getting
conversation not
found
> > exceptions when restarting their server and visiting a url
with a
?cid=1
> > suffix.
> > > After investigation I believe the issue is that
weld was acquiring
it's
> > ConversationContext.conversations from the session database via
> > com.ibm.ws.session.store.db.DatabaseSession.getMultiRowAppData().
Once
> weld
> > had retrieved the conversations map it would then decide that since
the
> map
> > was already in the session attributes there was no need to put it
back
> into
> > the attributes.
> > > This means that Liberty did not realise the
conversations map had
been
> > updated, and did not store it's updated state into the
database when
the
> > server shut down again.
> > > I have submitted a pair of pull requests that asks
weld to mark the
> > conversation map as dirty upon access - this behaviour is gated
behind
> > ConfigurationKey.RESET_HTTP_SESSION_ATTR_ON_BEAN_ACCESS - I
have
tested
> it
> > locally and it works. The next step is to prepare a test fix for the
> > customer to verify. However I wanted to send you this quick note to
keep
> you
> > in the loop.
> > > Regards
> > Benjamin
> > Unless stated otherwise above:
> > IBM United Kingdom Limited - Registered in England and Wales with
number
> > 741598.
> > Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire
PO6
> 3AU
> > > _______________________________________________
> > weld-dev mailing list
> > weld-dev(a)lists.jboss.org
>
https://urldefense.proofpoint.com/v2/url?u=https-3A__lists.jboss.org_mail...
> 741598.
> Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6
3AU
Unless stated otherwise above:
IBM United Kingdom Limited - Registered in England and Wales with number
741598.
Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6
3AU