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Date: Fri, 21 May 2010 09:09:15 -0700 (PDT)
From: "\(David\) Ming Xia" <david.ming.xia@ibol.biz>
Reply-To: david.ming.xia@ibol.biz
Subject: Roller's implementation on conditional Get
To: Mailing List Apache Roller User <user@roller.apache.org>,
  Mailing List Apache Roller Developer <dev@roller.apache.org>
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Hi, Everyone.

=C2=A0=C2=A0 This is about the implementation of conditional Get in Roller =
4.0.1.

=C2=A0=C2=A0 As far as I see, Roller 4.0.1 supports conditional Get. Upon r=
equest, Roller checks the =E2=80=98If-Modified-Since=E2=80=99 field in the =
http header, and compares it with =E2=80=98Last-Modified=E2=80=99 attribute=
 on server side.=C2=A0 And then either responds with a fresh page with stat=
us code 200, or responds with a status code 304.=C2=A0=C2=A0=C2=A0=C2=A0=20

=C2=A0 What I feel concerned is the part retrieving =E2=80=98Last-Modified=
=E2=80=99.=C2=A0 It is implemented in org.apache.roller.weblogger.ui.render=
ing.servlets.PageServlet.=C2=A0 Attached you can see the sequence diagram, =
which depicts the related class.=C2=A0 Every time a weblog entry is added o=
r changed, the=C2=A0 =E2=80=98last-modified=E2=80=99 field of corresponding=
 website table will be updated.=C2=A0 For any http request, PageServlet has=
 to go through a JPA named query to get the =E2=80=98last-modified=E2=80=99=
 value.=C2=A0 That value is not cached in memory, and it is not kind of way=
 that the entities float across context (any how...).=C2=A0 So as far as I =
can see, it is hard query.=C2=A0=20

=C2=A0=C2=A0 But for one page query, there are usually at least ten http qu=
ery, including query for text/html file, css file, js file, images, and so =
on.=C2=A0 So for 10000 simultaneous page requests, there will be at least 1=
00000 simultaneous database queries.=C2=A0=C2=A0Furthermore, for any seriou=
s production environment, database and application server are on different =
tiers and the connection is encrypted with SSL.=C2=A0 So the picture to me =
it that, for limited concurrent users it is fine, but=C2=A0when request vol=
ume goes up, the server may suddenly chocked up.
=C2=A0
=C2=A0=C2=A0 I would appreciate if some=C2=A0one could respond and explain =
this, or=C2=A0provide some good advices=C2=A0
=C2=A0
=C2=A0
Thank you very much.
=C2=A0
=C2=A0
David

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<table cellspacing=3D"0" cellpadding=3D"0" border=3D"0" ><tr><td valign=3D"=
top" style=3D"font: inherit;"><DIV>Hi, Everyone.</DIV>
<DIV><BR>&nbsp;&nbsp; This is about the implementation of conditional Get i=
n Roller 4.0.1.<BR></DIV>
<DIV>&nbsp;&nbsp; As far as I see, Roller 4.0.1 supports conditional Get. U=
pon request, Roller checks the =E2=80=98If-Modified-Since=E2=80=99 field in=
 the http header, and compares it with =E2=80=98Last-Modified=E2=80=99 attr=
ibute on server side.&nbsp; And then either responds with a fresh page with=
 status code 200, or responds with a status code 304.&nbsp;&nbsp;&nbsp;&nbs=
p; </DIV>
<DIV><BR>&nbsp; What I feel concerned is the part retrieving =E2=80=98Last-=
Modified=E2=80=99.&nbsp; It is implemented in org.apache.roller.weblogger.u=
i.rendering.servlets.PageServlet.&nbsp; Attached you can see the sequence d=
iagram, which depicts the related class.&nbsp; Every time a weblog entry is=
 added or changed, the&nbsp; =E2=80=98last-modified=E2=80=99 field of corre=
sponding website table will be updated.&nbsp; For any http request, PageSer=
vlet has to go through a JPA named query to get the =E2=80=98last-modified=
=E2=80=99 value.&nbsp; That value is not cached in memory, and it is not ki=
nd of way that the entities float across context (any how...).&nbsp; So as =
far as I can see, it is hard query.&nbsp; <BR></DIV>
<DIV>&nbsp;&nbsp; But for one page query, there are usually at least ten ht=
tp query, including query for text/html file, css file, js file, images, an=
d so on.&nbsp; So for 10000 simultaneous page requests, there will be at le=
ast 100000 simultaneous database queries.&nbsp;&nbsp;Furthermore, for any s=
erious production environment, database and application server are on diffe=
rent tiers and the connection is encrypted with SSL.&nbsp; So the picture t=
o me it that, for limited concurrent users it is fine, but&nbsp;when reques=
t volume goes up, the server may suddenly chocked up.</DIV>
<DIV>&nbsp;</DIV>
<DIV>&nbsp;&nbsp; I would appreciate if some&nbsp;one could respond and exp=
lain this, or&nbsp;provide some good advices&nbsp;</DIV>
<DIV>&nbsp;</DIV>
<DIV>&nbsp;</DIV>
<DIV>Thank you very much.</DIV>
<DIV>&nbsp;</DIV>
<DIV>&nbsp;</DIV>
<DIV>David<BR></DIV></td></tr></table>
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