I have written a graphing engine (very similar to what BigCharts.com
offers). Basically, it's an ASPX page that accepts parameters and calls
back-end business objects (dlls) to create a graph. When the graph is
created as a jpeg, it is returned to the browser as binary data. When it is
used at a low volume, it performs great and returns correctly drawn graphs
in a timely manner. However when the amount of traffic is increased to a
high volume, the graphs come back distorted. I've done some research on this
issue and have found that when .NET creates an object in memory, it is not
thread safe. For instance, if an ASPX page gets called several times at
once and each call creates an object called oGraph, it will create several
oGraph objects. However, when an instance of the ASPX page goes to reference
the properties or methods of oGraph, it doesn't care about which instance in
memory that it uses. It will use one that it didn't create. What I end up
with is mutated graphs. For example, if two calls were made simultaneously
to create a 90 day IBM graph and a one day intraday MSFT graph, I will end
up with a graph with IBM as the title and a plot that reflects MSFT intraday
data. Many times it just looks like pieces of one graph drawn on top of the
other. Does anyone know of a way to tell the ASPX page (and the objects it
calls) to 'mind it's own business', so to say, and only use the specific
instances of objects it initiates? I have tried using
System.Threadin g.Monitor.Enter \Exit on all of my objects and have also tried
the SyncLock blocks, as well. Any help with this would be greatly
appreciated.
5  1572 
you don't say which graphic library you are using. is it thread safe? (many
aren't). did you use vb module fields? these are not thread safe. by default
asp.net is thread safe, and object instances are local to the the running
thread.
-- bruce (sqlwork.com)
"Ron Mexico" <mi***********@ mworld.com> wrote in message
news:uW******** ******@TK2MSFTN GP09.phx.gbl... I have written a graphing engine (very similar to what BigCharts.com
offers). Basically, it's an ASPX page that accepts parameters and calls
back-end business objects (dlls) to create a graph. When the graph is
created as a jpeg, it is returned to the browser as binary data. When it
is used at a low volume, it performs great and returns correctly drawn
graphs in a timely manner. However when the amount of traffic is increased
to a high volume, the graphs come back distorted. I've done some research
on this issue and have found that when .NET creates an object in memory, it
is not thread safe. For instance, if an ASPX page gets called several
times at once and each call creates an object called oGraph, it will create
several oGraph objects. However, when an instance of the ASPX page goes to
reference the properties or methods of oGraph, it doesn't care about which
instance in memory that it uses. It will use one that it didn't create.
What I end up with is mutated graphs. For example, if two calls were made
simultaneous ly to create a 90 day IBM graph and a one day intraday MSFT
graph, I will end up with a graph with IBM as the title and a plot that
reflects MSFT intraday data. Many times it just looks like pieces of one
graph drawn on top of the other. Does anyone know of a way to tell the
ASPX page (and the objects it calls) to 'mind it's own business', so to
say, and only use the specific instances of objects it initiates? I have
tried using System.Threadin g.Monitor.Enter \Exit on all of my objects and
have also tried the SyncLock blocks, as well. Any help with this would be
greatly appreciated.
Thank you for the quick reply, Mr. Barker. I am using the graphics library
that comes with .NET (GDI+, I guess) System.Drawing. Graphics and
System.Drawing. Bitmap are the objects. If ASP.NET is thread safe by
default, how else would I be getting combined images? Here's a more
descriptive explanation of how the application works: There are basically
three 'layers' to my application.
1. The ASPX page. All it does is take the parameters from the querys
string and create a new instance of the SecurityGraph object (an object I
wrote) and set some properties (Ticker symbol, plot color, graph
height/width, frequency, etc). The SecurityGraph object has a Generate
method. The last thing the ASPX page does is call that method.
2. SecurityGraph. When the Generate method is called in the SecurityGraph
object, the database is queried based on the information set in the
properties of the SecurityGraph object set by the ASPX page which are loaded
into the new instance of the MWGraph object.
3. MWGraph. This object is where the graph actually gets drawn using the
Graphics and Bitmap objects.
So if ASP.NET is thread safe, I'm guessing the only thing that can be
happening to cause the output of several graphs to have shared properties is
because GDI+ isn't thread safe and the Graphics and Bitmap object are being
shared when several graphs are being created at once by the same
aspx-invoked chain of SecurityGraph and MWGraph objects?
As for 'vb module fields', I'm not quite sure what you are referring to.
Please explain further. Thanks again.
"Bruce Barker" <br************ ******@safeco.c om> wrote in message
news:eM******** *****@TK2MSFTNG P10.phx.gbl... you don't say which graphic library you are using. is it thread safe?
(many aren't). did you use vb module fields? these are not thread safe. by
default asp.net is thread safe, and object instances are local to the the
running thread.
-- bruce (sqlwork.com)
"Ron Mexico" <mi***********@ mworld.com> wrote in message
news:uW******** ******@TK2MSFTN GP09.phx.gbl...I have written a graphing engine (very similar to what BigCharts.com
offers). Basically, it's an ASPX page that accepts parameters and calls
back-end business objects (dlls) to create a graph. When the graph is
created as a jpeg, it is returned to the browser as binary data. When it
is used at a low volume, it performs great and returns correctly drawn
graphs in a timely manner. However when the amount of traffic is increased
to a high volume, the graphs come back distorted. I've done some research
on this issue and have found that when .NET creates an object in memory,
it is not thread safe. For instance, if an ASPX page gets called several
times at once and each call creates an object called oGraph, it will
create several oGraph objects. However, when an instance of the ASPX page
goes to reference the properties or methods of oGraph, it doesn't care
about which instance in memory that it uses. It will use one that it
didn't create. What I end up with is mutated graphs. For example, if two
calls were made simultaneously to create a 90 day IBM graph and a one day
intraday MSFT graph, I will end up with a graph with IBM as the title and
a plot that reflects MSFT intraday data. Many times it just looks like
pieces of one graph drawn on top of the other. Does anyone know of a way
to tell the ASPX page (and the objects it calls) to 'mind it's own
business', so to say, and only use the specific instances of objects it
initiates? I have tried using System.Threadin g.Monitor.Enter \Exit on all
of my objects and have also tried the SyncLock blocks, as well. Any help
with this would be greatly appreciated.
the .net graphics library is thread safe (but not completely multithreaded -
just a performance issue). your code must not be thread safe.
you either have static (shared in vb) variables, or you used a vb module
variable (a member variable defined in a vb module), instead of instance
data, which has led to your problem.
-- bruce (sqlwork.com)
"Ron Mexico" <mi***********@ mworld.com> wrote in message
news:u4******** ********@TK2MSF TNGP15.phx.gbl. .. Thank you for the quick reply, Mr. Barker. I am using the graphics
library that comes with .NET (GDI+, I guess) System.Drawing. Graphics and
System.Drawing. Bitmap are the objects. If ASP.NET is thread safe by
default, how else would I be getting combined images? Here's a more
descriptive explanation of how the application works: There are basically
three 'layers' to my application.
1. The ASPX page. All it does is take the parameters from the querys
string and create a new instance of the SecurityGraph object (an object I
wrote) and set some properties (Ticker symbol, plot color, graph
height/width, frequency, etc). The SecurityGraph object has a Generate
method. The last thing the ASPX page does is call that method.
2. SecurityGraph. When the Generate method is called in the SecurityGraph
object, the database is queried based on the information set in the
properties of the SecurityGraph object set by the ASPX page which are
loaded into the new instance of the MWGraph object.
3. MWGraph. This object is where the graph actually gets drawn using the
Graphics and Bitmap objects.
So if ASP.NET is thread safe, I'm guessing the only thing that can be
happening to cause the output of several graphs to have shared properties
is because GDI+ isn't thread safe and the Graphics and Bitmap object are
being shared when several graphs are being created at once by the same
aspx-invoked chain of SecurityGraph and MWGraph objects?
As for 'vb module fields', I'm not quite sure what you are referring to.
Please explain further. Thanks again.
"Bruce Barker" <br************ ******@safeco.c om> wrote in message
news:eM******** *****@TK2MSFTNG P10.phx.gbl... you don't say which graphic library you are using. is it thread safe?
(many aren't). did you use vb module fields? these are not thread safe.
by default asp.net is thread safe, and object instances are local to the
the running thread.
-- bruce (sqlwork.com)
"Ron Mexico" <mi***********@ mworld.com> wrote in message
news:uW******** ******@TK2MSFTN GP09.phx.gbl...I have written a graphing engine (very similar to what BigCharts.com
offers). Basically, it's an ASPX page that accepts parameters and calls
back-end business objects (dlls) to create a graph. When the graph is
created as a jpeg, it is returned to the browser as binary data. When it
is used at a low volume, it performs great and returns correctly drawn
graphs in a timely manner. However when the amount of traffic is
increased to a high volume, the graphs come back distorted. I've done
some research on this issue and have found that when .NET creates an
object in memory, it is not thread safe. For instance, if an ASPX page
gets called several times at once and each call creates an object called
oGraph, it will create several oGraph objects. However, when an instance
of the ASPX page goes to reference the properties or methods of oGraph,
it doesn't care about which instance in memory that it uses. It will use
one that it didn't create. What I end up with is mutated graphs. For
example, if two calls were made simultaneously to create a 90 day IBM
graph and a one day intraday MSFT graph, I will end up with a graph with
IBM as the title and a plot that reflects MSFT intraday data. Many times
it just looks like pieces of one graph drawn on top of the other. Does
anyone know of a way to tell the ASPX page (and the objects it calls) to
'mind it's own business', so to say, and only use the specific instances
of objects it initiates? I have tried using
System.Threa ding.Monitor.En ter\Exit on all of my objects and have also
tried the SyncLock blocks, as well. Any help with this would be greatly
appreciate d.
On Tue, 1 Nov 2005 14:41:30 -0500, "Ron Mexico"
<mi***********@ mworld.com> wrote: For instance, if an ASPX page gets called several times at
once and each call creates an object called oGraph, it will create several
oGraph objects.
Yes, assuming oGraph is not defined with the Shared keyword in VB.
However, when an instance of the ASPX page goes to reference
the properties or methods of oGraph, it doesn't care about which instance in
memory that it uses.
If oGraph is defined as a field in your Page derived class, then a
page instance will always reference the same oGraph object.
It will use one that it didn't create.
You'd only see this problem if oGraph is Shared among multiple
instances, or perhaps you have shared / static fields inside of
oGraph. Perhaps you could share your code?
--
Scott http://www.OdeToCode.com/blogs/scott/
Looks like you are using a variable that is shared accross sessions. Do you
use a member tagged with the "static" (in c#) or "shared" (in VB.NET)
keywords ?
Those variable are shared accross the whole application and in the case of
ASP.NET it means accross users (as in ASP.NET it's a single application used
by multiple users).
--
Patrice
"Ron Mexico" <mi***********@ mworld.com> a écrit dans le message de
news:uW******** ******@TK2MSFTN GP09.phx.gbl... I have written a graphing engine (very similar to what BigCharts.com
offers). Basically, it's an ASPX page that accepts parameters and calls
back-end business objects (dlls) to create a graph. When the graph is
created as a jpeg, it is returned to the browser as binary data. When it
is used at a low volume, it performs great and returns correctly drawn graphs
in a timely manner. However when the amount of traffic is increased to a
high volume, the graphs come back distorted. I've done some research on
this issue and have found that when .NET creates an object in memory, it is not
thread safe. For instance, if an ASPX page gets called several times at
once and each call creates an object called oGraph, it will create several
oGraph objects. However, when an instance of the ASPX page goes to
reference the properties or methods of oGraph, it doesn't care about which instance
in memory that it uses. It will use one that it didn't create. What I end up
with is mutated graphs. For example, if two calls were made simultaneously
to create a 90 day IBM graph and a one day intraday MSFT graph, I will end
up with a graph with IBM as the title and a plot that reflects MSFT
intraday data. Many times it just looks like pieces of one graph drawn on top of
the other. Does anyone know of a way to tell the ASPX page (and the objects
it calls) to 'mind it's own business', so to say, and only use the specific
instances of objects it initiates? I have tried using
System.Threadin g.Monitor.Enter \Exit on all of my objects and have also
tried the SyncLock blocks, as well. Any help with this would be greatly
appreciated.
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