Re: remoting channel woes - C# Discussion Boards

17-Oct-03 11:37

I've written a very small remoting app, a server that exposes one method from a dll, and a client that connects and calls that method. Most of the time this works fine. But if the client crashes, and I restart it, any subsequent connections to the server cause an exception. If I restart the server everything is fine. It seems to me that if the clients' connection to the server channel is disconnected improperly, the server is hosed. Is there any way to periodically check to see if a channel is 'stuck'? Otherwise I'll have to set up some kind of schedule of periodically unmarshalling/disconnecting and then re-marshalling/connecting, just in case the server is stuck. That just seems inelegant to me.

Thanks for any suggestions,
jt

Heath Stewart18-Oct-03 10:42

18-Oct-03 10:42

What calling convention are you using for the remoting type? (i.e., client-activated / server-activated, single-call / singeton, etc.)

-----BEGIN GEEK CODE BLOCK-----
Version: 3.21
GCS/G/MU d- s: a- C++++ UL@ P++(+++) L+(--) E--- W+++ N++ o+ K? w++++ O- M(+) V? PS-- PE Y++ PGP++ t++@ 5 X+++ R+@ tv+ b(-)>b++ DI++++ D+ G e++>+++ h---* r+++ y+++
-----END GEEK CODE BLOCK-----

qek20-Oct-03 5:04

20-Oct-03 5:04

It's a single call, no server config file, it's all in the code

Heath Stewart20-Oct-03 6:00

20-Oct-03 6:00

The only thing that I can think of is that the server is in the middle of doing something with the client and either throws an unhandled exception (that can't get passed to the client because it doesn't exist, so instead the remoting host must catch it) or tries to handle an exception and does something even more nasty.

Since it is a singleton and Remoting is supposed to be (:P) smart enough to handle disconnect situations, the remoting object itself must be doing something to screw up it's host (i.e., IIS, Windows Service, et. al.).

Since you said you're setting up the remoting object via code, check to make sure that any unhandled exceptions don't cause your entry point to continue and exit, causing your app to quit - or worse, cause the CLR to unload (like any calls to Environment.Exit(int)).

qek20-Oct-03 11:02

20-Oct-03 11:02

I think it's fixed. I wasn't checking the validity of the server name in the client app (which was throwing an exception and generally causing problems), and since then I haven't been able to duplicate the problem, but I'm still curious as to if it's possible to check the 'status'-so to speak- of a remoting session

Heath Stewart20-Oct-03 11:38

20-Oct-03 11:38

Shortly after I posted my possible problem, I got to thinking: have you ever checked after this "crash" if the service was still responding? If the host for the remoting object was hosed, it shouldn't respond. This indicates an error with the host, such as the remoting object throwing an exception that could be unhandled in the host and would effectively kill the host. If so, you shouldn't get a service response.

I'm glad it's fixed, but should ever anything like this happen again, check to see if the service itself is responding (i.e., ping the service using a non-activation client like soapsuds.exe or wsdl.exe (depending on the host)). That would most definitely be interesting to know and might help you figure out who to blame (i.e., the remote object vs. remoting infrastructure vs. the host).

qek27-Oct-03 10:14

27-Oct-03 10:14

OK, it happened again when I changed some of the code, here is the relevant exception info

Error: System.Runtime.Remoting.RemotingException: Server encountered an internal error. For more information, turn on customErrors in the server's .config file
.

Server stack trace:

Exception rethrown at [0]: at System.Runtime.Remoting.Proxies.RealProxy.HandleReturnMessage(IMessage req Msg, IMessage retMsg)
at System.Runtime.Remoting.Proxies.RealProxy.PrivateInvoke(MessageData& msgData, Int32 type)

It seems to me the server is throwing back the exception (HandleReturnMessage). Again a restart of the server fixes the problem (no changes in the code just restarting clears it up). The problem is the server still responds locally (i.e. other parts of it still work), just the remoting is hosed.

Heath Stewart27-Oct-03 10:23

27-Oct-03 10:23

Did you try using soapsuds.exe or something to see if the object still responds at all? (Or are you already sure that it doesn't.)

qek27-Oct-03 10:50

27-Oct-03 10:50

I'm sure. It's hosed.

Heath Stewart27-Oct-03 10:53

27-Oct-03 10:53

I'm not sure what to think, then. Either you've uncovered a major bug in the Remoting infrastructure or (no offense meant) you've put one there. The only thing I can think of is something I've stated before. The Remoting object is throwing an exception that the host isn't gracefully handling and the host, as a result, dies.

When you say "other parts of the app" - is this all in a single executable, this "app" you mention? I could be wrong if the app still lives, but still maybe not. If the exception causes the message pump to quit or die, the app will terminate. We had this happen with a Windows Service-hosted remoting object I wrote sometime back (since fixed by existing...er, better exception handling).

qek27-Oct-03 11:46

custom attribute question

27-Oct-03 11:46

Let me elaborate:
I have three projects, server, client, dll

The server is a single windows app that just exports the methods in the dll through remoting. It also creates a local instance of the dll.

The dll is just two methods that both call Shell(), with different parameters.

the client is a console app that connects to the server to access the remoted methods, and calls one or the other.

When the client can't connect without an exception being thrown, the server is still running, and the local instance still functions. I have exception handling in the dll (which is where the error says it's originating), but it doesn't catch anything.

The code is extremely simple (less than 10 lines per piece) maybe it would be easier if I sent it to you and we can continue this discussion off list.

thanks for the help, btw

sharkfish17-Oct-03 9:32

sharkfish

17-Oct-03 9:32

Is it possible to define an attribute that describes a property of a class at runtime?

For example, you have a class called "employee", and it has a property "name". The "name" property has an attribute that tells any calling code whether or not this property is "writable" and/or "readable", even though this property has both get/set accessors.

Maybe there is another way to do this, and I just don't have enough experience.

Any help is appreciated.

Re: custom attribute question

Alex Korchemniy17-Oct-03 10:49

Alex Korchemniy

17-Oct-03 10:49

For what you are trying to do, I suggest that you should try to avoid using attributes

Re: custom attribute question

sharkfish17-Oct-03 11:31

sharkfish

17-Oct-03 11:31

Is there a way to set a property of a property, at runtime, then?

This is what I REALLY want to do, but I believe this is not possible:

<br />
<br />
<br />
[AttributeUsage(AttributeTarget.Property,Inherited=true,AllowMultiple=true)]<br />
public class SecurityInfoAttribute : Attribute<br />
{<br />
  // Private Data<br />
  private int readable;<br />
  private int writable;<br />
<br />
<br />
  // Constructor<br />
  public SecurityInfoAttribute(int readable, int writable)<br />
  {<br />
    this.security_readable = 0;<br />
    this.security_writable = 0;<br />
<br />
  }<br />
<br />
  public int Readable<br />
  {<br />
    get<br />
    {<br />
      return readable;<br />
    }<br />
    set<br />
    {<br />
      readable = value;<br />
     }<br />
  }<br />
<br />
  public int Writable<br />
  {<br />
    get<br />
    {<br />
      return writable;<br />
    }<br />
    set<br />
    {<br />
       writable = value;<br />
    }<br />
  }<br />
<br />
<br />
}<br />
<br />
<br />
<br />
public class employee {<br />
<br />
string name;<br />
[SecurityInfo(getReadSecurityInfo(userId), getWriteSecurityInfo(userId))]<br />
string Name{get{return name;}set{name = value;}}<br />
<br />
<br />
<br />
} <br />

DataGrid and ArrayList

Wjousts17-Oct-03 8:26

Wjousts

17-Oct-03 8:26

I have a form which has a DataGrid which I bind to an ArrayList. The grid
displays fine and I can edit the values on the grid and they get passed on
to the objects in the ArrayList itself. The problem, however, is with
handling adding and remove objects from the ArrayList. It doesn't
automatically update the DataGrid to reflect the changes to the ArrayList.
So I tried this, which kind of works Confused | :confused:

private void btnNew_Click(object sender, System.EventArgs e)
{
    myAL.Add(new myClass());
    MyGrid.DataSource = null;
    MyGrid.DataSource = myAL;
}

private void btnDel_Click(object sender, System.EventArgs e)
{
    myAL.Remove(myAL[MyGrid.CurrentRowIndex]);
    MyGrid.CurrentRowIndex = 0;
    MyGrid.DataSource = null;
    MyGrid.DataSource = myAL;
}

This works until you try to either: remove the bottom item on the grid
(System.ArgumentOutOfRangeException) or add an item to an empty grid
(System.IndexOutOfRangeException). Plus it just doesn't seem like the right
way to do this. Can anybody help me out here and point me in the right
direction? Everything I've found online so far covers binding a grid to a
datatable or dataview only.

Re: DataGrid and ArrayList

Daniel M. Edwards17-Oct-03 16:59

Daniel M. Edwards

17-Oct-03 16:59

Why not bind to a dataset instead? Not sure it is the best method but if you want to stay with ArrayList try rebinding the datagrid, should "refresh" it.

Re: DataGrid and ArrayList

Heath Stewart18-Oct-03 10:49

Unrolling a loop: why can't .NET add 1 + 2 + 3 + ...

18-Oct-03 10:49

Actually, this is correct behavior, though not always desired.

Also, remember that the DataGrid acts no differently when binding to various data sources, like DataSet, DataTable, ArrayList, etc. If you look at the DataGrid's DataSource property, you'll see that it takes an Object that implements either IListSource, IList, or IEnumerable. It doesn't care much about the actual type.

So, any of those examples you've seen for other types will apply to the ArrayList.

One such method would be to get the CurrencyManager from the BindingContext of the DataGrid. You can receive event notification when the list changes and update the DataGrid either manually or by reassigning the list to the DataGrid.DataSource property (ps, you don't need to set it to null first).

MtnBiknGuy17-Oct-03 6:45

Re: Unrolling a loop: why can't .NET add 1 + 2 + 3 + ...

17-Oct-03 6:45

Take some standard code such as shown below. It simply loops to add up a
series of terms and it produces the correct result.

// sum numbers with a loop
public int DoSumLooping(int iterations)
{
int result = 0;
for(int i = 1;i <=iterations;i++)
{
result += i;
}
return result;
}

Now translate this into a specific solution that doesn't use looping (and
use the same value for the number of iterations the loop performs). This
code returns an incorrect result. The method consists entirely of a very
straightforward code statement, but in this case .NET adds the numbers
incorrectly.
public double ComputeSum( )
{
// Brute force sum method
// For iterations == 10000
double sum = 0+ 1+ 2+ 3+ 4+ 5+ 6+ 7+ 8+ 9+ 10+ 11+ 12+ 13+ 14+ 15+ ...
+ 9997+ 9998+ 9999+ 10000;
return sum;
}
The above method returns an incorrect result with any number of terms above
about 200. It will correctly add 1 + 2 + ... + 200, but it will NOT
correctly add 1 + 2 + ... + 1000.

I have just run across this, and I have not yet researched the possible
reasons for this behavior. It may be a known issue related to either stack
size or the length of a code line, but to my knowledge it hasn't been
discussed in any of the "popular" literature on C# and .NET. I need to write
code like this, so if anyone has already encountered this issue, please
advise me.

Here's another example that also creates problems, but of a somewhat
different nature. Take the following code and translate it into a specific,
non-looping method and try to execute it using reflection. It fails.

public double LoopToCompute()
{
double sumOfProducts = 0;
double grandTotal = 0;
for (int i = 0; i < maxRows; ++i)
{
for (int j = 0; j < maxCols; ++j)
{
sumOfProducts += coeff[j] * table[i][j];
}
a_point[i] = sumOfProducts;
grandTotal += sumOfProducts;
sumOfProducts = 0;
}
return grandTotal;
}//LoopToCompute

The above code works -- but it's equivalent code with loops unrolled (shown
below) doesn't work unless the maxRows is set very small. For small values,
the 2 methods (above and below) produce identical results. There is nothing
"wrong" with the code in that sense. It's similar to the above situation. If
the "size" of the code statement or the number of code statements is too
large, .NET fails. In this case (using reflection) it doesn't return the
incorrect result, as the first example did. In this case, reflection calls
it an invalid program and refuses to run it (but only when the value of
maxRows is above about 250). The reason for this is probably
straightforward. However, I have the need to make statements like this for
performance reasons so I need a work-around. Any suggestions are
appreciated! All comments are appreciated.

public double DoBruteForceCompute()
{
double bruteForceSum = 0;

point1=coeff1*table[0][0] +coeff2*table[0][1] +coeff3*table[0][2]
+coeff4*table[0][3] +coeff5*table[0][4] +coeff6*table[0][5]
+coeff7*table[0][6] +coeff8*table[0][7] +coeff9*table[0][8]
+coeff10*table[0][9] +coeff11*table[0][10] +coeff12*table[0][11]
+coeff13*table[0][12] +coeff14*table[0][13] +coeff15*table[0][14]
+coeff16*table[0][15] +coeff17*table[0][16] +coeff18*table[0][17]
+coeff19*table[0][18] +coeff20*table[0][19] +coeff21*table[0][20]
+coeff22*table[0][21] +coeff23*table[0][22] +coeff24*table[0][23]
+coeff25*table[0][24] +coeff26*table[0][25] +coeff27*table[0][26]
+coeff28*table[0][27] +coeff29*table[0][28] +coeff30*table[0][29]
+coeff31*table[0][30] +coeff32*table[0][31] +coeff33*table[0][32]
+coeff34*table[0][33] +coeff35*table[0][34] ;

point2=coeff1*table[1][0] +coeff2*table[1][1] +coeff3*table[1][2]
+coeff4*table[1][3] +coeff5*table[1][4] +coeff6*table[1][5]
+coeff7*table[1][6] +coeff8*table[1][7] +coeff9*table[1][8]
+coeff10*table[1][9] +coeff11*table[1][10] +coeff12*table[1][11]
+coeff13*table[1][12] +coeff14*table[1][13] +coeff15*table[1][14]
+coeff16*table[1][15] +coeff17*table[1][16] +coeff18*table[1][17]
+coeff19*table[1][18] +coeff20*table[1][19] +coeff21*table[1][20]
+coeff22*table[1][21] +coeff23*table[1][22] +coeff24*table[1][23]
+coeff25*table[1][24] +coeff26*table[1][25] +coeff27*table[1][26]
+coeff28*table[1][27] +coeff29*table[1][28] +coeff30*table[1][29]
+coeff31*table[1][30] +coeff32*table[1][31] +coeff33*table[1][32]
+coeff34*table[1][33] +coeff35*table[1][34] ;

[...]

point500=coeff1*table[499][0] +coeff2*table[499][1] +coeff3*table[499][2]
+coeff4*table[499][3] +coeff5*table[499][4] +coeff6*table[499][5]
+coeff7*table[499][6] +coeff8*table[499][7] +coeff9*table[499][8]
+coeff10*table[499][9] +coeff11*table[499][10] +coeff12*table[499][11]
+coeff13*table[499][12] +coeff14*table[499][13] +coeff15*table[499][14]
+coeff16*table[499][15] +coeff17*table[499][16] +coeff18*table[499][17]
+coeff19*table[499][18] +coeff20*table[499][19] +coeff21*table[499][20]
+coeff22*table[499][21] +coeff23*table[499][22] +coeff24*table[499][23]
+coeff25*table[499][24] +coeff26*table[499][25] +coeff27*table[499][26]
+coeff28*table[499][27] +coeff29*table[499][28] +coeff30*table[499][29]
+coeff31*table[499][30] +coeff32*table[499][31] +coeff33*table[499][32]
+coeff34*table[499][33] +coeff35*table[499][34] ;

bruteForceSum =
point1 +
point2 + ... +

point499 +
point500
;

return bruteForceSum;

}//DoBruteForceCompute

Daniel Turini17-Oct-03 7:08

Daniel Turini

17-Oct-03 7:08

I'd suggest you to use ILDASM and see the generated code. This will help to isolate if the problem is on JIT or on C# compiler. Also, you could try using other .NET languages, like VB.NET.
BTW, for this kind of code, managed C++ rules. With C++ you always have much more control over the compiler.

Help me dominate the world - click this link and my army will grow

Re: Unrolling a loop: why can't .NET add 1 + 2 + 3 + ...

leppie17-Oct-03 9:33

leppie

17-Oct-03 9:33

Interesting situation Smile | :)

What version of .NET are u using? Are you going over the 2048 character line limit?

The did the same thing, but with a single " + xxxx" on a single line and get the proper result (50005000 for 10000). In fact the compiler does constant folding and only loads the result.

leppie ::AllocCPArticle("Zee blog");
Seen on my Campus BBS: Linux is free...coz no-one wants to pay for it.

Re: Unrolling a loop: why can't .NET add 1 + 2 + 3 + ...

MtnBiknGuy17-Oct-03 16:18

Re: Unrolling a loop: why can't .NET add 1 + 2 + 3 + ...

17-Oct-03 16:18

I found the problem. I think you could have guessed it -- it was related to the line limit. Here's what I was doing. I was using code to generate my unrolled loop code. I was then compiling this in a process and using reflection to load the assembly and invoke the method.

I was not getting any compiler errors, nor was I getting any runtime errors. I was just getting incorrect math results.

However, when I posted the code (without the reflection part) everyone else got the correct results. This prompted me to look at the reflection/compilation code more closely. It turns out the when I pasted the generated code into the IDE I discovered the line limit you mentioned.

I inserted a new line in my generated code after every 200 terms, and presto- the math results were now correct.

It's a bit disconcerting that I didn't get a compiler error from the command line compiler. I don't know why yet. Does the command line compiler have that same line limit? I assume so, given my experience.

I guess the compiler just took as many terms as it could and somehow terminated the statement and produced a runnable program ... all very strange. I wouldn't have thought that possible.

Anonymous17-Oct-03 18:24

Anonymous

17-Oct-03 18:24

It's working with DotGNU anyway ... Log a bug with MS

Re: Unrolling a loop: why can't .NET add 1 + 2 + 3 + ...

MtnBiknGuy18-Oct-03 3:55

Re: Unrolling a loop: why can't .NET add 1 + 2 + 3 + ...

18-Oct-03 3:55

leppie,
Do you happen to know why the following method "is not a valid program"? It compiles fine, but the runtime won't even try to run it. It contains 500 statements (I cut out 497 of them for this post) like those below. The method represents another unrolled loop. (And this is the one I mentioned that is actually 5-10 times slower than the loop after it's unrolled.) I appreciate any comments.
Dave
P.S. I forgot to mention that the problem is related to the number of statements in the method. 1000 doesn't work. I think it works up to a few hundred statements, then stops being "a valid program."

public double DoBruteForceCompute()
{
double bruteForceSum = 0;

point1=coeff1*table[0][0] +coeff2*table[0][1] +coeff3*table[0][2]
+coeff4*table[0][3] +coeff5*table[0][4] +coeff6*table[0][5]
+coeff7*table[0][6] +coeff8*table[0][7] +coeff9*table[0][8]
+coeff10*table[0][9] +coeff11*table[0][10] +coeff12*table[0][11]
+coeff13*table[0][12] +coeff14*table[0][13] +coeff15*table[0][14]
+coeff16*table[0][15] +coeff17*table[0][16] +coeff18*table[0][17]
+coeff19*table[0][18] +coeff20*table[0][19] +coeff21*table[0][20]
+coeff22*table[0][21] +coeff23*table[0][22] +coeff24*table[0][23]
+coeff25*table[0][24] +coeff26*table[0][25] +coeff27*table[0][26]
+coeff28*table[0][27] +coeff29*table[0][28] +coeff30*table[0][29]
+coeff31*table[0][30] +coeff32*table[0][31] +coeff33*table[0][32]
+coeff34*table[0][33] +coeff35*table[0][34] ;

point2=coeff1*table[1][0] +coeff2*table[1][1] +coeff3*table[1][2]
+coeff4*table[1][3] +coeff5*table[1][4] +coeff6*table[1][5]
+coeff7*table[1][6] +coeff8*table[1][7] +coeff9*table[1][8]
+coeff10*table[1][9] +coeff11*table[1][10] +coeff12*table[1][11]
+coeff13*table[1][12] +coeff14*table[1][13] +coeff15*table[1][14]
+coeff16*table[1][15] +coeff17*table[1][16] +coeff18*table[1][17]
+coeff19*table[1][18] +coeff20*table[1][19] +coeff21*table[1][20]
+coeff22*table[1][21] +coeff23*table[1][22] +coeff24*table[1][23]
+coeff25*table[1][24] +coeff26*table[1][25] +coeff27*table[1][26]
+coeff28*table[1][27] +coeff29*table[1][28] +coeff30*table[1][29]
+coeff31*table[1][30] +coeff32*table[1][31] +coeff33*table[1][32]
+coeff34*table[1][33] +coeff35*table[1][34] ;

[...]

point500=coeff1*table[499][0] +coeff2*table[499][1] +coeff3*table[499][2]
+coeff4*table[499][3] +coeff5*table[499][4] +coeff6*table[499][5]
+coeff7*table[499][6] +coeff8*table[499][7] +coeff9*table[499][8]
+coeff10*table[499][9] +coeff11*table[499][10] +coeff12*table[499][11]
+coeff13*table[499][12] +coeff14*table[499][13] +coeff15*table[499][14]
+coeff16*table[499][15] +coeff17*table[499][16] +coeff18*table[499][17]
+coeff19*table[499][18] +coeff20*table[499][19] +coeff21*table[499][20]
+coeff22*table[499][21] +coeff23*table[499][22] +coeff24*table[499][23]
+coeff25*table[499][24] +coeff26*table[499][25] +coeff27*table[499][26]
+coeff28*table[499][27] +coeff29*table[499][28] +coeff30*table[499][29]
+coeff31*table[499][30] +coeff32*table[499][31] +coeff33*table[499][32]
+coeff34*table[499][33] +coeff35*table[499][34] ;

bruteForceSum =
point1 +
point2 + ... +
point500
;

return bruteForceSum;

}//DoBruteForceCompute

MtnBiknGuy20-Oct-03 14:15