Async DIME call seem to drop randomly

[Bob]

I have a web service using WSE 1.0SP DIME attachment to transfer files in
production. The synchronous call works great and pretty stable. I have
been trying to add the asyncrhonous calls. On the surface it works but then
I realized that when multiple async calls are made to the server in a loop,
some callbacks never happen (no exception either). Here's a piece of
simplified test code on the client side (Windows app) below. Everytime the
button click event is fired, anywhere from 1 to all the files may be
transferred. I'm suspecting some of the callbacks are colliding but don't
know how to check.

........................
private AsyncDime _svc; //AsyncDime is the WS proxy class.

//Windows Form button click event handler, this starts the async file
get process.
//This test trys to get 4 files from the server by giving the file
names.
private void btnGetFileAsync_Click(object sender, System.EventArgs e) {
string[] fns = new string[] {"BobTestFile.txt", "BobTestFile1.txt",
"BobTestFile2.txt", "BobTestFile3.txt"};
this._svc = new AsyncDime();
foreach (string fn in fns) {
AsyncCallback acb = new
AsyncCallback(this.RetrievalDoneCallback);
this._svc.BeginGetFile(fn, acb, this._svc);
}
}

//Handles the call back.
private void RetrievalDoneCallback(IAsyncResult returnValue) {
AsyncDime fileService = (AsyncDime)returnValue.AsyncState;
fileService.EndGetFile(returnValue);
string fileNameFrAttachment =
this.SaveAttachment(fileService.ResponseSoapContext.Attachments[0]);
}

//Save the attachement to a file
private string SaveAttachment(DimeAttachment da) {
int len;
byte[] chunk = new Byte[256];
System.IO.FileStream fs;
System.IO.Stream st;
string fileName = da.Id;
st = da.Stream;
fs = File.Open( @"c:\temp\" + fileName, FileMode.OpenOrCreate,
FileAccess.Write);
while ((len = st.Read(chunk, 0, chunk.Length)) > 0) {
fs.Write(chunk, 0, len);
}
st.Close();
fs.Close();
return fileName;
}

 

[Govind Ramanathan]

Hi Bob,
What is the effect you are seeing? The SaveAttachment method is not thread
safe. It might be a problem with that. How did you figure out that the
recalls didn't happen? Please provide some more information.


Govind

 

[Bob]

When I was doing testing I noticed some files are not saved to the file
system on the client side (that is, out of the 4 files, only 2 or 3 show up
in the result folder), and it seems random which files are not saved.

Could you provide a bit more detail on why the SaveAttachment() method is
not thread-safe and what can be done to make it so? I did notice that the
very first file transferred to the client side ends up being used by some
process (so it can be copied or moved) for a while. That may have something
to do with what you are saying.

Thanks for the help
Bob

Hi Bob,
What is the effect you are seeing? The SaveAttachment method is not thread
safe. It might be a problem with that. How did you figure out that the
recalls didn't happen? Please provide some more information.


Govind

I have a web service using WSE 1.0SP DIME attachment to transfer files in
production. The synchronous call works great and pretty stable. I have
been trying to add the asyncrhonous calls. On the surface it works but then
I realized that when multiple async calls are made to the server in a loop,
some callbacks never happen (no exception either). Here's a piece of
simplified test code on the client side (Windows app) below. Everytime the
button click event is fired, anywhere from 1 to all the files may be
transferred. I'm suspecting some of the callbacks are colliding but don't
know how to check.

........................
private AsyncDime _svc; //AsyncDime is the WS proxy class.

//Windows Form button click event handler, this starts the async file
get process.
//This test trys to get 4 files from the server by giving the file
names.
private void btnGetFileAsync_Click(object sender, System.EventArgs

e)

{
string[] fns = new string[] {"BobTestFile.txt", "BobTestFile1.txt",
"BobTestFile2.txt", "BobTestFile3.txt"};
this._svc = new AsyncDime();
foreach (string fn in fns) {
AsyncCallback acb = new
AsyncCallback(this.RetrievalDoneCallback);
this._svc.BeginGetFile(fn, acb, this._svc);
}
}

//Handles the call back.
private void RetrievalDoneCallback(IAsyncResult returnValue) {
AsyncDime fileService = (AsyncDime)returnValue.AsyncState;
fileService.EndGetFile(returnValue);
string fileNameFrAttachment =
this.SaveAttachment(fileService.ResponseSoapContext.Attachments[0]);
}

//Save the attachement to a file
private string SaveAttachment(DimeAttachment da) {
int len;
byte[] chunk = new Byte[256];
System.IO.FileStream fs;
System.IO.Stream st;
string fileName = da.Id;
st = da.Stream;
fs = File.Open( @"c:\temp\" + fileName, FileMode.OpenOrCreate,
FileAccess.Write);
while ((len = st.Read(chunk, 0, chunk.Length)) > 0) {
fs.Write(chunk, 0, len);
}
st.Close();
fs.Close();
return fileName;
}

 

[Byron Kim]

This is thread safety issue. You should use separate proxy in calling each
asynchronous call.

thanks
Byron KIM

 

[Bob]

Hmm, I think you are right. Thanks a lot. I changed the moved the code to
create the proxy into the loop so everytime it's a new instance. I tried a
few times and everytime it's getting all the files. So the new code to
begin the call is below. The async call is not very efficient then. If I
have a very large number of files, it would end up creating so many
instances.

private void btnGetFileAsync_Click(object sender, System.EventArgs e) {
string[] fns = new string[] {"BobTestFile.txt",
"BobTestFile1.txt","BobTestFile2.txt", "BobTestFile3.txt"};
foreach (string fn in fns) {
AsyncCallback acb = new
AsyncCallback(this.RetrievalDoneCallback);
this._svc = new AsyncDime();
this._svc.BeginGetFile(fn, acb, this._svc);
}
}

This is thread safety issue. You should use separate proxy in calling each
asynchronous call.

thanks
Byron KIM

I have a web service using WSE 1.0SP DIME attachment to transfer files in
production. The synchronous call works great and pretty stable. I have
been trying to add the asyncrhonous calls. On the surface it works but then
I realized that when multiple async calls are made to the server in a loop,
some callbacks never happen (no exception either). Here's a piece of
simplified test code on the client side (Windows app) below. Everytime the
button click event is fired, anywhere from 1 to all the files may be
transferred. I'm suspecting some of the callbacks are colliding but don't
know how to check.

........................
private AsyncDime _svc; //AsyncDime is the WS proxy class.

//Windows Form button click event handler, this starts the async file
get process.
//This test trys to get 4 files from the server by giving the file
names.
private void btnGetFileAsync_Click(object sender, System.EventArgs

e)

{
string[] fns = new string[] {"BobTestFile.txt", "BobTestFile1.txt",
"BobTestFile2.txt", "BobTestFile3.txt"};
this._svc = new AsyncDime();
foreach (string fn in fns) {
AsyncCallback acb = new
AsyncCallback(this.RetrievalDoneCallback);
this._svc.BeginGetFile(fn, acb, this._svc);
}
}

//Handles the call back.
private void RetrievalDoneCallback(IAsyncResult returnValue) {
AsyncDime fileService = (AsyncDime)returnValue.AsyncState;
fileService.EndGetFile(returnValue);
string fileNameFrAttachment =
this.SaveAttachment(fileService.ResponseSoapContext.Attachments[0]);
}

//Save the attachement to a file
private string SaveAttachment(DimeAttachment da) {
int len;
byte[] chunk = new Byte[256];
System.IO.FileStream fs;
System.IO.Stream st;
string fileName = da.Id;
st = da.Stream;
fs = File.Open( @"c:\temp\" + fileName, FileMode.OpenOrCreate,
FileAccess.Write);
while ((len = st.Read(chunk, 0, chunk.Length)) > 0) {
fs.Write(chunk, 0, len);
}
st.Close();
fs.Close();
return fileName;
}