HttpModule multithreading and request and response corelation

Discussion in 'ASP .Net' started by =?Utf-8?B?U2hhcGlybw==?=, Dec 7, 2004.

  1. I have a scenario where I log a resquest to a database table and update the
    request with a corresponding response including the response time. I am using
    an HttpModule to do this.

    My challenge is how to corelate the response to a corresponding request. I
    am looking for a sure proof threadsafe way to corelate a response to a
    coresponding request message.


    Two things that concerns me:-

    1. I am using the onBeginRequest event to capture the request and persist it
    in the database and a filter class inheriting from the stream class to
    capture the response and update a request row in the database with the
    correspond response using an Id I generate to correct the messages.

    2. My question is that if I create a guid in the onBeginRequest method and
    pass it as a parameter to the filter class will this work from correlation
    and multithreading standpoint since the messgae Id is a private memebr
    variable in the filter class and is accessed by the overriden write method?

    sample code

    private void OnBeginRequest( object sender, EventArgs args )
    {
    string requestContent = string.Empty;

    // HttpApplication httpApp = sender as HttpApplication;

    // current request context
    HttpContext context = HttpContext.Current;

    // long position = httpApp.Context.Request.InputStream.Position;
    long position = context.Request.InputStream.Position;

    // Stream requestStream = httpApp.Context.Request.InputStream;

    Stream requestStream = context.Request.InputStream;

    byte[] buffer = new byte[ requestStream.Length ];

    int read = requestStream.Read( buffer, 0, (int)requestStream.Length
    );

    //reset the stream to the original position
    // httpApp.Request.InputStream.Position = position;

    context.Request.InputStream.Position = position;

    requestContent = System.Web.HttpUtility.HtmlDecode(
    System.Web.HttpUtility.UrlDecode(System.Text.Encoding.Default.GetString(
    buffer ) ));

    if( requestContent.Length == 0 ) return;

    //generate message Id to corelate the request and resoponse
    string messageId = System.Guid.NewGuid().ToString();

    // For Get and Http posts remove the name from the name/value pair
    requestContent = requestContent.Substring( requestContent.IndexOf( "=<" ) +
    1 );

    // append the messageId to the message
    requestContent = requestContent.Insert( requestContent.LastIndexOf("/") - 1,
    "<messageId>" + messageId + "</messageId>" );

    LogRequestInfo( requestContent );

    // apply the filter to access the response stream
    // _responseStream = new ResponseStream( _httpApp.Response.Filter );

    // httpApp.Context.Response.Filter = new ResponseStream(
    HttpContext.Current.Response.Filter, messageId );
    _responseStream = new ResponseStream( context.Response.Filter, messageId );
    context.Response.Filter = _responseStream;

    }


    The critical question here is that there is very little documentation from
    Microsoft on threading issues regarding use of httpmodules and how the
    httpmodule instances are created and used.

    sample filter class code

    public sealed class ResponseStream : Stream
    {
    private Stream _responseStream;
    private string _messageId;

    public ResponseStream( Stream sink )
    {
    _responseStream = sink;
    }

    public ResponseStream( Stream sink, string messageId )
    {
    _responseStream = sink;
    _messageId = messageId;
    }

    public override void Write( byte[] buffer, int offset, int count )
    {
    _responseStream.Write( buffer, offset, count );

    // get the response string from the byte stream
    string responseString = System.Web.HttpUtility.HtmlDecode(
    System.Web.HttpUtility.UrlDecode(Encoding.Default.GetString( buffer ).Trim()
    ) );

    //append the message Id to the response message
    responseString = responseString.Insert( responseString.LastIndexOf("/") - 1,
    "<messageId>" + _messageId + "</messageId>" );

    // log the response
    LogResponseInfo( responseString );
    }


    Thanks for your help in advance.
    SOA Freak
    =?Utf-8?B?U2hhcGlybw==?=, Dec 7, 2004
    #1
    1. Advertising

  2. =?Utf-8?B?U2hhcGlybw==?=

    Scott Allen Guest

    Hi Shapiro:

    I'm a little confused by the question, so I apologize in advance if
    this answer is not what you are looking for.

    If you are trying to tie together a logical thread of execution among
    various modules and filters, one place to keep state about the
    response is in the Context.Items collection. This contents of the
    collection are only around for the duration of a request response. You
    could plop in an ID here that you get back when logging the request,
    and retrieve it to know what record to update later on.

    --
    Scott
    http://www.OdeToCode.com/blogs/scott/


    On Mon, 6 Dec 2004 16:57:02 -0800, "Shapiro"
    <> wrote:

    > I have a scenario where I log a resquest to a database table and update the
    >request with a corresponding response including the response time. I am using
    >an HttpModule to do this.
    >
    >My challenge is how to corelate the response to a corresponding request. I
    >am looking for a sure proof threadsafe way to corelate a response to a
    >coresponding request message.
    >
    >
    >Two things that concerns me:-
    >
    >1. I am using the onBeginRequest event to capture the request and persist it
    >in the database and a filter class inheriting from the stream class to
    >capture the response and update a request row in the database with the
    >correspond response using an Id I generate to correct the messages.
    >
    >2. My question is that if I create a guid in the onBeginRequest method and
    >pass it as a parameter to the filter class will this work from correlation
    >and multithreading standpoint since the messgae Id is a private memebr
    >variable in the filter class and is accessed by the overriden write method?
    >
    >sample code
    >
    >private void OnBeginRequest( object sender, EventArgs args )
    >{
    >string requestContent = string.Empty;
    >
    >// HttpApplication httpApp = sender as HttpApplication;
    >
    >// current request context
    >HttpContext context = HttpContext.Current;
    >
    >// long position = httpApp.Context.Request.InputStream.Position;
    >long position = context.Request.InputStream.Position;
    >
    >// Stream requestStream = httpApp.Context.Request.InputStream;
    >
    >Stream requestStream = context.Request.InputStream;
    >
    >byte[] buffer = new byte[ requestStream.Length ];
    >
    > int read = requestStream.Read( buffer, 0, (int)requestStream.Length
    >);
    >
    >//reset the stream to the original position
    >// httpApp.Request.InputStream.Position = position;
    >
    >context.Request.InputStream.Position = position;
    >
    > requestContent = System.Web.HttpUtility.HtmlDecode(
    >System.Web.HttpUtility.UrlDecode(System.Text.Encoding.Default.GetString(
    >buffer ) ));
    >
    >if( requestContent.Length == 0 ) return;
    >
    >//generate message Id to corelate the request and resoponse
    >string messageId = System.Guid.NewGuid().ToString();
    >
    >// For Get and Http posts remove the name from the name/value pair
    >requestContent = requestContent.Substring( requestContent.IndexOf( "=<" ) +
    >1 );
    >
    >// append the messageId to the message
    >requestContent = requestContent.Insert( requestContent.LastIndexOf("/") - 1,
    >"<messageId>" + messageId + "</messageId>" );
    >
    >LogRequestInfo( requestContent );
    >
    >// apply the filter to access the response stream
    >// _responseStream = new ResponseStream( _httpApp.Response.Filter );
    >
    >// httpApp.Context.Response.Filter = new ResponseStream(
    >HttpContext.Current.Response.Filter, messageId );
    >_responseStream = new ResponseStream( context.Response.Filter, messageId );
    >context.Response.Filter = _responseStream;
    >
    >}
    >
    >
    >The critical question here is that there is very little documentation from
    >Microsoft on threading issues regarding use of httpmodules and how the
    >httpmodule instances are created and used.
    >
    >sample filter class code
    >
    >public sealed class ResponseStream : Stream
    >{
    >private Stream _responseStream;
    >private string _messageId;
    >
    >public ResponseStream( Stream sink )
    >{
    >_responseStream = sink;
    >}
    >
    >public ResponseStream( Stream sink, string messageId )
    >{
    >_responseStream = sink;
    >_messageId = messageId;
    >}
    >
    >public override void Write( byte[] buffer, int offset, int count )
    >{
    >_responseStream.Write( buffer, offset, count );
    >
    >// get the response string from the byte stream
    >string responseString = System.Web.HttpUtility.HtmlDecode(
    >System.Web.HttpUtility.UrlDecode(Encoding.Default.GetString( buffer ).Trim()
    >) );
    >
    >//append the message Id to the response message
    >responseString = responseString.Insert( responseString.LastIndexOf("/") - 1,
    >"<messageId>" + _messageId + "</messageId>" );
    >
    >// log the response
    >LogResponseInfo( responseString );
    >}
    >
    >
    >Thanks for your help in advance.
    >SOA Freak
    Scott Allen, Dec 7, 2004
    #2
    1. Advertising

  3. Scott,

    The Context.Items collection is not available in the filter class. I am
    overridding the write method. My sample code is showing what I am trying to
    achive.


    Regards,
    Shepard

    "Scott Allen" wrote:

    > Hi Shapiro:
    >
    > I'm a little confused by the question, so I apologize in advance if
    > this answer is not what you are looking for.
    >
    > If you are trying to tie together a logical thread of execution among
    > various modules and filters, one place to keep state about the
    > response is in the Context.Items collection. This contents of the
    > collection are only around for the duration of a request response. You
    > could plop in an ID here that you get back when logging the request,
    > and retrieve it to know what record to update later on.
    >
    > --
    > Scott
    > http://www.OdeToCode.com/blogs/scott/
    >
    >
    > On Mon, 6 Dec 2004 16:57:02 -0800, "Shapiro"
    > <> wrote:
    >
    > > I have a scenario where I log a resquest to a database table and update the
    > >request with a corresponding response including the response time. I am using
    > >an HttpModule to do this.
    > >
    > >My challenge is how to corelate the response to a corresponding request. I
    > >am looking for a sure proof threadsafe way to corelate a response to a
    > >coresponding request message.
    > >
    > >
    > >Two things that concerns me:-
    > >
    > >1. I am using the onBeginRequest event to capture the request and persist it
    > >in the database and a filter class inheriting from the stream class to
    > >capture the response and update a request row in the database with the
    > >correspond response using an Id I generate to correct the messages.
    > >
    > >2. My question is that if I create a guid in the onBeginRequest method and
    > >pass it as a parameter to the filter class will this work from correlation
    > >and multithreading standpoint since the messgae Id is a private memebr
    > >variable in the filter class and is accessed by the overriden write method?
    > >
    > >sample code
    > >
    > >private void OnBeginRequest( object sender, EventArgs args )
    > >{
    > >string requestContent = string.Empty;
    > >
    > >// HttpApplication httpApp = sender as HttpApplication;
    > >
    > >// current request context
    > >HttpContext context = HttpContext.Current;
    > >
    > >// long position = httpApp.Context.Request.InputStream.Position;
    > >long position = context.Request.InputStream.Position;
    > >
    > >// Stream requestStream = httpApp.Context.Request.InputStream;
    > >
    > >Stream requestStream = context.Request.InputStream;
    > >
    > >byte[] buffer = new byte[ requestStream.Length ];
    > >
    > > int read = requestStream.Read( buffer, 0, (int)requestStream.Length
    > >);
    > >
    > >//reset the stream to the original position
    > >// httpApp.Request.InputStream.Position = position;
    > >
    > >context.Request.InputStream.Position = position;
    > >
    > > requestContent = System.Web.HttpUtility.HtmlDecode(
    > >System.Web.HttpUtility.UrlDecode(System.Text.Encoding.Default.GetString(
    > >buffer ) ));
    > >
    > >if( requestContent.Length == 0 ) return;
    > >
    > >//generate message Id to corelate the request and resoponse
    > >string messageId = System.Guid.NewGuid().ToString();
    > >
    > >// For Get and Http posts remove the name from the name/value pair
    > >requestContent = requestContent.Substring( requestContent.IndexOf( "=<" ) +
    > >1 );
    > >
    > >// append the messageId to the message
    > >requestContent = requestContent.Insert( requestContent.LastIndexOf("/") - 1,
    > >"<messageId>" + messageId + "</messageId>" );
    > >
    > >LogRequestInfo( requestContent );
    > >
    > >// apply the filter to access the response stream
    > >// _responseStream = new ResponseStream( _httpApp.Response.Filter );
    > >
    > >// httpApp.Context.Response.Filter = new ResponseStream(
    > >HttpContext.Current.Response.Filter, messageId );
    > >_responseStream = new ResponseStream( context.Response.Filter, messageId );
    > >context.Response.Filter = _responseStream;
    > >
    > >}
    > >
    > >
    > >The critical question here is that there is very little documentation from
    > >Microsoft on threading issues regarding use of httpmodules and how the
    > >httpmodule instances are created and used.
    > >
    > >sample filter class code
    > >
    > >public sealed class ResponseStream : Stream
    > >{
    > >private Stream _responseStream;
    > >private string _messageId;
    > >
    > >public ResponseStream( Stream sink )
    > >{
    > >_responseStream = sink;
    > >}
    > >
    > >public ResponseStream( Stream sink, string messageId )
    > >{
    > >_responseStream = sink;
    > >_messageId = messageId;
    > >}
    > >
    > >public override void Write( byte[] buffer, int offset, int count )
    > >{
    > >_responseStream.Write( buffer, offset, count );
    > >
    > >// get the response string from the byte stream
    > >string responseString = System.Web.HttpUtility.HtmlDecode(
    > >System.Web.HttpUtility.UrlDecode(Encoding.Default.GetString( buffer ).Trim()
    > >) );
    > >
    > >//append the message Id to the response message
    > >responseString = responseString.Insert( responseString.LastIndexOf("/") - 1,
    > >"<messageId>" + _messageId + "</messageId>" );
    > >
    > >// log the response
    > >LogResponseInfo( responseString );
    > >}
    > >
    > >
    > >Thanks for your help in advance.
    > >SOA Freak

    >
    >
    =?Utf-8?B?U2hhcGlybw==?=, Dec 7, 2004
    #3
  4. =?Utf-8?B?U2hhcGlybw==?=

    Scott Allen Guest

    Have you tried using HttpContext.Current to retrieve the current
    context and get to the Item collection from inside the filter class?
    There has to be a context, or you would not be able to respond to the
    request.

    --
    Scott
    http://www.OdeToCode.com/blogs/scott/


    On Tue, 7 Dec 2004 10:39:04 -0800, "Shapiro"
    <> wrote:

    >Scott,
    >
    >The Context.Items collection is not available in the filter class. I am
    >overridding the write method. My sample code is showing what I am trying to
    >achive.
    >
    >
    >Regards,
    >Shepard
    >
    Scott Allen, Dec 7, 2004
    #4
  5. Thats one route. I guess my questions are that how the httpmodules are
    instantiated and handled in multithreading and wether what I an doing in the
    code is correct. I have provided sample code for review.


    "Scott Allen" wrote:

    > Have you tried using HttpContext.Current to retrieve the current
    > context and get to the Item collection from inside the filter class?
    > There has to be a context, or you would not be able to respond to the
    > request.
    >
    > --
    > Scott
    > http://www.OdeToCode.com/blogs/scott/
    >
    >
    > On Tue, 7 Dec 2004 10:39:04 -0800, "Shapiro"
    > <> wrote:
    >
    > >Scott,
    > >
    > >The Context.Items collection is not available in the filter class. I am
    > >overridding the write method. My sample code is showing what I am trying to
    > >achive.
    > >
    > >
    > >Regards,
    > >Shepard
    > >

    >
    >
    =?Utf-8?B?U2hhcGlybw==?=, Dec 7, 2004
    #5
  6. =?Utf-8?B?U2hhcGlybw==?=

    Scott Allen Guest

    Each instance of the HttpApplication class will create the HttpModules
    needed (and registered in web.config).

    HttpApplication objects (despite what the name implies) are pooled by
    the ASP.NET runtime, so there is more than one. For each incoming
    request an instance of HttpApplication is taken from the free pool and
    assigned to service the request.

    This means an HttpModule will service only one request at a time, but
    it's still dangerous to keep state around in the class, because they
    are pooled and reused across requests.

    I agree, it's not well doc'ed. This knownledge is based on
    experimentation and the Reflector tool.

    --
    Scott
    http://www.OdeToCode.com/blogs/scott/


    On Tue, 7 Dec 2004 11:47:09 -0800, "Shapiro"
    <> wrote:

    >Thats one route. I guess my questions are that how the httpmodules are
    >instantiated and handled in multithreading and wether what I an doing in the
    >code is correct. I have provided sample code for review.
    >
    >
    >"Scott Allen" wrote:
    >
    >> Have you tried using HttpContext.Current to retrieve the current
    >> context and get to the Item collection from inside the filter class?
    >> There has to be a context, or you would not be able to respond to the
    >> request.
    >>
    >> --
    >> Scott
    >> http://www.OdeToCode.com/blogs/scott/
    >>
    >>
    >> On Tue, 7 Dec 2004 10:39:04 -0800, "Shapiro"
    >> <> wrote:
    >>
    >> >Scott,
    >> >
    >> >The Context.Items collection is not available in the filter class. I am
    >> >overridding the write method. My sample code is showing what I am trying to
    >> >achive.
    >> >
    >> >
    >> >Regards,
    >> >Shepard
    >> >

    >>
    >>
    Scott Allen, Dec 7, 2004
    #6
  7. Scott,

    Thanks for the reply but you have not answered my question. Looking at the
    sample code and the description of the issue I have at hand will that work?

    Regards,
    Shapiro
    "Shapiro" wrote:

    > Thats one route. I guess my questions are that how the httpmodules are
    > instantiated and handled in multithreading and wether what I an doing in the
    > code is correct. I have provided sample code for review.
    >
    >
    > "Scott Allen" wrote:
    >
    > > Have you tried using HttpContext.Current to retrieve the current
    > > context and get to the Item collection from inside the filter class?
    > > There has to be a context, or you would not be able to respond to the
    > > request.
    > >
    > > --
    > > Scott
    > > http://www.OdeToCode.com/blogs/scott/
    > >
    > >
    > > On Tue, 7 Dec 2004 10:39:04 -0800, "Shapiro"
    > > <> wrote:
    > >
    > > >Scott,
    > > >
    > > >The Context.Items collection is not available in the filter class. I am
    > > >overridding the write method. My sample code is showing what I am trying to
    > > >achive.
    > > >
    > > >
    > > >Regards,
    > > >Shepard
    > > >

    > >
    > >
    =?Utf-8?B?U2hhcGlybw==?=, Dec 7, 2004
    #7
  8. =?Utf-8?B?U2hhcGlybw==?=

    Scott Allen Guest

    I guess I'm not sure what exactly the question is, my apologies.
    The code seems ok, but only testing will tell :)

    --
    Scott
    http://www.OdeToCode.com/blogs/scott/

    On Tue, 7 Dec 2004 15:37:02 -0800, "Shapiro"
    <> wrote:

    >Scott,
    >
    > Thanks for the reply but you have not answered my question. Looking at the
    >sample code and the description of the issue I have at hand will that work?
    >
    >Regards,
    >Shapiro
    >"Shapiro" wrote:
    >
    >> Thats one route. I guess my questions are that how the httpmodules are
    >> instantiated and handled in multithreading and wether what I an doing in the
    >> code is correct. I have provided sample code for review.
    >>
    >>
    >> "Scott Allen" wrote:
    >>
    >> > Have you tried using HttpContext.Current to retrieve the current
    >> > context and get to the Item collection from inside the filter class?
    >> > There has to be a context, or you would not be able to respond to the
    >> > request.
    >> >
    >> > --
    >> > Scott
    >> > http://www.OdeToCode.com/blogs/scott/
    >> >
    >> >
    >> > On Tue, 7 Dec 2004 10:39:04 -0800, "Shapiro"
    >> > <> wrote:
    >> >
    >> > >Scott,
    >> > >
    >> > >The Context.Items collection is not available in the filter class. I am
    >> > >overridding the write method. My sample code is showing what I am trying to
    >> > >achive.
    >> > >
    >> > >
    >> > >Regards,
    >> > >Shepard
    >> > >
    >> >
    >> >
    Scott Allen, Dec 8, 2004
    #8
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