Threadsafe WebService log

[blondebier]

Hi Guys,

I have a vb.net WebService that has recently started getting very busy. This is good, but we now realise that the activity/error logging class that we have is not suitable as it is not thread safe.

This is an example of my Activity Log.

06/11/2007 14:38:55 LIVE: Start CheckAddress WebMethod ****************************************************************
06/11/2007 14:38:55 LIVE: XML Recieved to CheckAddress
06/11/2007 14:38:55 LIVE: <?xml version="1.0" encoding="utf-8"?><CheckAddress><ClientID>username</ClientID><ClientPWD>secret</ClientPWD><Address><HouseNumber>1</HouseNumber><Street>Toy Street</Street><District /><Town>Toy Town</Town><County>My County</County><Postcode>PC1 1CD</Postcode><AtAddressFrom>01/01/2003</AtAddressFrom><AtAddressTo>01/01/2006</AtAddressTo><AddressType>U</AddressType></Address></CheckAddress>
06/11/2007 14:38:56 LIVE: UserID: 1
06/11/2007 14:38:57 LIVE: Validating the address...
06/11/2007 14:38:57 LIVE: Validation complete. Final XML response...
06/11/2007 14:38:57 LIVE: <?xml version="1.0" encoding="UTF-8"?><Result>AddressOK</Result>
06/11/2007 14:38:57 LIVE: End CheckAddress WebMethod ****************************************************************

This is fine when requests come in one at a time, but if 2 or more requests are received by the web service at the same time or very close together, the Activity log entries get mixed up and I can't see what is going on.

I have a module in my project as follows:

Module _Module

Public Sub dBug(ByVal Narrative As String)
Dim log As New ErrorLog
Dim debug As Boolean
Dim environment As String = ""

Try
debug = CType(ConfigurationManager.AppSettings("Debug"), Boolean)
environment = ConfigurationManager.AppSettings("Environment")

' Only write to the error log if debugging is enabled
If debug Then
If Narrative = "" Then
log.WriteError("X")
Else
log.WriteError("Log " & Now & " " & environment & ": " & Narrative)
End If
End If

Catch sii As System.IO.IOException
Try
log.WriteError("Log " & Now & " " & environment & ": " & Narrative)
Catch ex As Exception
' Do Nothing
End Try
Catch ex As Exception
' Do Nothing
End Try

End Sub

End Module

I can then reference the dbug() function wherever I need to in my WebService for writing debug statements.

My ErrorLog class is as follows:

Public Class ErrorLog

Public Sub WriteError(ByVal ErrorMessage As String, Optional ByVal FilePath As String = "C:\")
Dim LogPath, environment As String

LogPath = ConfigurationManager.AppSettings("DebugLogLocation")
environment = ConfigurationManager.AppSettings("Environment")

If LogPath = "" Then LogPath = FilePath

LogPath = LogPath & environment & " Log - " & Format(Date.Today, "d MMM yyyy") & ".log"

If File.Exists(LogPath) = True OrElse CheckFilePath(LogPath) Then
Dim sr As StreamWriter = File.AppendText(LogPath)
sr.WriteLine(ErrorMessage)
sr.Close()
End If
End Sub

Private Function CheckFilePath(ByVal FilePath As String) As Boolean
Dim strChar As String
Try
If FilePath > "" Then
strChar = ""
If Not Directory.GetParent(FilePath).Exists Then
Do While Directory.GetParent(FilePath).Exists = False
strChar = Directory.GetParent(FilePath).ToString
Do While Not Directory.GetParent(strChar).Exists And strChar > ""
strChar = Directory.GetParent(strChar).ToString
Loop
Directory.CreateDirectory(strChar)
Loop
End If
End If
CheckFilePath = True
Catch Ex As Exception
CheckFilePath = False
End Try
End Function

End Class

Any idea how I could modify this so that it is threadsafe so that all the requests are written to the log in order?

I guess that instantiating a new instance of ErrorLog every time dBug is called is probably something that definitely needs to change...

Any pearls of wisdom or working examples would be most appreciated.

Cheers.

 

[chrissie1]

Try using log4net or nlog both designed for these cases.

Christiaan Baes
Belgium

My Blog
"In a system where you can define a factor as part of a third factor, you need another layer to check the main layer in case the second layer is not the base unit." - jrbarnett

 

[blondebier]

Thanks for the reply. I've had a go with NLog.

I have created a simple WebService to test this that goes something like this:

Imports NLog
Imports System.Web.Services
Imports System.Web.Services.Protocols
Imports System.ComponentModel

<System.Web.Services.WebService(Namespace:="

http://tempuri.org/")>

_
<System.Web.Services.WebServiceBinding(ConformsTo:=WsiProfiles.BasicProfile1_1)> _
<ToolboxItem(False)> _
Public Class test
Inherits System.Web.Services.WebService

Private Shared logger As Logger = LogManager.GetCurrentClassLogger()

<WebMethod()> _
Public Function TestXML(ByVal request As String) As String
Try
logger.Debug("XML Received : " & request)
Dim testMe As New XMLSchemaValidator
logger.Debug("Testing XML 1.")
Return testMe.ValidateXML(request)

Catch ex As Exception
logger.DebugException("Oh dear! ", ex)
Finally
logger.Debug("Testing XML 2")
End Try
End Function

End Class

What can I do so that I can reference the same instance of NLog in my other classes e.g. XMLSchemaValidator

Testing this as it is appears to just create one instance of logger and reuse it over and over again... so the problem I had re-occurs.

I think for this to work I would need it to create a new instance of "Logger" every time the WebMethod is called.

But I'm stumped as to how I do that...

 

[blondebier]

I guess I could just declare an instance of the Logger at the top of my WebMethod and pass the instanciated variable byRef to all classes and methods as required and then destroy it at the end of my WebMethod...?

Seems a bit much like hard work though. Declaring it like a "Global Protected for this instance" type variable would be much easier.

Is that possible?