Issue writing to single file in Web service in .NET

Question

I have created a webservice in .net 2.0, C#. I need to log some information to a file whenever different methods are called by the web service clients.

The problem

Answer 1

Joel and charles. That was quick! :)

Joel: When you say "queue line" do you mean creating a separate thread that runs in a loop to keep checking the queue as well as write to a file when it is not locked?

Charles: I know about MSMQ and windows service combination, but like I said I have no choice other than writing to a file from within the web service :)

thanks pradeep_tp

Answer 2

The locking is probably failing because your webservice is being run by more than one worker process. You could protect the access with a named mutex, which is shared across processes, unlike the locks you get by using lock(someobject) {...}:

Mutex lock = new Mutex("mymutex", false);

lock.WaitOne();

// access file

lock.ReleaseMutex();

Answer 3

Maybe write a "queue line" of sorts for writing to the file, so when you try to write to the file it keeps checking to see if the file is locked, if it is - it keeps waiting, if it isn't locked - then write to it.

Answer 4

You don't say how your web service is hosted, so I'll assume it's in IIS. I don't think the file should be accessed by multiple processes unless your service runs in multiple application pools. Nevertheless, I guess you could get this error when multiple threads in one process are trying to write.

I think I'd go for the solution you suggest yourself, Pradeep, build a single object that does all the writing to the log file. Inside that object I'd have a Queue into which all data to be logged gets written. I'd have a separate thread reading from this queue and writing to the log file. In a thread-pooled hosting environment like IIS, it doesn't seem too nice to create another thread, but it's only one... Bear in mind that the in-memory queue will not survive IIS resets; you might lose some entries that are "in-flight" when the IIS process goes down.

Other alternatives certainly include using a separate process (such as a Service) to write to the file, but that has extra deployment overhead and IPC costs. If that doesn't work for you, go with the singleton.

Answer 5

It will wait until the mutex is released....