Is it possible to reasonably workaround an antivirus scanning the working directory?

Question

My Win32 application performs numerous disk operations in a designated temporary folder while functioning, and seriously redesigning it is out of the question.

Some clients have antivirus software that scans the same temporary directory (it simply scans everything). We tried to talk them into disabling it - it doesn't work, so it's out of the question either.

Every once in a while (something like once for every one thousand file operations) my application tries to perform an operation on a file which is at that very time opened by the antivirus and is therefore locked by the operating system. A sharing violation occurs and causes an error in my application. This happens about once in three minutes on average.

The temporary folder can contain up to 100k files in most typical scenarios, so I don't like the idea of having them open at all times because this could cause running out of resources on some edge conditions.

Is there some reasonable strategy for my application to react to situations when a needed file is locked? Maybe something like this?

for( int i = 0; i < ReasonableNumber; i++ ) {
    try {
        performOperation(); // do useful stuff here
        break;
    } catch( ... ) {
        if( i == ReasonableNumber - 1 ) {
            throw; //not to hide errors if unlock never happens
        }
    }
    Sleep( ReasonableInterval );
 }

Is this a viable strategy? If so, how many times and how often should my application retry? What are better ideas if any?

Answer 1

A virusscanner that locks files while it's scanning them is quite bad. Clients who have virusscanners this bad need to have their brains replaced... ;-)

Okay, enough ranting. If a file is locked by some other process then you can use a "try again" strategy like you suggest. OTOH, do you really need to close and then re-open those files? Can't you keep them open until your process is done? One tip: Add a delay (sleep) when you try to re-open the file again. About 100 ms should be enough. If the virusscanner keeps the file open that long then it's a real bad scanner. Clients with scanners that bad deserve the exception message that they'll see. Typically, try up to three times... -> Open, on failure try again, on second failure try again, on third failure just crash.

Remember to crash in a user-friendly way.