concurrency/lock problem?

[Matias Woloski]

I have the following code which is running in every Page_Load of my ASP.Net
app.
It basically will add rows to a table upto MAX_CACHED_ITEMS and then will
flush all the cached items to the database.

Do you foresee any concurrency problem? or any performance problem?

private object lockObject = new object();
private static DataTable myTable; //typed table
private const int MAX_CACHED_ITEMS = 50;

lock(lockObject)
{
if( myTable == null )
{
myTable = MyDal.CreateDataTable();
}
myTable.AddxxxxRow( param1, param2, param3 );
if( myTable.Rows.Count >= MAX_CACHED_ITEMS )
{
try
{
MyDal.MyTable.Update( myTable ); // update the db
MAX_CACHED_ITEMS rows
myTable.Rows.Clear();
}
catch( Exception ex )
{
//handle
}
}
}


Thanks,
Matias

 

[Willy Denoyette [MVP]]

I have the following code which is running in every Page_Load of my ASP.Net
app.
It basically will add rows to a table upto MAX_CACHED_ITEMS and then will
flush all the cached items to the database.

Do you foresee any concurrency problem? or any performance problem?

private object lockObject = new object();
private static DataTable myTable; //typed table
private const int MAX_CACHED_ITEMS = 50;

lock(lockObject)
{
if( myTable == null )
{
myTable = MyDal.CreateDataTable();
}
myTable.AddxxxxRow( param1, param2, param3 );
if( myTable.Rows.Count >= MAX_CACHED_ITEMS )
{
try
{
MyDal.MyTable.Update( myTable ); // update the db
MAX_CACHED_ITEMS rows
myTable.Rows.Clear();
}
catch( Exception ex )
{
//handle
}
}
}


Thanks,
Matias

Statics are the worse enemy of performance/scalability in web applications.
So why do you make your myTable static, make it an instance member and
remove the lock.

Willy.

 

[Jon Skeet [C# MVP]]

I have the following code which is running in every Page_Load of my ASP.Net
app.
It basically will add rows to a table upto MAX_CACHED_ITEMS and then will
flush all the cached items to the database.

Do you foresee any concurrency problem? or any performance problem?

Yes - your lock is effectively doing nothing, as you'll have a new
instance of the page for every request.

You need to lock on something shared.

 

[Matias Woloski]

sorry, I mistyped the code.

The lock object is static.

private static object lockObject = new object();

Now?

 

[Willy Denoyette [MVP]]

sorry, I mistyped the code.

The lock object is static.

private static object lockObject = new object();

Now?

The question is why do you share the table, I don't see any, but you might
have good reasons to do so, in that case there is nothing else you can do
than synchronize access to it.

Willy.

 

[Matias Woloski]

The question is why do you share the table, I don't see any, but you might
have good reasons to do so, in that case there is nothing else you can do
than synchronize access to it.

I could create an instance and save it to the cache.
Now, the difference between having static or cache is just that the cache
will manage expiration, right?

Btw, I need to have a global scoped table because I'm storing Page-View
records in this table, so I want to add rows to that table for any user that
enter in my app. When I reach MAXITEMS I will flush the table to the
database

That make sense?

Thanks,
Matias

 

[Willy Denoyette [MVP]]

I could create an instance and save it to the cache.
Now, the difference between having static or cache is just that the cache
will manage expiration, right?

Btw, I need to have a global scoped table because I'm storing Page-View
records in this table, so I want to add rows to that table for any user
that enter in my app. When I reach MAXITEMS I will flush the table to the
database

That make sense?

Thanks,
Matias

I would add the record to the cache after having updated the Database (note
that you can always use a private cache for the table data if you wan't to
update in batches). That way you reduce the time you are holding a lock to
the time it takes to update the cache.

Willy.