Too many connections error on frmNewFormDaily2

[smachua]

@maxwellfundi and @Patowhiz this problem has been reported from Malawi DCCMS when about 10 users open the form simultaneously. Could there be connections that are multiplying or not closing. Less that 10 connections may be too few to cause a problem. What is your thinking?

[isedwards]

The default number of connections that MySQL allows is 151.

It's likely that there are places in the Climsoft code that are opening additional connections each time a window is opened, and we never close these connections, so eventually we reach the limit.

If approximately 10 users are using the software, and the software inadvertently opens over 10 connections for each user, then we'll soon reach the default limit.

[isedwards]

I've had a quick look at the code for user controls (all files matching: ucr*.vb)

ucrDirectionSpeedFlag.vb and ucrValueFlagPeriod.vb both appear to open a connection to the database and then not close the connection.

This will result in an extra connection remaining open each time one of these user controls is created in a form.

[isedwards]

@smachua - should we prioritise fixing this quickly and make an update installer that we can share with users next week?

The other pull requests that we have open at the moment (#528, #534 and #537) are more substantial changes that should have more time for testing before they are released, so I suggest we make a 4.1.4 release that just contains this bug fix.

[Patowhiz]

The current commit opens the connection once. We just need to close it when the user closes the application. We also need to have the other places opening connections to use the clsDataConnection class

[smachua]

@isedwards and @Patowhiz I identified the affected connections and fixed the problem. I will make the Pull Request by tomorrow.

[Patowhiz]

@smachua did you make the changes. I suggest we rely on the current clsDataConnection class for connecting to the database. We also have a clsDataCall class which is acting as our DAO (Data Access Object) layer. You could also use it to get a filled data table, and to do CRUD operations. We have designed it to counter possible SQL injections.

[isedwards]

Samuel has fixed the immediate problems in #546. I think it is sensible that the initial fix is done in this way with no complications for people who need the main bug fix straight away.

I also agree with updating everything to work with clsDataCall going forward, there are a lot of positives to this approach.

[smachua]

@Patowhiz and @isedwards I will look at clsDataCall and see how I can adapt it.

[Patowhiz]

Okay, I'll be on standby. There is also lots of new additions to it in the dev branch. I think you will get the changes after the merging.

[Patowhiz]

@isedwards @smachua with time we could implement the clsDataConnection class to a data connection pool, it will help eliminate the problem of many new connections created against the database. Data Connection Pools enable reusing of existing data connections by different users.