How can I use sqlwrite with backgroundPool?

I am receiving real-time data and saving the data to a MS SQL Server database using sqlwrite with no problem. I want to run this on the backgroundPool to ensure the main thread remains responsive to user input. I have Parallel Computing Toolbox and a JDBC connection object that reads and writes to the MS SQL Server database with no issue.

However, when I create a parallel.pool.Constant object and pass it to parfeval, the connection object fails the check for a valid connection (~isopen(conn)) that is found in both sqlwrite (line 56) and fetch (line 69).

conn = database( ... );
bgConn = parallel.pool.Constant(conn);
f = parfeval(backgroundPool,@(c)isopen(c.Value),1,bgConn);
disp(['Bg Pool // ConnIsOpen: ' num2str(fetchOutputs(f))]);

returns

Bg Pool // ConnIsOpen: 0

If I try a function handle, I get a different error message.

fhConn = @()database( ... );
bgFhConn = parallel.pool.Constant(fhConn);
f = parfeval(backgroundPool,@(c)isopen(c.Value),1,bgFhConn);
disp(['Bg Pool // ConnIsOpen: ' num2str(fetchOutputs(f))]);

returns

One or more futures resulted in an error.

Caused by:

Error using parallel.pool.Constant/get.Value (line 188)

Unable to create parallel.pool.Constant on the workers.

Unable to resolve the name 'com.mathworks.jmi.ClassLoaderManager.getClassLoaderManager'.

How can I use parfeval to run sqlwrite? I see the same behaviour in both MATLAB 2024a and 2025a. Thanks for your help.

Answer 1

[Raymond Norris]

@Dave rather than creating the connection on the client side and passing it to each worker, take a look at createConnectionForPool - Initialize parallel pool using database connection - MATLAB. createConnectionForPool creates a connection for each worker in the pool.