import ballerina/io;

public function main() returns error? {
    transaction {
        check update();
        check commit;
    }
}

transactional function update() returns error? {
    check updateDatabase();
    //  Registers a commit handler to be invoked when `commit` is executed.
    'transaction:onCommit(sendEmail);
    'transaction:onRollback(logError);
}

function updateDatabase() returns error? {
    io:println("Database updated");
}

isolated function sendEmail('transaction:Info info) {
    io:println("Email sent.");
}

isolated function logError('transaction:Info info,
                            error? cause, boolean willRetry) {
    io:println("Logged database update failure");
}

Commit/Rollback Handlers

Often code needs to get executed depending on whether a transaction committed. Testing the result of the commit within the transaction statement works, but inconvenient from a modularity perspective, particularly when you want to undo changes on rollback. This seems much worse in a distributed transaction, when transaction statement is in another program. Ballerina provides commit/rollback handlers which are functions that get run when decision whether to commit is known.

 
import ballerina/io;

public function main() returns error? {
    transaction {
        check update();
        check commit;
    }
}

transactional function update() returns error? {
    check updateDatabase();

    'transaction:onCommit(sendEmail);
    'transaction:onRollback(logError);
}

Registers a commit handler to be invoked when commit is executed.

 
function updateDatabase() returns error? {
    io:println("Database updated");
}

isolated function sendEmail('transaction:Info info) {
    io:println("Email sent.");
}

isolated function logError('transaction:Info info,
                            error? cause, boolean willRetry) {
    io:println("Logged database update failure");
}

bal run commit_rollback_handlers.bal
Database updated
Email sent.