public async Task GetAllTransactionsAndUpdateAccount(IBankAccount forBankAccount, CancellationToken cancellationToken)
{
// We are about to iterate through a process of:
//
// 1) Loop:
// a) Retrieve a page of data
// b) Kick off the integration that page data into our BankAccount (background thread)
// Until all pages have been retrieved.
//
// 2) Finally, wait for any remaining account work in step #b to be completed
//
// To optimize performance, the code below will overlap this work. That is, the intent is to
// allow for the I/O of the next socket call to be performed while we integrate the previous page into our
// Account - which is a CPU bound operation.
//
// Obviously, this requires a few things:
// a) That a single Account instance is thread safe in its work to merge. It's possible that we will have
// fast I/O and multiple pages may be merging concurrently.
// b) We need to recognize (and accept) that pages may be integrated into the Account in a different
// order than when they were received. In other words, transactions from page 3 may get processed before
// page 2.
//
int pageNumber = 1;
int remainingExpectedTransactions = 0;
List <Task> mergeIntoAccountTaskList = new List <Task>();
do
{
// Retrieve the next page
PageResponseDto pageResponse = await RestSinglePageProvider.GetPageOfTransactions(pageNumber, cancellationToken);
if (pageNumber == 1)
{
remainingExpectedTransactions = pageResponse.totalCount;
}
if (pageNumber != pageResponse.page)
{
throw new ApplicationException($"REST call to {RestSinglePageProvider} provided invalid page information. Expected pageNumber:{pageNumber} but received {pageResponse.page}.");
}
// Kick off a background task of merging the page transactions into the bank account
mergeIntoAccountTaskList.Add(Task.Factory.StartNew(() => forBankAccount.InsertBatchOfNewTransactions(pageResponse.transactions)));
// Update our transaction count and page number
remainingExpectedTransactions -= pageResponse.transactions.Count;
pageNumber += 1;
}while (remainingExpectedTransactions > 0);
// Wait until all of the pages have been merged
Task.WaitAll(mergeIntoAccountTaskList.ToArray(), cancellationToken);
}
