// Serialize a key and OutstandingTransactionsValue value to an encoded string
// The forceWrite parameter indicates whether to serialize to a string anyway even if there are no NACK RMs in the
// OutstandingTransactionsValue. This is needed sometimes (such as in recovery) to indicate a transaction has
// committed/aborted successfully and there are no remaining NACK RMs.
private string SerializeToString(string key, OutstandingTransactionsValue value, bool forceWrite = false)
{
// Only serialize if forceWrite is specified or if the list of NACK RMs is not empty
if (forceWrite || (value != null && value.nackRMList.Count > 0))
{
// Write the key to the string
System.Text.StringBuilder sb = new System.Text.StringBuilder(key);
if (value != null && value.nackRMList != null)
{
// Write the transaction type to the string
sb.Append("," + ((value.transactionType == OutstandingTransactionsValue.TransactionType.Commit) ? "0" : "1"));
// Write the list of NACK RMs to the string
foreach (string item in value.nackRMList)
{
sb.Append("," + item);
}
}
return(sb.ToString());
}
else
{
return(null);
}
}
// Serialize the key and CommittedTransactionValue value from an encoded string
private bool SerializeFromString(string s, out string key, out OutstandingTransactionsValue value)
{
key = null;
value = null;
string[] tokens = s.Split(','); // Split the string into tokens using a delimiter
if (tokens.Length == 0)
{
return(false);
}
key = tokens[0]; // The key is always the first token
value = new OutstandingTransactionsValue();
// The transaction type is the 2nd token (if it exists)
if (tokens.Length >= 2)
{
value.transactionType = (int.Parse(tokens[1]) == 0) ? OutstandingTransactionsValue.TransactionType.Commit : OutstandingTransactionsValue.TransactionType.Abort;
}
// The rest of the tokens (if they exist) is the list of RMs that have not acknowledge the commit/abort
value.nackRMList = tokens.Skip(2).ToList <string>();
return(true);
}
// Write a outstanding transaction entry to the file immediately
public void UpdateAndFlush(string transactionId, OutstandingTransactionsValue value)
{
// If the list of NACK RMs is empty, the transaction has committed/aborted successfully
// so remove it from the list of outstanding transactions
if (value == null || value.nackRMList == null || value.nackRMList.Count == 0)
{
transactionList.Remove(transactionId);
}
// Otherwise, add/update the outstanding transaction list.
else
{
transactionList[transactionId] = value;
}
// Append transaction information to file. If this is an existing transaction, it may
// cause the file to have multiple occurrences of the same transaction ID. We will take
// care of this in ReadFromFile() to make sure the last entry wins, this will avoid the need
// to rewrite the whole file every time an existing transaction is updated.
using (System.IO.StreamWriter sw = new StreamWriter(GetFilename(), true))
{
sw.WriteLine(SerializeToString(transactionId, value, true));
}
}
