private static void NotifyResourceOfCommit(ITransactionalResource resource, long transaction, MultiCompletionSource completionSource)
{
resource.Commit(transaction)
.ContinueWith(
(result, state) =>
{
var completion = (MultiCompletionSource)state;
if (result.Exception != null)
{
completion.SetException(result.Exception);
}
else
{
completion.SetOneResult();
}
},
completionSource,
CancellationToken.None,
TaskContinuationOptions.ExecuteSynchronously,
TaskScheduler.Default);
}
private async Task <bool> Checkpoint(Dictionary <ITransactionalResource, long> resources, List <Transaction> transactions)
{
// Rather than continue processing forever, only process the number of transactions which were waiting at invocation time.
var total = this.checkpointRetryQueue.Count + checkpointQueue.Count;
// The maximum number of transactions checkpointed in each batch.
int batchSize = Math.Min(total, MaxCheckpointBatchSize);
long lsn = 0;
try
{
var processed = 0;
while (processed < total && (this.checkpointRetryQueue.Count > 0 || !checkpointQueue.IsEmpty))
{
resources.Clear();
transactions.Clear();
// Take a batch of transactions to checkpoint.
var currentBatchSize = 0;
while (currentBatchSize < batchSize)
{
currentBatchSize++;
Transaction tx;
// If some previous operation had failed, retry it before proceeding with new work.
if (this.checkpointRetryQueue.Count > 0)
{
tx = this.checkpointRetryQueue.Dequeue();
}
else if (!checkpointQueue.TryDequeue(out tx))
{
break;
}
foreach (var resource in tx.Info.WriteSet.Keys)
{
resources[resource] = tx.Info.TransactionId;
}
lsn = Math.Max(lsn, tx.LSN);
transactions.Add(tx);
}
processed += currentBatchSize;
// If the transaction involved writes, send a commit notification to each resource which performed
// a write and wait for acknowledgement.
if (resources.Count > 0)
{
// Send commit notifications to all of the resources involved.
var completion = new MultiCompletionSource(resources.Count);
foreach (var resource in resources)
{
NotifyResourceOfCommit(resource.Key, resource.Value, completion);
}
// Wait for the commit notifications to be acknowledged by the resources.
await completion.Task;
}
// Mark the transactions as checkpointed.
foreach (var tx in transactions)
{
lock (tx)
{
tx.State = TransactionState.Checkpointed;
tx.HighestActiveTransactionIdAtCheckpoint = activeTransactionsTracker.GetHighestActiveTransactionId();
}
}
// Allow the transaction log to be truncated.
this.checkpointedLSN = lsn;
}
}
catch (Exception e)
{
// Retry all failed checkpoint operations.
foreach (var tx in transactions)
{
this.checkpointRetryQueue.Enqueue(tx);
}
this.Logger.Error(0, "Failure during checkpoint", e);
throw;
}
return(total > 0);
}