public async Task Initialize(long headLo, long headHi, long tailLo, long tailHi, SqlConnection conn)
{
if (linkState.Initialized)
{
return; //We ignore duplicate initialize messages.
}
LinkState initialized;
using (var initTransaction = conn.BeginTransaction())
{
initialized = linkState.Initialize(
InboxTable.Left(sourceKey, destinationKey), headLo, headHi,
InboxTable.Right(sourceKey, destinationKey), tailLo, tailHi);
await initialized.HeadSession.CreateConstraint(conn, initTransaction).ConfigureAwait(false);
await initialized.TailSession.CreateConstraint(conn, initTransaction).ConfigureAwait(false);
await linkStateTable.Update(sourceKey, initialized, conn, initTransaction).ConfigureAwait(false);
initTransaction.Commit();
}
UpdateCachedLinkState(initialized);
}
public async Task Uninstall(string sourceKey, SqlConnection conn, SqlTransaction trans)
{
var linkStateTable = new LinkStateTable(destinationKey);
await linkStateTable.Drop(conn, trans).ConfigureAwait(false);
await new InboxTable(InboxTable.Left(sourceKey, destinationKey)).Drop(conn, trans).ConfigureAwait(false);
await new InboxTable(InboxTable.Right(sourceKey, destinationKey)).Drop(conn, trans).ConfigureAwait(false);
}
public async Task <DeduplicationResult> Deduplicate(string messageId, long seq, SqlConnection conn, SqlTransaction trans)
{
var cachedLinkState = linkState;
if (cachedLinkState.IsDuplicate(seq))
{
return(DeduplicationResult.Duplicate);
}
if (cachedLinkState.IsFromNextEpoch(seq))
{
var freshLinkState = await linkStateTable.Get(sourceKey, conn, trans).ConfigureAwait(false);
UpdateCachedLinkState(freshLinkState);
cachedLinkState = linkState;
}
if (cachedLinkState.IsFromNextEpoch(seq))
{
throw new ProcessCurrentMessageLaterException("The message requires advancing epoch. Moving it to the back of the queue.");
}
if (cachedLinkState.IsDuplicate(seq))
{
return(DeduplicationResult.Duplicate);
}
var tableName = cachedLinkState.GetTableName(seq);
var table = new InboxTable(tableName);
try
{
await table.Insert(messageId, seq, conn, trans);
return(DeduplicationResult.OK);
}
catch (SqlException e)
{
if (e.Number == 547) //Constraint violation
{
var freshLinkState = await linkStateTable.Get(sourceKey, conn, trans).ConfigureAwait(false);
UpdateCachedLinkState(freshLinkState);
if (freshLinkState.IsDuplicate(seq))
{
return(DeduplicationResult.Duplicate);
}
throw new ProcessCurrentMessageLaterException("Link state is stale. Processing current message later.");
}
if (e.Number == 2627) //Unique index violation
{
return(DeduplicationResult.Duplicate);
}
throw;
}
}
public async Task <LinkState> Advance(long nextEpoch, long nextLo, long nextHi, SqlConnection conn)
{
//Let's actually check if our values are correct.
var queriedLinkState = await linkStateTable.Get(sourceKey, conn, null);
if (!queriedLinkState.Initialized)
{
throw new ProcessCurrentMessageLaterException($"Link state for {sourceKey} is not yet initialized. Cannot advance the epoch.");
}
var tableName = queriedLinkState.TailSession.Table;
var table = new InboxTable(tableName);
log.Debug($"Closing inbox table {tableName}.");
LinkState newLinkState;
using (var closeTransaction = conn.BeginTransaction())
{
//Ensure only one process can enter here
var lockedLinkState = await linkStateTable.Lock(sourceKey, conn, closeTransaction);
if (lockedLinkState.Epoch != queriedLinkState.Epoch)
{
throw new ProcessCurrentMessageLaterException($"Link state for {sourceKey} does not match previously read value. Cannot advance the epoch.");
}
if (nextEpoch < lockedLinkState.Epoch + 1)
{
//This is an old message that we already processed.
return(lockedLinkState);
}
if (nextEpoch > lockedLinkState.Epoch + 1)
{
throw new ProcessCurrentMessageLaterException($"The link state is at epoch {lockedLinkState.Epoch} and is not ready to transition to epoch {nextEpoch}.");
}
if (await table.HasHoles(queriedLinkState.TailSession, conn, closeTransaction).ConfigureAwait(false))
{
throw new ProcessCurrentMessageLaterException($"Inbox table {tableName} seems to have holes in the sequence. Cannot close yet.");
}
newLinkState = lockedLinkState.Advance(nextLo, nextHi);
await newLinkState.HeadSession.CreateConstraint(conn, closeTransaction);
//Here we have all holes plugged and no possibility of inserting new rows. We can truncate
log.Debug($"Truncating table {tableName}.");
await table.Truncate(conn, closeTransaction).ConfigureAwait(false);
await lockedLinkState.TailSession.DropConstraint(conn, closeTransaction).ConfigureAwait(false);
log.Debug($"Updating link state for {sourceKey} to {newLinkState}.");
await linkStateTable.Update(sourceKey, newLinkState, conn, closeTransaction).ConfigureAwait(false);
closeTransaction.Commit();
}
UpdateCachedLinkState(newLinkState);
return(newLinkState);
}