void cn_InfoMessage(object sender, SqlInfoMessageEventArgs e)
{
TraceHelper.TraceEvent(System.Diagnostics.TraceEventType.Verbose, "SqlConnection.InfoMessage " + e.Message, "cn_InfoMessage");
}
internal SsbConversationGroupReceiver AcceptConversationGroup(TimeSpan timeout)
{
TimeoutHelper helper = new TimeoutHelper(timeout);
try
{
//create a transaction to own the conversation. Open the SqlConnection while
//the transaction is current, so all the work on the connection will be enlisted
//in the transaction. SqlTransaction doesn't work this way. It requires every command
//to be manually enlisted, yuck.
//As an alternative you could simply issue a new SqlCommand("begin transaction",cn).ExecuteNonQuery()
//to start a transaction.
// TODO (dbrowne) Consider whether to allow service-level code to commit this transaction, or, alternatively,
//commit the transaction after the last conversation message in this session is processed.
//If service-level code is allowed to commit the transaction then SsbConversationGroupReciver _must_
//retrieve only a single message in each batch. Else it could fetch 2 messages and risk the service-level
//commiting after the first message.
CommittableTransaction tx = new CommittableTransaction(TimeSpan.MaxValue);
Transaction currentTrans = Transaction.Current;
Transaction.Current = tx;
SqlConnection cn = SsbHelper.GetConnection(this.connstring);
cn.Open();
Transaction.Current = currentTrans;
tx.TransactionCompleted += new TransactionCompletedEventHandler(tx_TransactionCompleted);
//wait for a new message, but if that message is in a conversation group that another SsbChannelListener is waiting on
//then roll back the conversation group lock and get back in line. The waiting SsbChannelListener should pick it up.
string sql = String.Format(@"
retry:
save transaction swiper_no_swiping
declare @cg uniqueidentifier
declare @rc int
waitfor (get conversation group @cg from [{0}]), TIMEOUT @timeout
if @cg is null
begin
return --timeout
end
exec @rc = sp_getapplock @Resource=@cg, @LockMode='Exclusive', @LockTimeout = 0
if @rc = -1
begin
print 'skipping message for locked conversation_group'
rollback transaction swiper_no_swiping
goto retry
end
set @conversation_group_id = @cg
", this.serviceInfo.QueueName);
SqlCommand cmd = new SqlCommand(sql, cn);
cmd.CommandTimeout = 0;
cn.InfoMessage += new SqlInfoMessageEventHandler(cn_InfoMessage);
SqlParameter pTimeout = cmd.Parameters.Add("@timeout", SqlDbType.Int);
pTimeout.Value = TimeoutHelper.ToMilliseconds(timeout);
SqlParameter pConversationGroupId = cmd.Parameters.Add("@conversation_group_id", SqlDbType.UniqueIdentifier);
pConversationGroupId.Direction = ParameterDirection.Output;
//Run the command, but abort if the another thread runs Close or Abort
IAsyncResult result = cmd.BeginExecuteNonQuery();
int rc = WaitHandle.WaitAny(new WaitHandle[] { result.AsyncWaitHandle, cancelEvent });
if (rc == 1) //cancel event
{
cmd.Cancel();
TraceHelper.TraceEvent(System.Diagnostics.TraceEventType.Verbose, "Canceling Service Broker wait on SsbChannelListener shutdown", "AcceptConversationGroup");
cn.Close();
return(null);
}
if (rc != 0)
{
throw new InvalidOperationException("Unexpected state");
}
cmd.EndExecuteNonQuery(result);
if (pConversationGroupId.Value == null || pConversationGroupId.Value.GetType() != typeof(Guid))
{
throw new TimeoutException(String.Format("Timed out while waiting for Conversation Group"));
}
Guid conversationGroupId = (Guid)pConversationGroupId.Value;
TraceHelper.TraceEvent(System.Diagnostics.TraceEventType.Verbose, string.Format("Accepted conversation group {0}", conversationGroupId), "AcceptConversationGroup");
SsbConversationGroupReceiver cg = new SsbConversationGroupReceiver(cn, tx, conversationGroupId, this.serviceInfo, this);
return(cg);
}
catch (SqlException ex)
{
if (!helper.IsTimeRemaining)
{
throw new TimeoutException(String.Format("Timed out while waiting for Conversation Group. Timeout value was {0} seconds", timeout.TotalSeconds), ex);
}
else
{
throw new ProtocolException("An error occurred while waiting for a Conversation Group", ex);
}
}
}
void tx_TransactionCompleted(object sender, TransactionEventArgs e)
{
TraceHelper.TraceEvent(System.Diagnostics.TraceEventType.Verbose, string.Format("SsbChannelListener Transaction completed - {0}", e.Transaction.TransactionInformation.Status), "tx_TransactionCompleted");
}
internal SsbConversationGroupReceiver AcceptConversationGroup(Guid conversationGroupId, TimeSpan timeout)
{
TimeoutHelper helper = new TimeoutHelper(timeout);
TransactionOptions to = new TransactionOptions();
to.IsolationLevel = System.Transactions.IsolationLevel.ReadCommitted;
to.Timeout = TimeSpan.MaxValue;
CommittableTransaction tx = new CommittableTransaction(to);
Transaction currentTrans = Transaction.Current;
Transaction.Current = tx;
SqlConnection cn = SsbHelper.GetConnection(this.connstring);
cn.Open();
Transaction.Current = currentTrans;
//first lock the the Conversation Group. This will prevent other SsbConversationGroupReceivers
//from poaching the messages.
string sql = @"
declare @cg uniqueidentifier
declare @rc int
set @cg = @conversation_group_id
exec @rc = sp_getapplock @Resource=@cg, @LockMode='Exclusive'
if @rc not in (0,1)
begin
raiserror('Failed to lock conversation group. sp_getapplock failure code %d.',16,1,@rc);
end
";
SqlCommand cmd = new SqlCommand(sql, cn);
SqlParameter pConversationGroupId = cmd.Parameters.Add("@conversation_group_id", SqlDbType.UniqueIdentifier);
pConversationGroupId.Value = conversationGroupId;
cmd.CommandTimeout = helper.RemainingTimeInMillisecondsOrZero();
//Run the command, but abort if the another thread runs Close or Abort
IAsyncResult result = cmd.BeginExecuteNonQuery();
int rc = WaitHandle.WaitAny(new WaitHandle[] { result.AsyncWaitHandle, cancelEvent });
if (rc == 1) //cancel event
{
cmd.Cancel();
TraceHelper.TraceEvent(System.Diagnostics.TraceEventType.Verbose, "Canceling Service Broker wait on SsbChannelListener shutdown", "AcceptConversationGroup");
cn.Close();
return(null);
}
if (rc != 0)
{
throw new InvalidOperationException("Unexpected state");
}
cmd.EndExecuteNonQuery(result);
SsbConversationGroupReceiver cg = new SsbConversationGroupReceiver(cn, tx, conversationGroupId, this.serviceInfo, this);
cg.Open();
//now wait for a message on the conversation. Do it here because WCF expects the wait to be here instead of in a subsequent receive.
//And also there is a different timeout to accepting a channel and waiting for additional messages.
//But we need to pass in the cancelEvent to abort the listen, if this ChannelListener is closed or aborted
if (!cg.WaitForFirstMessage(helper.RemainingTime(), cancelEvent))
{
if (this.State != CommunicationState.Opened)//this ChannelListener was closed or aborted, so this is expected.
{
//for some reason the transaction tx is in an uncommitable state here. Not sure why.
//however no other work has occured on this connection, so we can just shut it down.
cn.Close();
return(null);
}
throw new TimeoutException(String.Format("Timed out while waiting for Conversation Group"));
}
return(cg);
}
