IBM MQ transactions and .net - ibm-mq

Question

I have used .net C# (IBM MQ version 9.1.5) to pull messages from the queue. So I have no issues connecting to the queue and getting messages.
I have read that there is the concept of transactions Distributed Transactions.
I tried the following:
var getMessageOptions = new MQGetMessageOptions();
getMessageOptions = new MQGetMessageOptions();
getMessageOptions.Options += MQC.MQGMO_WAIT + MQC.MQGMO_SYNCPOINT;
getMessageOptions.WaitInterval = 20000; // 20 seconds wait
Transaction oldAmbient = Transaction.Current;
using (var tx = new CommittableTransaction())
{
try
{
int i = queue.CurrentDepth;
Log.Information($"Current queue depth is {i} message(s)");
var message = new MQMessage();
queue.Get(message, getMessageOptions);
string messageStr = message.ReadString(message.DataLength);
Log.Information(messageStr);
tx.Commit();
}
catch (MQException e) when (e.Reason == 2033)
{
// Report exceptions other than "no messages in the queue"
Log.Information("No messages in the queue");
tx.Rollback();
}
catch (Exception ex)
{
Log.Error($"Exception when trying to capture a message from the queue: {ex.Message}");
tx.Rollback();
}
I am getting an error code of 2035.
Looking at the documents on Recovering Transactions, where does the "SYSTEM.DOTNET.XARECOVERY.QUEUE" live, is it on the queuemanger?
Do I need to get permissions enabled on this?
Also I see that Microsoft Distributed Transaction Manager is mentioned, is this something that we need to have running on the local host in order for distributed transactions to work?

Answer 1

If MQ Distributed transactions feature is being used then the user running the application should have the authority to "SYSTEM.DOTNET.XARECOVERY.QUEUE".If a transaction is incomplete "SYSTEM.DOTNET.XARECOVERY.QUEUE" queue holds the information of incomplete transaction as message in that queue,which later can be used to resolve the transaction.
Based on your scenario which you had put in comments i.e "we want to just save the message to a file. My thinking is if there is a problem with that, I could roll back the transaction." .If MQ is the only resource manager then you don't have to use Distributed transactions. Getting a message under syncpoint can also be used instead of Distributed Transactions. Distributed Transactions will be useful if more than one resource manager is being used.
To get a message under syncpoint following sample code can be used by updating hostname,channel,port,queue and queue manager name:
var getMessageOptions = new MQGetMessageOptions();
getMessageOptions = new MQGetMessageOptions();
getMessageOptions.Options += MQC.MQGMO_WAIT + MQC.MQGMO_SYNCPOINT;
getMessageOptions.WaitInterval = 20000; // 20 seconds wait
Hashtable props = new Hashtable();
props.Add(MQC.HOST_NAME_PROPERTY, "localhost");
props.Add(MQC.CHANNEL_PROPERTY, "DOTNET.SVRCONN");
props.Add(MQC.PORT_PROPERTY, 3636);
MQQueueManager qm = new MQQueueManager("QM", props);
MQQueue queue = qm.AccessQueue("Q1", MQC.MQOO_INPUT_AS_Q_DEF);
try
{
var message = new MQMessage();
queue.Get(message, getMessageOptions);
//to commit the message
qm.Commit();
string messageStr = message.ReadString(message.DataLength);
}
catch (MQException e) when (e.Reason == 2033)
{
// Report exceptions other than "no messages in the queue"
Log.Information("No messages in the queue");
}
catch (Exception ex)
{
Log.Error($"Exception when trying to capture a message from the queue:
}