I have setup a public queue that deliveries EDI documents to partner.
When this queue fails due to any I like to get notified
I have setup tn.task.notifyFailure = true
as per TN users guide, if the queue fails TN will publish wm.tn.rec.taskfailure document
I have written the trigger service, but TN does not published tackfailure doc. I dont see any errors in the logs
please provide some guidelines

Try the following

1. The trigger you are using to listen for wm.tn.rec.taskfailure is having the correct fully qualified document name.
2. Ensure the IS copy and the Broker copy of wm.tn.rec.taskfailure document are in sync.
3. Check out the corresponding trigger queue in the broker for the wm.tn.rec.taskfailure document, the last retrieved filed in the broker trigger page might help you get a better understanding of the problem.
4. Temporarily increase the logging level of the server to atleast 6 and then try recreating the issue.