How to discover if a transaction is frequently aborting?

Question

I'm trying to debug a program that uses STM. The ThreadScope readings is pointing out a very high CPU activity as you can see here:

So I'm trying to find out if this is happening due to a transaction that frequently aborts. The first thing that I thought was using something like this to test:

atomically $ do
  someWork 
  ...
`orElse` do
  unsafeIOToSTM $ traceEventIO "transaction aborted!"
  retry

But I'm not sure if this is correct or if this is the best approach to debugging in an STM scenario. Any ideas?

Confluent

That would have been my approach as well. – Crosslink

What results did you get from this approach? – Phylys

There are no traces. If this approach is correct, no transaction is aborting. – Confluent

Answer 1

Use stm-stats package. It provides trackSTM that you should use instead of atomically, and dumpSTMStats :: IO () that will provide something like this:

STM transaction statistics (2011-10-09 12:28:37.188951 UTC):
Transaction     Commits    Retries      Ratio
_anonymous_           1          0       0.00
reader                1         23      23.00
writer               23          0       0.00

(Transaction names will be generated automatically, but there's helpers to set your own.)

Animated

Sorry for the long delay to respond. It seems that this package is not updated for a long time. I'll take a look how they check for retries. Thanks! – Confluent

I wouldn't be concerned about lack of updates: 1) Joachim, the maintainer, is well-known in the community; 2) the package is in Stackage LTS, which means it at least builds. – Animated

Just had some time to test stm-stats and it worked perfectly! The problem was indeed a transaction frequently aborting. Thank you! – Confluent