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  • com.datomic/datomic-pro "1.0.6242"
  • transactor process 0.9.6045


Given the following transaction function definition:

 [{:db/ident :demo-throw-fn
   :db/fn (d/function
           {:lang "clojure"
            :params '[db]
            :code '(throw (ex-info "demo" {:type (type #{:one})}))})}])

Execute the transaction function in two environments:

  1. A local environment
  2. An environment where the transactor runs in a separate process


Regardless of the environment, transaction function runtime errors are thrown.


  • In a local environment, execution of the demo function indeed throws an error - in line with expectations.
  • In an environment where the transactor runs in a separate process, the transactor times out.

Additional Notes

The hypothesis for the timeout is a second error occurs due to the
(type #{:one}) expression's result not being serializable. Unfortunately, the timeout error does not reveal what was likely known at some point during execution.

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Best answer

Hi David,

Thanks for the summary. I have noted that the error is not reported properly. This is a good candidate for a future enhancement.

Currently the recommendation (as you noted above) is to not return arbitrary things in the payload of the exception. Attempting to serialize arbitrary data will not be future functionality.

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