While working on a new model, our service tasks generated errors with backtraces which were too large to be stored in the various message related fields in the database. The engine crashed very ungracefully when that happened. Our fix was to change the table definitions so that instead of making message fields to have type `varchar(4000)`, they're defined as `text`.
I'm not sure if that is really the best fix. It might be better to have a limit and enforce it by the engine. In any case, running into a database error causes trouble that requires an engine restart, which should be avoided.
I tried to attach our changed `sql/create/postgres_engine_7.4.1-ee.sql` file for your consideration, but JIRA gave me the error message "No project could be found with id '10330'. Something on JIRA's end seems to be broken for file uploads. The only change that I made was the column type change as described above.