Hello I have been playing with STM and want to log transactions to disk. Defining a logging function like:
log h act = unsafeIOToSTM $ hPrint h act works most the time. Aborts can be handled with: abort h = log h Abort >> retry atomic' h act = atomically (act `orElse` abort h) But is it possible to handle a commit? commit h = unsafeIOToSTM (hPrint h Commit >> hSync h) atomically2 h act = atomically ((act >> commit h) `orElse` abort h) This won't work because the transaction is validated and maybe aborted after the commit is logged to disk. Another alternative would be: atomically3 h act = atomically (act `orElse` abort h) >> atomically (commit h) But this does not work either. Given Trx1 and Trx2, the following may occur: 1) Trx1 commits <thread switch> 2) Trx2 commits (and depends on Trx1) 3) Trx2 commit is logged to disk <system crash> This means that the log would be inconsistent. Is there a way to implement the commit that works? - Einar Karttunen _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
