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Normally when a JE transaction is blocked on a lock request, it must wait until the requested lock becomes available before its thread-of-control can proceed. However, it is possible to configure a transaction handle such that it will report a deadlock rather than wait for the block to clear.
You do this on a transaction by transaction basis by specifying DB_TXN_NOWAIT to the DB_ENV->txn_begin() method.
For example:
/* Get the transaction */ DB_TXN *txn = NULL; ret = envp->txn_begin(envp, NULL, &txn, DB_TXN_NOWAIT); if (ret != 0) { envp->err(envp, ret, "txn_begin failed"); return (EXIT_FAILURE); } .... /* Deadlock detection and exception handling omitted for brevity. */