[Tarantool-patches] [PATCH v3 5/6] qsync: implement direct write of CONFIRM/ROLLBACK into a journal
Vladislav Shpilevoy
v.shpilevoy at tarantool.org
Mon Jul 27 23:41:17 MSK 2020
Thanks for the patch!
> diff --git a/src/box/txn_limbo.c b/src/box/txn_limbo.c
> index a74bfe244..d8cf6a6f6 100644
> --- a/src/box/txn_limbo.c
> +++ b/src/box/txn_limbo.c
> @@ -237,62 +240,73 @@ txn_limbo_wait_complete(struct txn_limbo *limbo, struct txn_limbo_entry *entry)
> return 0;
> }
>
> +/**
> + * A callback for synchronous write: txn_limbo_write fiber
> + * waiting to proceed once a record is written to WAL.
> + */
> +static void
> +txn_limbo_write_cb(struct journal_entry *entry)
> +{
> + assert(entry->complete_data != NULL);
> + fiber_wakeup(entry->complete_data);
> +}
> +
> +/**
> + * Write CONFIRM or ROLLBACK message to a journal directly
> + * without involving transaction engine because using txn
> + * engine is far from being cheap while we only need to
> + * write a small journal entry.
> + */
> static int
> -txn_limbo_write_confirm_rollback(struct txn_limbo *limbo, int64_t lsn,
> - bool is_confirm)
> +txn_limbo_write(uint32_t replica_id, int64_t lsn, int type)
> {
> + assert(replica_id != REPLICA_ID_NIL);
> + assert(type == IPROTO_CONFIRM || type == IPROTO_ROLLBACK);
> assert(lsn > 0);
>
> + /*
> + * When allocated statically some compilers (such as
> + * clang + asan) requires the journal_entry::rows to
> + * be last in a container structure. So it it simplier
> + * just to create a cummulative buffer.
> + */
> + char buf[sizeof(struct journal_entry) +
> + sizeof(struct xrow_header *)];
> +
> + struct synchro_body_bin body_bin;
> struct xrow_header row;
> - struct request request = {
> - .header = &row,
> - };
>
> - struct txn *txn = txn_begin();
> - if (txn == NULL)
> - return -1;
> + struct journal_entry *entry = (struct journal_entry *)buf;
> + entry->rows[0] = &row;
>
> - int res = 0;
> - if (is_confirm) {
> - res = xrow_encode_confirm(&row, &txn->region,
> - limbo->instance_id, lsn);
> - } else {
> - /*
> - * This LSN is the first to be rolled back, so
> - * the last "safe" lsn is lsn - 1.
> - */
> - res = xrow_encode_rollback(&row, &txn->region,
> - limbo->instance_id, lsn);
> + xrow_encode_synchro(&row, &body_bin, replica_id, lsn, type);
> +
> + journal_entry_create(entry, 1, xrow_approx_len(&row),
> + txn_limbo_write_cb, fiber());
> +
> + if (journal_write(entry) != 0) {
> + diag_set(ClientError, ER_WAL_IO);
> + diag_log();
> + return -1;
> }
> - if (res == -1)
> - goto rollback;
> - /*
> - * This is not really a transaction. It just uses txn API
> - * to put the data into WAL. And obviously it should not
> - * go to the limbo and block on the very same sync
> - * transaction which it tries to confirm now.
> - */
> - txn_set_flag(txn, TXN_FORCE_ASYNC);
>
> - if (txn_begin_stmt(txn, NULL) != 0)
> - goto rollback;
> - if (txn_commit_stmt(txn, &request) != 0)
> - goto rollback;
> + if (entry->res < 0) {
I suggest simply add '|| entry->res < 0' to the check above. To
make a single error handling point.
> + diag_set(ClientError, ER_WAL_IO);
> + diag_log();
> + return -1;
> + }
>
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