[tarantool-patches] [PATCH v2 1/5] Do not promote wal vclock for failed writes
Георгий Кириченко
georgy at tarantool.org
Tue Jan 29 13:22:21 MSK 2019
On Monday, January 28, 2019 2:20:18 PM MSK Vladimir Davydov wrote:
> On Tue, Jan 22, 2019 at 01:31:09PM +0300, Georgy Kirichenko wrote:
> > Increase replica lsn only if row was successfully written to disk. This
> > prevents wal from lsn gaps in case of IO errors and enforces wal
> > consistency.
> >
> > Needs for #980
> > ---
> >
> > src/box/wal.c | 19 ++++++---
> > test/xlog/errinj.result | 1 -
> > test/xlog/panic_on_lsn_gap.result | 65 +++++++++++++++----------------
> > 3 files changed, 45 insertions(+), 40 deletions(-)
> >
> > diff --git a/src/box/wal.c b/src/box/wal.c
> > index 3b50d3629..a55b544aa 100644
> > --- a/src/box/wal.c
> > +++ b/src/box/wal.c
> > @@ -901,16 +901,16 @@ wal_writer_begin_rollback(struct wal_writer *writer)
> >
> > }
> >
> > static void
> >
> > -wal_assign_lsn(struct wal_writer *writer, struct xrow_header **row,
> > +wal_assign_lsn(struct vclock *vclock, struct xrow_header **row,
> >
> > struct xrow_header **end)
> >
> > {
> >
> > /** Assign LSN to all local rows. */
> > for ( ; row < end; row++) {
> >
> > if ((*row)->replica_id == 0) {
> >
> > - (*row)->lsn = vclock_inc(&writer->vclock, instance_id);
> > + (*row)->lsn = vclock_inc(vclock, instance_id);
> >
> > (*row)->replica_id = instance_id;
> >
> > } else {
> >
> > - vclock_follow_xrow(&writer->vclock, *row);
> > + vclock_follow_xrow(vclock, *row);
> >
> > }
> >
> > }
> >
> > }
> >
> > @@ -922,6 +922,11 @@ wal_write_to_disk(struct cmsg *msg)
> >
> > struct wal_msg *wal_msg = (struct wal_msg *) msg;
> > struct error *error;
> >
> > + /* Local vclock copy. */
> > + struct vclock vclock;
> > + vclock_create(&vclock);
> > + vclock_copy(&vclock, &writer->vclock);
> > +
> >
> > struct errinj *inj = errinj(ERRINJ_WAL_DELAY, ERRINJ_BOOL);
> > while (inj != NULL && inj->bparam)
> >
> > usleep(10);
> >
> > @@ -974,14 +979,15 @@ wal_write_to_disk(struct cmsg *msg)
> >
> > struct journal_entry *entry;
> > struct stailq_entry *last_committed = NULL;
> > stailq_foreach_entry(entry, &wal_msg->commit, fifo) {
> >
> > - wal_assign_lsn(writer, entry->rows, entry->rows + entry-
>n_rows);
> > - entry->res = vclock_sum(&writer->vclock);
> > + wal_assign_lsn(&vclock, entry->rows, entry->rows + entry-
>n_rows);
> > + entry->res = vclock_sum(&vclock);
> >
> > rc = xlog_write_entry(l, entry);
> > if (rc < 0)
> >
> > goto done;
> >
> > if (rc > 0) {
> >
> > writer->checkpoint_wal_size += rc;
> > last_committed = &entry->fifo;
> >
> > + vclock_copy(&writer->vclock, &vclock);
>
> I don't like that you copy a vclock after applying each entry.
> Currently, it should be pretty cheap, but in future, when we make
> vclock store any number of ids, this might get pretty heavy.
> Can we minimize the number of memcpys somehow, ideally do it only
> on the rollback path?
In that case we should preserve vclock for rollback but it can be done only
with vclock_copy to. vclock_copy is used only for whole batch with all
entries.
When we introduce unlimited vclock we should introduce vclock_diff also and
then use them.
>
> > }
> > /* rc == 0: the write is buffered in xlog_tx */
> >
> > }
> >
> > @@ -991,6 +997,7 @@ wal_write_to_disk(struct cmsg *msg)
> >
> > writer->checkpoint_wal_size += rc;
> > last_committed = stailq_last(&wal_msg->commit);
> >
> > + vclock_copy(&writer->vclock, &vclock);
> >
> > /*
> >
> > * Notify TX if the checkpoint threshold has been exceeded.
> >
> > @@ -1185,7 +1192,7 @@ wal_write_in_wal_mode_none(struct journal *journal,
> >
> > struct journal_entry *entry)
> >
> > {
> >
> > struct wal_writer *writer = (struct wal_writer *) journal;
> >
> > - wal_assign_lsn(writer, entry->rows, entry->rows + entry->n_rows);
> > + wal_assign_lsn(&writer->vclock, entry->rows, entry->rows +
> > entry->n_rows);>
> > int64_t old_lsn = vclock_get(&replicaset.vclock, instance_id);
> > int64_t new_lsn = vclock_get(&writer->vclock, instance_id);
> > if (new_lsn > old_lsn) {
> >
> > diff --git a/test/xlog/errinj.result b/test/xlog/errinj.result
> > index 390404b47..7f15bef35 100644
> > --- a/test/xlog/errinj.result
> > +++ b/test/xlog/errinj.result
> > @@ -43,7 +43,6 @@ require('fio').glob(name .. "/*.xlog")
> >
> > ---
> > - - xlog/00000000000000000000.xlog
> >
> > - xlog/00000000000000000001.xlog
> >
> > - - xlog/00000000000000000002.xlog
> >
> > ...
> > test_run:cmd('restart server default with cleanup=1')
> > -- gh-881 iproto request with wal IO error
> >
> > diff --git a/test/xlog/panic_on_lsn_gap.result
> > b/test/xlog/panic_on_lsn_gap.result index 4dd1291f8..8054baab4 100644
> > --- a/test/xlog/panic_on_lsn_gap.result
> > +++ b/test/xlog/panic_on_lsn_gap.result
> > @@ -105,7 +105,7 @@ test_run:cmd("restart server panic")
> >
> > --
> > box.info.vclock
> > ---
> >
> > -- {1: 11}
> > +- {1: 1}
>
> After this patch the comments contradict the expected result of this
> test. Please fix.
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