From 149fc1f727ae493dffd8f75cd4f81da888972945 Mon Sep 17 00:00:00 2001
From: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Date: Tue, 28 May 2024 22:57:35 +0200
Subject: [PATCH] box: introduce box_localize_vclock
The function takes the burden of explaining why this hack about
setting local component in a remote vclock is needed. It also
creates a new vclock, not alters an existing one. This is to
signify that the vclock is no longer what was received from a
remote host.
Otherwise it is too easy to actually mistreat this mutant vlock as
a remote vclock. That btw did happen and is fixed in following
commits.
In scope of #10047
NO_TEST=refactoring
NO_CHANGELOG=refactoring
NO_DOC=refactoring
(cherry picked from commit b8463960135365d74128a04e559713a58f493731)
---
src/box/box.cc | 56 +++++++++++++++++++++++++++-----------------------
1 file changed, 30 insertions(+), 26 deletions(-)
diff --git a/src/box/box.cc b/src/box/box.cc
index 19fd7cee3d..67dd4d6c3a 100644
--- a/src/box/box.cc
+++ b/src/box/box.cc
@@ -3920,6 +3920,26 @@ box_process_fetch_snapshot(struct iostream *io,
coio_write_xrow(io, &row);
}
+/**
+ * Replica vclock is used in gc state and recovery initialization - need to
+ * replace the remote 0-th component with the own one. This doesn't break
+ * recovery: it finds the WAL with a vclock strictly less than replia clock in
+ * all components except the 0th one.
+ *
+ * Note, that it would be bad to set 0-th component to a smaller value (like
+ * zero) - it would unnecessarily require additional WALs, which may have
+ * already been deleted.
+ *
+ * Speaking of gc, remote instances' local vclock components are not used by
+ * consumers at all.
+ */
+static void
+box_localize_vclock(const struct vclock *remote, struct vclock *local)
+{
+ vclock_copy(local, remote);
+ vclock_reset(local, 0, vclock_get(&replicaset.vclock, 0));
+}
+
void
box_process_register(struct iostream *io, const struct xrow_header *header)
{
@@ -3965,10 +3985,10 @@ box_process_register(struct iostream *io, const struct xrow_header *header)
"wal_mode = 'none'");
}
- /* @sa box_process_subscribe(). */
- vclock_reset(&req.vclock, 0, vclock_get(&replicaset.vclock, 0));
+ struct vclock start_vclock;
+ box_localize_vclock(&req.vclock, &start_vclock);
struct gc_consumer *gc = gc_consumer_register(
- &req.vclock, "replica %s", tt_uuid_str(&req.instance_uuid));
+ &start_vclock, "replica %s", tt_uuid_str(&req.instance_uuid));
if (gc == NULL)
diag_raise();
auto gc_guard = make_scoped_guard([&] { gc_consumer_unregister(gc); });
@@ -3990,13 +4010,12 @@ box_process_register(struct iostream *io, const struct xrow_header *header)
/* Remember master's vclock after the last request */
struct vclock stop_vclock;
vclock_copy(&stop_vclock, &replicaset.vclock);
-
/*
- * Feed replica with WALs in range
- * (req.vclock, stop_vclock) so that it gets its
- * registration.
+ * Feed replica with WALs up to the REGISTER itself so that it gets own
+ * registration entry.
*/
- relay_final_join(replica, io, header->sync, &req.vclock, &stop_vclock);
+ relay_final_join(replica, io, header->sync, &start_vclock,
+ &stop_vclock);
say_info("final data sent.");
RegionGuard region_guard(&fiber()->gc);
@@ -4247,6 +4266,8 @@ box_process_subscribe(struct iostream *io, const struct xrow_header *header)
tnt_raise(ClientError, ER_UNSUPPORTED, "Replication",
"wal_mode = 'none'");
}
+ struct vclock start_vclock;
+ box_localize_vclock(&req.vclock, &start_vclock);
/*
* Send a response to SUBSCRIBE request, tell
* the replica how many rows we have in stock for it,
@@ -4297,23 +4318,6 @@ box_process_subscribe(struct iostream *io, const struct xrow_header *header)
coio_write_xrow(io, &row);
sent_raft_term = req.term;
}
- /*
- * Replica vclock is used in gc state and recovery
- * initialization, so we need to replace the remote 0-th
- * component with our own one. This doesn't break
- * recovery: it finds the WAL with a vclock strictly less
- * than replia clock in all components except the 0th one.
- * This leads to finding the correct WAL, if it exists,
- * since we do not need to recover local rows (the ones,
- * that contribute to the 0-th vclock component).
- * Note, that it would be bad to set 0-th vclock component
- * to a smaller value, since it would unnecessarily
- * require additional WALs, which may have already been
- * deleted.
- * Speaking of gc, remote instances' local vclock
- * components are not used by consumers at all.
- */
- vclock_reset(&req.vclock, 0, vclock_get(&replicaset.vclock, 0));
/*
* Process SUBSCRIBE request via replication relay
* Send current recovery vector clock as a marker
@@ -4326,7 +4330,7 @@ box_process_subscribe(struct iostream *io, const struct xrow_header *header)
* a stall in updates (in this case replica may hang
* indefinitely).
*/
- relay_subscribe(replica, io, header->sync, &req.vclock,
+ relay_subscribe(replica, io, header->sync, &start_vclock,
req.version_id, req.id_filter, sent_raft_term);
}
--
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