[Tarantool-patches] [PATCH 4/5] [tosquash] replication: rework how local transactions wait sync
Vladislav Shpilevoy
v.shpilevoy at tarantool.org
Fri Jul 3 02:40:29 MSK 2020
There was a bug about how async transactions were blocked by a
not empty limbo. This was about fully local transactions. The
problem is that they don't have LSN in the needed vclock
component - it is always 0. It means, that their limbo entry
can't get a valid LSN by any means. Even a copy of the previous
sync transaction's LSN won't work, because the latter may by
still not written to WAL.
This patch makes async transactions always have lsn -1 in their
limbo entry. Because anyway it does not matter. It is not needed
to collect ACKs, nor to propagate limbo's vclock.
Now even a fully local transaction can be blocked by a pending
sync transaction.
Note, this does not cover the case, when the transaction is not
fully local, and its last row is local.
---
src/box/txn.c | 18 ++--
src/box/txn_limbo.c | 60 +++++++------
test/replication/qsync_basic.result | 120 ++++++++++++++++++++++++++
test/replication/qsync_basic.test.lua | 45 ++++++++++
4 files changed, 208 insertions(+), 35 deletions(-)
diff --git a/src/box/txn.c b/src/box/txn.c
index 6c333cbed..fe0591197 100644
--- a/src/box/txn.c
+++ b/src/box/txn.c
@@ -688,15 +688,15 @@ txn_commit_async(struct txn *txn)
/* See txn_commit(). */
uint32_t origin_id = req->rows[0]->replica_id;
- int64_t lsn = req->rows[txn->n_applier_rows - 1]->lsn;
limbo_entry = txn_limbo_append(&txn_limbo, origin_id, txn);
if (limbo_entry == NULL) {
txn_rollback(txn);
return -1;
}
- assert(lsn > 0);
- txn_limbo_assign_lsn(&txn_limbo, limbo_entry, lsn);
-
+ if (txn_has_flag(txn, TXN_WAIT_ACK)) {
+ int64_t lsn = req->rows[txn->n_applier_rows - 1]->lsn;
+ txn_limbo_assign_lsn(&txn_limbo, limbo_entry, lsn);
+ }
/*
* Set a trigger to abort waiting for confirm on
* WAL write failure.
@@ -779,10 +779,12 @@ txn_commit(struct txn *txn)
return -1;
}
if (is_sync) {
- int64_t lsn = req->rows[req->n_rows - 1]->lsn;
- txn_limbo_assign_lsn(&txn_limbo, limbo_entry, lsn);
- /* Local WAL write is a first 'ACK'. */
- txn_limbo_ack(&txn_limbo, txn_limbo.instance_id, lsn);
+ if (txn_has_flag(txn, TXN_WAIT_ACK)) {
+ int64_t lsn = req->rows[req->n_rows - 1]->lsn;
+ txn_limbo_assign_lsn(&txn_limbo, limbo_entry, lsn);
+ /* Local WAL write is a first 'ACK'. */
+ txn_limbo_ack(&txn_limbo, txn_limbo.instance_id, lsn);
+ }
if (txn_limbo_wait_complete(&txn_limbo, limbo_entry) < 0) {
txn_free(txn);
return -1;
diff --git a/src/box/txn_limbo.c b/src/box/txn_limbo.c
index 387cfd337..44a0c7273 100644
--- a/src/box/txn_limbo.c
+++ b/src/box/txn_limbo.c
@@ -120,6 +120,7 @@ txn_limbo_assign_lsn(struct txn_limbo *limbo, struct txn_limbo_entry *entry,
assert(limbo->instance_id != REPLICA_ID_NIL);
assert(entry->lsn == -1);
assert(lsn > 0);
+ assert(txn_has_flag(entry->txn, TXN_WAIT_ACK));
(void) limbo;
entry->lsn = lsn;
}
@@ -129,6 +130,12 @@ txn_limbo_check_complete(struct txn_limbo *limbo, struct txn_limbo_entry *entry)
{
if (txn_limbo_entry_is_complete(entry))
return true;
+ /*
+ * Async transaction can't complete itself. It is always
+ * completed by a previous sync transaction.
+ */
+ if (!txn_has_flag(entry->txn, TXN_WAIT_ACK))
+ return false;
struct vclock_iterator iter;
vclock_iterator_init(&iter, &limbo->vclock);
int ack_count = 0;
@@ -142,14 +149,13 @@ txn_limbo_check_complete(struct txn_limbo *limbo, struct txn_limbo_entry *entry)
}
static int
-txn_limbo_write_rollback(struct txn_limbo *limbo,
- struct txn_limbo_entry *entry);
+txn_limbo_write_rollback(struct txn_limbo *limbo, int64_t lsn);
int
txn_limbo_wait_complete(struct txn_limbo *limbo, struct txn_limbo_entry *entry)
{
struct txn *txn = entry->txn;
- assert(entry->lsn > 0);
+ assert(entry->lsn > 0 || !txn_has_flag(entry->txn, TXN_WAIT_ACK));
assert(!txn_has_flag(txn, TXN_IS_DONE));
assert(txn_has_flag(txn, TXN_WAIT_SYNC));
if (txn_limbo_check_complete(limbo, entry))
@@ -176,7 +182,7 @@ txn_limbo_wait_complete(struct txn_limbo *limbo, struct txn_limbo_entry *entry)
goto complete;
}
- txn_limbo_write_rollback(limbo, entry);
+ txn_limbo_write_rollback(limbo, entry->lsn);
struct txn_limbo_entry *e, *tmp;
rlist_foreach_entry_safe_reverse(e, &limbo->queue,
in_queue, tmp) {
@@ -210,10 +216,11 @@ complete:
}
static int
-txn_limbo_write_confirm_rollback(struct txn_limbo *limbo,
- struct txn_limbo_entry *entry,
+txn_limbo_write_confirm_rollback(struct txn_limbo *limbo, int64_t lsn,
bool is_confirm)
{
+ assert(lsn > 0);
+
struct xrow_header row;
struct request request = {
.header = &row,
@@ -221,14 +228,13 @@ txn_limbo_write_confirm_rollback(struct txn_limbo *limbo,
int res = 0;
if (is_confirm) {
- res = xrow_encode_confirm(&row, limbo->instance_id, entry->lsn);
+ res = xrow_encode_confirm(&row, limbo->instance_id, lsn);
} else {
/*
* This entry is the first to be rolled back, so
- * the last "safe" lsn is entry->lsn - 1.
+ * the last "safe" lsn is lsn - 1.
*/
- res = xrow_encode_rollback(&row, limbo->instance_id,
- entry->lsn - 1);
+ res = xrow_encode_rollback(&row, limbo->instance_id, lsn - 1);
}
if (res == -1)
return -1;
@@ -260,10 +266,9 @@ rollback:
* transactions waiting for confirmation may be finished.
*/
static int
-txn_limbo_write_confirm(struct txn_limbo *limbo,
- struct txn_limbo_entry *entry)
+txn_limbo_write_confirm(struct txn_limbo *limbo, int64_t lsn)
{
- return txn_limbo_write_confirm_rollback(limbo, entry, true);
+ return txn_limbo_write_confirm_rollback(limbo, lsn, true);
}
void
@@ -300,14 +305,13 @@ txn_limbo_read_confirm(struct txn_limbo *limbo, int64_t lsn)
/**
* Write a rollback message to WAL. After it's written
- * all the tarnsactions following the current one and waiting
+ * all the transactions following the current one and waiting
* for confirmation must be rolled back.
*/
static int
-txn_limbo_write_rollback(struct txn_limbo *limbo,
- struct txn_limbo_entry *entry)
+txn_limbo_write_rollback(struct txn_limbo *limbo, int64_t lsn)
{
- return txn_limbo_write_confirm_rollback(limbo, entry, false);
+ return txn_limbo_write_confirm_rollback(limbo, lsn, false);
}
void
@@ -316,7 +320,7 @@ txn_limbo_read_rollback(struct txn_limbo *limbo, int64_t lsn)
assert(limbo->instance_id != REPLICA_ID_NIL);
struct txn_limbo_entry *e, *tmp;
rlist_foreach_entry_safe_reverse(e, &limbo->queue, in_queue, tmp) {
- if (e->lsn <= lsn)
+ if (e->lsn <= lsn && txn_has_flag(e->txn, TXN_WAIT_ACK))
break;
e->is_rollback = true;
txn_limbo_pop(limbo, e);
@@ -350,31 +354,33 @@ txn_limbo_ack(struct txn_limbo *limbo, uint32_t replica_id, int64_t lsn)
int64_t prev_lsn = vclock_get(&limbo->vclock, replica_id);
vclock_follow(&limbo->vclock, replica_id, lsn);
struct txn_limbo_entry *e, *last_quorum = NULL;
+ int64_t confirm_lsn = -1;
rlist_foreach_entry(e, &limbo->queue, in_queue) {
+ assert(e->ack_count <= VCLOCK_MAX);
if (e->lsn > lsn)
break;
- if (e->lsn <= prev_lsn)
- continue;
- assert(e->ack_count <= VCLOCK_MAX);
/*
* Sync transactions need to collect acks. Async
* transactions are automatically committed right
* after all the previous sync transactions are.
*/
- if (txn_has_flag(e->txn, TXN_WAIT_ACK)) {
- if (++e->ack_count < replication_synchro_quorum)
- continue;
- } else {
- assert(txn_has_flag(e->txn, TXN_WAIT_SYNC));
+ if (!txn_has_flag(e->txn, TXN_WAIT_ACK)) {
+ assert(e->lsn == -1);
if (last_quorum == NULL)
continue;
+ } else if (e->lsn <= prev_lsn) {
+ continue;
+ } else if (++e->ack_count < replication_synchro_quorum) {
+ continue;
+ } else {
+ confirm_lsn = e->lsn;
}
e->is_commit = true;
last_quorum = e;
}
if (last_quorum == NULL)
return;
- if (txn_limbo_write_confirm(limbo, last_quorum) != 0) {
+ if (txn_limbo_write_confirm(limbo, confirm_lsn) != 0) {
// TODO: what to do here?.
// We already failed writing the CONFIRM
// message. What are the chances we'll be
diff --git a/test/replication/qsync_basic.result b/test/replication/qsync_basic.result
index 32deb2ac3..339fc0e33 100644
--- a/test/replication/qsync_basic.result
+++ b/test/replication/qsync_basic.result
@@ -299,6 +299,126 @@ box.space.sync:select{6}
| - []
| ...
+--
+-- Fully local async transaction also waits for existing sync txn.
+--
+test_run:switch('default')
+ | ---
+ | - true
+ | ...
+box.cfg{replication_synchro_timeout = 1000, replication_synchro_quorum = 2}
+ | ---
+ | ...
+_ = box.schema.create_space('locallocal', {is_local = true})
+ | ---
+ | ...
+_ = _:create_index('pk')
+ | ---
+ | ...
+-- Propagate local vclock to some insane value to ensure it won't
+-- affect anything.
+box.begin() for i = 1, 2000 do box.space.locallocal:replace{1} end box.commit()
+ | ---
+ | ...
+do \
+ f1 = fiber.create(box.space.sync.replace, box.space.sync, {8}) \
+ f2 = fiber.create(box.space.locallocal.replace, box.space.locallocal, {8}) \
+ box.space.test:replace{8} \
+end
+ | ---
+ | ...
+f1:status()
+ | ---
+ | - dead
+ | ...
+f2:status()
+ | ---
+ | - dead
+ | ...
+box.space.sync:select{8}
+ | ---
+ | - - [8]
+ | ...
+box.space.locallocal:select{8}
+ | ---
+ | - - [8]
+ | ...
+box.space.test:select{8}
+ | ---
+ | - - [8]
+ | ...
+
+test_run:switch('replica')
+ | ---
+ | - true
+ | ...
+box.space.sync:select{8}
+ | ---
+ | - - [8]
+ | ...
+box.space.locallocal:select{8}
+ | ---
+ | - []
+ | ...
+box.space.test:select{8}
+ | ---
+ | - - [8]
+ | ...
+
+-- Ensure sync rollback will affect all pending fully local async
+-- transactions too.
+test_run:switch('default')
+ | ---
+ | - true
+ | ...
+box.cfg{replication_synchro_timeout = 0.001, replication_synchro_quorum = 3}
+ | ---
+ | ...
+do \
+ f1 = fiber.create(box.space.sync.replace, box.space.sync, {9}) \
+ f2 = fiber.create(box.space.locallocal.replace, box.space.locallocal, {9}) \
+ box.space.test:replace{9} \
+end
+ | ---
+ | - error: A rollback for a synchronous transaction is received
+ | ...
+f1:status()
+ | ---
+ | - dead
+ | ...
+f2:status()
+ | ---
+ | - dead
+ | ...
+box.space.sync:select{9}
+ | ---
+ | - []
+ | ...
+box.space.locallocal:select{9}
+ | ---
+ | - []
+ | ...
+box.space.test:select{9}
+ | ---
+ | - []
+ | ...
+test_run:switch('replica')
+ | ---
+ | - true
+ | ...
+box.space.sync:select{9}
+ | ---
+ | - []
+ | ...
+box.space.locallocal:select{9}
+ | ---
+ | - []
+ | ...
+box.space.test:select{9}
+ | ---
+ | - []
+ | ...
+
--
-- gh-5123: quorum 1 still should write CONFIRM.
--
diff --git a/test/replication/qsync_basic.test.lua b/test/replication/qsync_basic.test.lua
index 361f22bc3..6e40131bf 100644
--- a/test/replication/qsync_basic.test.lua
+++ b/test/replication/qsync_basic.test.lua
@@ -118,6 +118,51 @@ test_run:switch('replica')
box.space.test:select{6}
box.space.sync:select{6}
+--
+-- Fully local async transaction also waits for existing sync txn.
+--
+test_run:switch('default')
+box.cfg{replication_synchro_timeout = 1000, replication_synchro_quorum = 2}
+_ = box.schema.create_space('locallocal', {is_local = true})
+_ = _:create_index('pk')
+-- Propagate local vclock to some insane value to ensure it won't
+-- affect anything.
+box.begin() for i = 1, 2000 do box.space.locallocal:replace{1} end box.commit()
+do \
+ f1 = fiber.create(box.space.sync.replace, box.space.sync, {8}) \
+ f2 = fiber.create(box.space.locallocal.replace, box.space.locallocal, {8}) \
+ box.space.test:replace{8} \
+end
+f1:status()
+f2:status()
+box.space.sync:select{8}
+box.space.locallocal:select{8}
+box.space.test:select{8}
+
+test_run:switch('replica')
+box.space.sync:select{8}
+box.space.locallocal:select{8}
+box.space.test:select{8}
+
+-- Ensure sync rollback will affect all pending fully local async
+-- transactions too.
+test_run:switch('default')
+box.cfg{replication_synchro_timeout = 0.001, replication_synchro_quorum = 3}
+do \
+ f1 = fiber.create(box.space.sync.replace, box.space.sync, {9}) \
+ f2 = fiber.create(box.space.locallocal.replace, box.space.locallocal, {9}) \
+ box.space.test:replace{9} \
+end
+f1:status()
+f2:status()
+box.space.sync:select{9}
+box.space.locallocal:select{9}
+box.space.test:select{9}
+test_run:switch('replica')
+box.space.sync:select{9}
+box.space.locallocal:select{9}
+box.space.test:select{9}
+
--
-- gh-5123: quorum 1 still should write CONFIRM.
--
--
2.21.1 (Apple Git-122.3)
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