[Tarantool-patches] [PATCH] replication: add support of qsync to the snapshot machinery
Leonid Vasiliev
lvasiliev at tarantool.org
Wed Jun 10 17:34:16 MSK 2020
To support qsync replication, the waiting for confirmation of
current "sync" transactions during a timeout has been added to
the snapshot machinery. In the case of rollback or the timeout
expiration, the snapshot will be cancelled.
Closes #4850
---
Dirty version without tests.
https://github.com/tarantool/tarantool/issues/4850
a part of https://github.com/tarantool/tarantool/tree/gh-4842-sync-replication
src/box/gc.c | 92 +++++++++++++++++++++++++++++++++++++++++++++++++++++
src/box/txn_limbo.h | 19 +++++++++++
2 files changed, 111 insertions(+)
diff --git a/src/box/gc.c b/src/box/gc.c
index 8e8ffea..fb7b37a 100644
--- a/src/box/gc.c
+++ b/src/box/gc.c
@@ -57,6 +57,9 @@
#include "engine.h" /* engine_collect_garbage() */
#include "wal.h" /* wal_collect_garbage() */
#include "checkpoint_schedule.h"
+#include "trigger.h"
+#include "txn.h"
+#include "txn_limbo.h"
struct gc_state gc;
@@ -65,6 +68,26 @@ gc_cleanup_fiber_f(va_list);
static int
gc_checkpoint_fiber_f(va_list);
+//TODO: quorum timeout should be used instead
+double snap_confirm_timeout = 5.0; /* seconds */
+
+/**
+ * Waitpoint stores information about the progress of confirmation.
+ * In the case of multimaster support, it will store a bitset
+ * or array instead of the boolean.
+ */
+struct confirm_waitpoint {
+ /**
+ * Variable for wake up the fiber that is waiting for
+ * the end of confirmation.
+ */
+ struct fiber_cond confirm_cond;
+ /**
+ * Result flag.
+ */
+ bool is_confirm;
+};
+
/**
* Comparator used for ordering gc_consumer objects
* lexicographically by their vclock in a binary tree.
@@ -377,6 +400,64 @@ gc_add_checkpoint(const struct vclock *vclock)
}
static int
+gc_txn_commit_cb(struct trigger *trigger, void *event)
+{
+ (void)event;
+ struct confirm_waitpoint *cwp =
+ (struct confirm_waitpoint *)trigger->data;
+ cwp->is_confirm = true;
+ fiber_cond_signal(&cwp->confirm_cond);
+ return 0;
+}
+
+static int
+gc_txn_rollback_cb(struct trigger *trigger, void *event)
+{
+ (void)event;
+ struct confirm_waitpoint *cwp =
+ (struct confirm_waitpoint *)trigger->data;
+ fiber_cond_signal(&cwp->confirm_cond);
+ return 0;
+}
+
+/**
+ * Waiting for confirmation of all "sync" transactions
+ * during snap_confirm_timeout or fail.
+ */
+static int
+gc_wait_confirm(void)
+{
+ /* initialization of a waitpoint. */
+ struct confirm_waitpoint cwp;
+ fiber_cond_create(&cwp.confirm_cond);
+ cwp.is_confirm = false;
+
+ /* Set triggers for the last limbo transaction. */
+ struct trigger on_complete;
+ trigger_create(&on_complete, gc_txn_commit_cb, &cwp, NULL);
+ struct trigger on_rollback;
+ trigger_create(&on_rollback, gc_txn_rollback_cb, &cwp, NULL);
+ struct txn_limbo_entry *tle = txn_limbo_last_entry(&txn_limbo);
+ txn_on_commit(tle->txn, &on_complete);
+ txn_on_rollback(tle->txn, &on_rollback);
+
+ int rc = fiber_cond_wait_timeout(&cwp.confirm_cond,
+ snap_confirm_timeout);
+ fiber_cond_destroy(&cwp.confirm_cond);
+ if (rc != 0) {
+ /* Clear the triggers if the timeout has been reached. */
+ trigger_clear(&on_complete);
+ trigger_clear(&on_rollback);
+ return -1;
+ }
+ if (!cwp.is_confirm) {
+ /* The transaction has been rollbacked. */
+ return -1;
+ }
+ return 0;
+}
+
+static int
gc_do_checkpoint(bool is_scheduled)
{
int rc;
@@ -395,6 +476,17 @@ gc_do_checkpoint(bool is_scheduled)
rc = wal_begin_checkpoint(&checkpoint);
if (rc != 0)
goto out;
+
+ /*
+ * Wait the confirms on all "sync" transactions before
+ * create a snapshot.
+ */
+ if (!txn_limbo_is_empty(&txn_limbo)) {
+ rc = gc_wait_confirm();
+ if (rc != 0)
+ goto out;
+ }
+
rc = engine_commit_checkpoint(&checkpoint.vclock);
if (rc != 0)
goto out;
diff --git a/src/box/txn_limbo.h b/src/box/txn_limbo.h
index de415cd..c0b821a 100644
--- a/src/box/txn_limbo.h
+++ b/src/box/txn_limbo.h
@@ -166,6 +166,25 @@ txn_limbo_wait_complete(struct txn_limbo *limbo, struct txn_limbo_entry *entry);
void
txn_limbo_read_confirm(struct txn_limbo *limbo, int64_t lsn);
+/**
+ * Return TRUE if limbo is empty.
+ */
+static inline bool
+txn_limbo_is_empty(struct txn_limbo *limbo)
+{
+ return rlist_empty(&limbo->queue);
+}
+
+/**
+ * Return a pointer to the last txn_limbo_entry of limbo.
+ */
+static inline struct txn_limbo_entry *
+txn_limbo_last_entry(struct txn_limbo *limbo)
+{
+ return rlist_last_entry(&limbo->queue, struct txn_limbo_entry,
+ in_queue);
+}
+
void
txn_limbo_init();
--
2.7.4
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