From ce0a83eb46cb0666e41d010e24e595874a4c2017 Mon Sep 17 00:00:00 2001
From: Serge Petrenko <sergepetrenko@tarantool.org>
Date: Wed, 15 Jun 2022 15:21:50 +0300
Subject: [PATCH] txn_limbo: rework limbo->frozen flag
Soon there will be more reasons for a transaction limbo to be frozen.
Let's make the limbo->frozen flag a bitmap and rename it to
limno->frozen_reasons.
The first bit, named frozen_due_to_fencing, represents the only current
reason for the limbo to be frozen.
While we are at it, rename txn_limbo_(un)freeze to txn_limbo_(un)fence
to better reflect the situation.
Part-of #5295
NO_DOC=refactoring
NO_TEST=refactoring
NO_CHANGELOG=refactoring
---
src/box/raft.c | 4 ++--
src/box/txn_limbo.c | 26 ++++++++++++++++----------
src/box/txn_limbo.h | 32 ++++++++++++++++++++++----------
3 files changed, 40 insertions(+), 22 deletions(-)
diff --git a/src/box/raft.c b/src/box/raft.c
index fb518538ea..25da3f5df9 100644
--- a/src/box/raft.c
+++ b/src/box/raft.c
@@ -287,7 +287,7 @@ box_raft_fence(void)
!election_fencing_enabled || box_raft_election_fencing_paused)
return;
- txn_limbo_freeze(&txn_limbo);
+ txn_limbo_fence(&txn_limbo);
raft_resign(raft);
}
@@ -563,7 +563,7 @@ box_raft_set_election_fencing_enabled(bool enabled)
election_fencing_enabled = enabled;
say_info("RAFT: fencing %s", enabled ? "enabled" : "disabled");
if (!enabled)
- txn_limbo_unfreeze(&txn_limbo);
+ txn_limbo_unfence(&txn_limbo);
replicaset_on_health_change();
}
diff --git a/src/box/txn_limbo.c b/src/box/txn_limbo.c
index 8fc953e250..791c68f566 100644
--- a/src/box/txn_limbo.c
+++ b/src/box/txn_limbo.c
@@ -52,13 +52,19 @@ txn_limbo_create(struct txn_limbo *limbo)
limbo->rollback_count = 0;
limbo->is_in_rollback = false;
limbo->svp_confirmed_lsn = -1;
- limbo->frozen = false;
+ limbo->frozen_reasons = 0;
+}
+
+static inline bool
+txn_limbo_is_frozen(const struct txn_limbo *limbo)
+{
+ return limbo->frozen_reasons != 0;
}
bool
txn_limbo_is_ro(struct txn_limbo *limbo)
{
- return limbo->frozen ||
+ return txn_limbo_is_frozen(limbo) ||
(limbo->owner_id != REPLICA_ID_NIL &&
limbo->owner_id != instance_id);
}
@@ -237,7 +243,7 @@ txn_limbo_wait_complete(struct txn_limbo *limbo, struct txn_limbo_entry *entry)
double deadline = start_time + replication_synchro_timeout;
double timeout = deadline - fiber_clock();
int rc = fiber_cond_wait_timeout(&limbo->wait_cond, timeout);
- if (limbo->frozen)
+ if (txn_limbo_is_frozen(limbo))
goto wait;
if (txn_limbo_entry_is_complete(entry))
goto complete;
@@ -586,7 +592,7 @@ txn_limbo_ack(struct txn_limbo *limbo, uint32_t replica_id, int64_t lsn)
{
if (rlist_empty(&limbo->queue))
return;
- if (limbo->frozen)
+ if (txn_limbo_is_frozen(limbo))
return;
assert(!txn_limbo_is_ro(limbo));
/*
@@ -849,7 +855,7 @@ txn_limbo_req_commit(struct txn_limbo *limbo, const struct synchro_request *req)
if (term > limbo->promote_greatest_term) {
limbo->promote_greatest_term = term;
if (iproto_type_is_promote_request(req->type))
- txn_limbo_unfreeze(&txn_limbo);
+ txn_limbo_unfence(&txn_limbo);
}
} else if (iproto_type_is_promote_request(req->type) &&
limbo->promote_greatest_term > 1) {
@@ -918,7 +924,7 @@ txn_limbo_process(struct txn_limbo *limbo, const struct synchro_request *req)
void
txn_limbo_on_parameters_change(struct txn_limbo *limbo)
{
- if (rlist_empty(&limbo->queue) || limbo->frozen)
+ if (rlist_empty(&limbo->queue) || txn_limbo_is_frozen(limbo))
return;
struct txn_limbo_entry *e;
int64_t confirm_lsn = -1;
@@ -948,16 +954,16 @@ txn_limbo_on_parameters_change(struct txn_limbo *limbo)
}
void
-txn_limbo_freeze(struct txn_limbo *limbo)
+txn_limbo_fence(struct txn_limbo *limbo)
{
- limbo->frozen = true;
+ limbo->is_frozen_due_to_fencing = true;
box_update_ro_summary();
}
void
-txn_limbo_unfreeze(struct txn_limbo *limbo)
+txn_limbo_unfence(struct txn_limbo *limbo)
{
- limbo->frozen = false;
+ limbo->is_frozen_due_to_fencing = false;
box_update_ro_summary();
}
diff --git a/src/box/txn_limbo.h b/src/box/txn_limbo.h
index 7db69563d1..095c965a0c 100644
--- a/src/box/txn_limbo.h
+++ b/src/box/txn_limbo.h
@@ -189,14 +189,26 @@ struct txn_limbo {
* synchro command (promote/demote/...) fails.
*/
int64_t svp_confirmed_lsn;
- /**
- * Whether the limbo is frozen. This mode prevents CONFIRMs and
- * ROLLBACKs being written by this instance. This mode is turned on when
- * quorum is lost if this instance is the current RAFT leader and
- * fencing is enabled. Instance leaves this mode when it becomes leader
- * again or PROMOTE/DEMOTE arrives from some remote instance.
- */
- bool frozen;
+ union {
+ /**
+ * Whether the limbo is frozen. This mode prevents CONFIRMs and
+ * ROLLBACKs being written by this instance. This, in turn,
+ * helps to prevent split-brain situations, when a node
+ * finalizes some transaction before knowing that the
+ * transaction was already finalized by someone else.
+ */
+ uint8_t frozen_reasons;
+ struct {
+ /*
+ * This mode is turned on when quorum is lost if this
+ * instance is the current RAFT leader and fencing is
+ * enabled. Instance leaves this mode when it becomes
+ * leader again or PROMOTE/DEMOTE arrives from some
+ * remote instance.
+ */
+ bool is_frozen_due_to_fencing : 1;
+ };
+ };
};
/**
@@ -413,13 +425,13 @@ txn_limbo_on_parameters_change(struct txn_limbo *limbo);
* Freeze limbo. Prevent CONFIRMs and ROLLBACKs until limbo is unfrozen.
*/
void
-txn_limbo_freeze(struct txn_limbo *limbo);
+txn_limbo_fence(struct txn_limbo *limbo);
/**
* Unfreeze limbo. Continue limbo processing as usual.
*/
void
-txn_limbo_unfreeze(struct txn_limbo *limbo);
+txn_limbo_unfence(struct txn_limbo *limbo);
/**
* Initialize qsync engine.
--
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