From 43d429697d5ddf0151d0ff95072e3455c79b9359 Mon Sep 17 00:00:00 2001
From: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Date: Wed, 14 Oct 2020 00:46:14 +0200
Subject: [PATCH] raft: introduce on_update trigger
Raft state machine now has a trigger invoked each time when any of
the visible Raft attributes is changed: state, term, vote.
The trigger is needed to commit synchronous transactions of an old
leader, when a new leader is elected. This is done via a trigger
so as not to depend on box in raft code too much. That would make
it harder to extract it into a new module later.
The trigger is executed in the Raft worker fiber, so as not to
stop the state machine transitions anywhere, which currently don't
contain a single yield. And the synchronous transaction queue
clearance requires a yield, to write CONFIRM and ROLLBACK records
to WAL.
Part of #5339
---
src/box/raft.c | 8 ++++++++
src/box/raft.h | 13 +++++++++++++
2 files changed, 21 insertions(+)
diff --git a/src/box/raft.c b/src/box/raft.c
index c4d393c3ab..24f65ada7d 100644
--- a/src/box/raft.c
+++ b/src/box/raft.c
@@ -643,6 +643,7 @@ raft_worker_handle_broadcast(void)
}
replicaset_foreach(replica)
relay_push_raft(replica->relay, &req);
+ trigger_run(&raft.on_update, NULL);
raft.is_broadcast_scheduled = false;
}
@@ -903,6 +904,12 @@ raft_serialize_for_disk(struct raft_request *req)
req->vote = raft.vote;
}
+void
+raft_on_update(struct trigger *trigger)
+{
+ trigger_add(&raft.on_update, trigger);
+}
+
void
raft_cfg_is_enabled(bool is_enabled)
{
@@ -1040,4 +1047,5 @@ void
raft_init(void)
{
ev_timer_init(&raft.timer, raft_sm_schedule_new_election_cb, 0, 0);
+ rlist_create(&raft.on_update);
}
diff --git a/src/box/raft.h b/src/box/raft.h
index be77a54737..82d5aa4428 100644
--- a/src/box/raft.h
+++ b/src/box/raft.h
@@ -32,6 +32,7 @@
#include <stdint.h>
#include <stdbool.h>
#include "tarantool_ev.h"
+#include "trigger.h"
#if defined(__cplusplus)
extern "C" {
@@ -150,6 +151,11 @@ struct raft {
struct fiber *worker;
/** Configured election timeout in seconds. */
double election_timeout;
+ /**
+ * Trigger invoked each time any of the Raft node visible attributes are
+ * changed.
+ */
+ struct rlist on_update;
};
extern struct raft raft;
@@ -251,6 +257,13 @@ raft_serialize_for_network(struct raft_request *req, struct vclock *vclock);
void
raft_serialize_for_disk(struct raft_request *req);
+/**
+ * Add a trigger invoked each time any of the Raft node visible attributes are
+ * changed.
+ */
+void
+raft_on_update(struct trigger *trigger);
+
/** Initialize Raft global data structures. */
void
raft_init(void);
--
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