[Tarantool-patches] [PATCH v2 2/6] relay: introduce on_status_update trigger

[Serge Petrenko]

The trigger is fired from tx_status_update(), which is the notification
for tx that relay's vclock is updated.

The trigger will be used to collect synchronous transactions quorum for
old leader's transactions.

Part of #5435
---
 src/box/relay.cc | 12 ++++++++++++
 src/box/relay.h  |  4 ++++
 2 files changed, 16 insertions(+)

diff --git a/src/box/relay.cc b/src/box/relay.cc
index e16ac5a6b..dbad8a680 100644
--- a/src/box/relay.cc
+++ b/src/box/relay.cc
@@ -146,6 +146,8 @@ struct relay {
 		alignas(CACHELINE_SIZE)
 		/** Known relay vclock. */
 		struct vclock vclock;
+		/** Triggers fired once tx knows the new relay vclock. */
+		struct rlist on_status_update;
 		/**
 		 * True if the relay needs Raft updates. It can live fine
 		 * without sending Raft updates, if it is a relay to an
@@ -173,6 +175,12 @@ relay_vclock(const struct relay *relay)
 	return &relay->tx.vclock;
 }
 
+void
+relay_on_status_update(struct relay *relay, struct trigger *trigger)
+{
+	trigger_add(&relay->tx.on_status_update, trigger);
+}
+
 double
 relay_last_row_time(const struct relay *relay)
 {
@@ -201,6 +209,7 @@ relay_new(struct replica *replica)
 	diag_create(&relay->diag);
 	stailq_create(&relay->pending_gc);
 	relay->state = RELAY_OFF;
+	rlist_create(&relay->tx.on_status_update);
 	return relay;
 }
 
@@ -423,6 +432,9 @@ tx_status_update(struct cmsg *msg)
 		txn_limbo_ack(&txn_limbo, status->relay->replica->id,
 			      vclock_get(&status->vclock, instance_id));
 	}
+
+	trigger_run(&status->relay->tx.on_status_update, status->relay);
+
 	static const struct cmsg_hop route[] = {
 		{relay_status_update, NULL}
 	};
diff --git a/src/box/relay.h b/src/box/relay.h
index b32e2ea2a..4e6ecaffb 100644
--- a/src/box/relay.h
+++ b/src/box/relay.h
@@ -93,6 +93,10 @@ relay_vclock(const struct relay *relay);
 double
 relay_last_row_time(const struct relay *relay);
 
+/** Set a trigger on relay vclock update as seen by tx. */
+void
+relay_on_status_update(struct relay *relay, struct trigger *trigger);
+
 /**
  * Send a Raft update request to the relay channel. It is not
  * guaranteed that it will be delivered. The connection may break.
-- 
2.24.3 (Apple Git-128)