[PATCH v3 06/11] Include oldest vclock available on the instance in IPROTO_STATUS

[Vladimir Davydov <vdavydov.dev@gmail.com>]

It will be used to check if a replica fell too much behind its peers and
so needs to be rebootstrapped.

Needed for #461
---
 src/box/box.cc             |  1 +
 src/box/gc.c               |  6 ++++++
 src/box/gc.h               |  6 ++++++
 src/box/iproto_constants.h |  1 +
 src/box/xrow.c             | 13 ++++++++++---
 src/box/xrow.h             |  2 ++
 6 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/src/box/box.cc b/src/box/box.cc
index 7aac0a13..b629a4d8 100644
--- a/src/box/box.cc
+++ b/src/box/box.cc
@@ -1569,6 +1569,7 @@ box_process_status_request(struct status *status)
 {
 	status->is_ro = cfg_geti("read_only") != 0;
 	vclock_copy(&status->vclock, &replicaset.vclock);
+	gc_vclock(&status->gc_vclock);
 }
 
 /** Insert a new cluster into _schema */
diff --git a/src/box/gc.c b/src/box/gc.c
index 6c324220..bf221274 100644
--- a/src/box/gc.c
+++ b/src/box/gc.c
@@ -164,6 +164,12 @@ gc_free(void)
 	latch_destroy(&gc.latch);
 }
 
+void
+gc_vclock(struct vclock *vclock)
+{
+	vclock_copy(vclock, &gc.wal_vclock);
+}
+
 /** Find the consumer that uses the oldest checkpoint. */
 struct gc_consumer *
 gc_tree_first_checkpoint(gc_tree_t *consumers)
diff --git a/src/box/gc.h b/src/box/gc.h
index 7e061768..e8ee2d09 100644
--- a/src/box/gc.h
+++ b/src/box/gc.h
@@ -60,6 +60,12 @@ void
 gc_free(void);
 
 /**
+ * Get the oldest available vclock.
+ */
+void
+gc_vclock(struct vclock *vclock);
+
+/**
  * Invoke garbage collection in order to remove files left
  * from old checkpoints. The number of checkpoints saved by
  * this function is specified by box.cfg.checkpoint_count.
diff --git a/src/box/iproto_constants.h b/src/box/iproto_constants.h
index fe452817..e2bea886 100644
--- a/src/box/iproto_constants.h
+++ b/src/box/iproto_constants.h
@@ -87,6 +87,7 @@ enum iproto_key {
 enum iproto_status_key {
 	IPROTO_STATUS_IS_RO = 0x01,
 	IPROTO_STATUS_VCLOCK = 0x02,
+	IPROTO_STATUS_GC_VCLOCK = 0x03,
 };
 
 #define bit(c) (1ULL<<IPROTO_##c)
diff --git a/src/box/xrow.c b/src/box/xrow.c
index 8a87fd4d..345c7391 100644
--- a/src/box/xrow.c
+++ b/src/box/xrow.c
@@ -344,9 +344,10 @@ iproto_reply_status(struct obuf *out, const struct status *status,
 		    uint64_t sync, uint32_t schema_version)
 {
 	size_t max_size = IPROTO_HEADER_LEN + mp_sizeof_map(1) +
-		mp_sizeof_uint(UINT32_MAX) + mp_sizeof_map(2) +
+		mp_sizeof_uint(UINT32_MAX) + mp_sizeof_map(3) +
 		mp_sizeof_uint(UINT32_MAX) + mp_sizeof_bool(status->is_ro) +
-		mp_sizeof_uint(UINT32_MAX) + mp_sizeof_vclock(&status->vclock);
+		mp_sizeof_uint(UINT32_MAX) + mp_sizeof_vclock(&status->vclock) +
+		mp_sizeof_uint(UINT32_MAX) + mp_sizeof_vclock(&status->gc_vclock);
 
 	char *buf = obuf_reserve(out, max_size);
 	if (buf == NULL) {
@@ -358,11 +359,13 @@ iproto_reply_status(struct obuf *out, const struct status *status,
 	char *data = buf + IPROTO_HEADER_LEN;
 	data = mp_encode_map(data, 1);
 	data = mp_encode_uint(data, IPROTO_STATUS);
-	data = mp_encode_map(data, 2);
+	data = mp_encode_map(data, 3);
 	data = mp_encode_uint(data, IPROTO_STATUS_IS_RO);
 	data = mp_encode_bool(data, status->is_ro);
 	data = mp_encode_uint(data, IPROTO_STATUS_VCLOCK);
 	data = mp_encode_vclock(data, &status->vclock);
+	data = mp_encode_uint(data, IPROTO_STATUS_GC_VCLOCK);
+	data = mp_encode_vclock(data, &status->gc_vclock);
 	size_t size = data - buf;
 	assert(size <= max_size);
 
@@ -933,6 +936,10 @@ xrow_decode_status(struct xrow_header *row, struct status *status)
 			if (mp_decode_vclock(&data, &status->vclock) != 0)
 				goto err;
 			break;
+		case IPROTO_STATUS_GC_VCLOCK:
+			if (mp_decode_vclock(&data, &status->gc_vclock) != 0)
+				goto err;
+			break;
 		default:
 			mp_next(&data);
 		}
diff --git a/src/box/xrow.h b/src/box/xrow.h
index 1ea30fb1..341385d1 100644
--- a/src/box/xrow.h
+++ b/src/box/xrow.h
@@ -229,6 +229,8 @@ struct status {
 	bool is_ro;
 	/** Current instance vclock. */
 	struct vclock vclock;
+	/** Oldest vclock available on the instance. */
+	struct vclock gc_vclock;
 };
 
 /**
-- 
2.11.0