[tarantool-patches] [PATCH 4/5] test: set packet drop rate instead of flag in swim tests

[Vladislav Shpilevoy <v.shpilevoy@tarantool.org>]

Before dissemination component it was enough in the tests to
either drop all packets to/from a certain member, or do not drop
at all. But after dissemination it will be time to test more
granulated packet loss table: not 0/100, but 5/10/20/50/.../100
packet loss rate.

Part of #3234
---
 test/unit/swim.c                | 10 +++++-----
 test/unit/swim_test_transport.c | 27 +++++++++++++++++++--------
 test/unit/swim_test_transport.h |  9 +++++----
 test/unit/swim_test_utils.c     |  2 +-
 test/unit/swim_test_utils.h     |  2 +-
 5 files changed, 31 insertions(+), 19 deletions(-)

diff --git a/test/unit/swim.c b/test/unit/swim.c
index d77225f6c..358230e15 100644
--- a/test/unit/swim.c
+++ b/test/unit/swim.c
@@ -293,7 +293,7 @@ swim_test_basic_gossip(void)
 	 */
 	swim_cluster_add_link(cluster, 0, 1);
 	swim_cluster_add_link(cluster, 1, 0);
-	swim_cluster_set_drop(cluster, 1, true);
+	swim_cluster_set_drop(cluster, 1, 100);
 	/*
 	 * Wait two no-ACKs on S1 from S2. +1 sec to send a first
 	 * ping.
@@ -353,9 +353,9 @@ swim_test_refute(void)
 	swim_cluster_set_ack_timeout(cluster, 2);
 
 	swim_cluster_add_link(cluster, 0, 1);
-	swim_cluster_set_drop(cluster, 1, true);
+	swim_cluster_set_drop(cluster, 1, 100);
 	fail_if(swim_cluster_wait_status(cluster, 0, 1, MEMBER_DEAD, 7) != 0);
-	swim_cluster_set_drop(cluster, 1, false);
+	swim_cluster_set_drop(cluster, 1, 0);
 	is(swim_cluster_wait_incarnation(cluster, 1, 1, 1, 1), 0,
 	   "S2 increments its own incarnation to refute its death");
 	is(swim_cluster_wait_incarnation(cluster, 0, 1, 1, 1), 0,
@@ -390,7 +390,7 @@ swim_test_too_big_packet(void)
 	   "eventually reached", size);
 
 	swim_cluster_set_ack_timeout(cluster, ack_timeout);
-	swim_cluster_set_drop(cluster, drop_id, true);
+	swim_cluster_set_drop(cluster, drop_id, 100);
 	is(swim_cluster_wait_status_anywhere(cluster, drop_id, MEMBER_DEAD,
 					     first_dead_timeout), 0,
 	   "a dead member is detected in time not depending on cluster size");
@@ -426,7 +426,7 @@ swim_test_undead(void)
 	swim_cluster_set_ack_timeout(cluster, 1);
 	swim_cluster_add_link(cluster, 0, 1);
 	swim_cluster_add_link(cluster, 1, 0);
-	swim_cluster_set_drop(cluster, 1, true);
+	swim_cluster_set_drop(cluster, 1, 100);
 	is(swim_cluster_wait_status(cluster, 0, 1, MEMBER_DEAD, 4), 0,
 	   "member S2 is dead");
 	swim_run_for(5);
diff --git a/test/unit/swim_test_transport.c b/test/unit/swim_test_transport.c
index 3b59eaf4d..e563185ee 100644
--- a/test/unit/swim_test_transport.c
+++ b/test/unit/swim_test_transport.c
@@ -97,10 +97,10 @@ struct swim_fd {
 	 */
 	bool is_opened;
 	/**
-	 * True if any message sent to that fd should be just
-	 * dropped, not queued.
+	 * Probability of packet loss. For both sends and
+	 * receipts.
 	 */
-	bool is_dropping;
+	double drop_rate;
 	/**
 	 * Link in the list of opened and non-blocked descriptors.
 	 * Used to feed them all EV_WRITE.
@@ -130,7 +130,7 @@ swim_fd_open(struct swim_fd *fd)
 		return -1;
 	}
 	fd->is_opened = true;
-	fd->is_dropping = false;
+	fd->drop_rate = 0;
 	rlist_add_tail_entry(&swim_fd_active, fd, in_active);
 	return 0;
 }
@@ -156,7 +156,7 @@ swim_test_transport_init(void)
 	for (int i = 0, evfd = FAKE_FD_BASE; i < FAKE_FD_NUMBER; ++i, ++evfd) {
 		swim_fd[i].evfd = evfd;
 		swim_fd[i].is_opened = false;
-		swim_fd[i].is_dropping = false;
+		swim_fd[i].drop_rate = 0;
 		rlist_create(&swim_fd[i].in_active);
 		rlist_create(&swim_fd[i].recv_queue);
 		rlist_create(&swim_fd[i].send_queue);
@@ -268,11 +268,21 @@ swim_test_transport_unblock_fd(int fd)
 }
 
 void
-swim_test_transport_set_drop(int fd, bool value)
+swim_test_transport_set_drop(int fd, double value)
 {
 	struct swim_fd *sfd = &swim_fd[fd - FAKE_FD_BASE];
 	if (sfd->is_opened)
-		sfd->is_dropping = value;
+		sfd->drop_rate = value;
+}
+
+/**
+ * Returns true with probability @a rate, and is used to decided
+ * wether to drop a packet or not.
+ */
+static inline bool
+swim_test_is_drop(double rate)
+{
+	return ((double) rand() / RAND_MAX) * 100 < rate;
 }
 
 /** Send one packet to destination's recv queue. */
@@ -285,7 +295,8 @@ swim_fd_send_packet(struct swim_fd *fd)
 		rlist_shift_entry(&fd->send_queue, struct swim_test_packet,
 				  in_queue);
 	struct swim_fd *dst = &swim_fd[ntohs(p->dst.sin_port)];
-	if (dst->is_opened && ! dst->is_dropping && ! fd->is_dropping)
+	if (dst->is_opened && !swim_test_is_drop(dst->drop_rate) &&
+	    !swim_test_is_drop(fd->drop_rate))
 		rlist_add_tail_entry(&dst->recv_queue, p, in_queue);
 	else
 		swim_test_packet_delete(p);
diff --git a/test/unit/swim_test_transport.h b/test/unit/swim_test_transport.h
index 5a1a92271..d291abe91 100644
--- a/test/unit/swim_test_transport.h
+++ b/test/unit/swim_test_transport.h
@@ -60,12 +60,13 @@ void
 swim_test_transport_unblock_fd(int fd);
 
 /**
- * Set to true, if all incomming and outgoing packets should be
- * dropped. Note, that the node, owning @a fd, thinks, that its
- * packets are sent.
+ * Drop rate of incomming and outgoing packets. Note, that even if
+ * a packet is dropped on send, the node, owning @a fd, still
+ * thinks, that the packet is sent. It is not a sender-visible
+ * error.
  */
 void
-swim_test_transport_set_drop(int fd, bool value);
+swim_test_transport_set_drop(int fd, double value);
 
 /** Initialize test transport system. */
 void
diff --git a/test/unit/swim_test_utils.c b/test/unit/swim_test_utils.c
index 277a73498..bada8ef43 100644
--- a/test/unit/swim_test_utils.c
+++ b/test/unit/swim_test_utils.c
@@ -177,7 +177,7 @@ swim_cluster_unblock_io(struct swim_cluster *cluster, int i)
 }
 
 void
-swim_cluster_set_drop(struct swim_cluster *cluster, int i, bool value)
+swim_cluster_set_drop(struct swim_cluster *cluster, int i, double value)
 {
 	swim_test_transport_set_drop(swim_fd(cluster->node[i]), value);
 }
diff --git a/test/unit/swim_test_utils.h b/test/unit/swim_test_utils.h
index 6e99b4879..f4397aff4 100644
--- a/test/unit/swim_test_utils.h
+++ b/test/unit/swim_test_utils.h
@@ -80,7 +80,7 @@ void
 swim_cluster_unblock_io(struct swim_cluster *cluster, int i);
 
 void
-swim_cluster_set_drop(struct swim_cluster *cluster, int i, bool value);
+swim_cluster_set_drop(struct swim_cluster *cluster, int i, double value);
 
 /**
  * Explicitly add a member of id @a from_id to a member of id
-- 
2.17.2 (Apple Git-113)