[PATCH v2] iproto: report active connections number

[Ilya Kosarev <i.kosarev@tarantool.org>]

From: Ilya Kosarev <ilyanapar@yandex.ru>

Now there is new member in box.stat.net() called "CONNECTIONS"
which is a number of active iproto connections.

Closes #3905
---
https://github.com/tarantool/tarantool/tree/i.kosarev/gh-3905-report-connections-number
https://github.com/tarantool/tarantool/issues/3905

Changes in v2:
  - CONNECTIONS counter doesn't count rps any more
  - Test became much more thorough

 src/box/iproto.cc          | 17 +++++++++++++--
 src/box/lua/stat.c         | 44 +++++++++++++++++++++++++++++++++++++-
 test/box/stat_net.result   | 43 +++++++++++++++++++++++++++++++++++++
 test/box/stat_net.test.lua | 14 ++++++++++++
 4 files changed, 115 insertions(+), 3 deletions(-)

diff --git a/src/box/iproto.cc b/src/box/iproto.cc
index 863eb4f06..386bab239 100644
--- a/src/box/iproto.cc
+++ b/src/box/iproto.cc
@@ -263,14 +263,20 @@ static struct cord net_cord;
 static struct slab_cache net_slabc;
 
 struct rmean *rmean_net;
+struct rmean *rmean_connections;
 
 enum rmean_net_name {
 	IPROTO_SENT,
 	IPROTO_RECEIVED,
 	IPROTO_LAST,
 };
+enum rmean_connection_name {
+    IPROTO_CONNECTIONS,
+    IPROTO_CONNECTIONS_LAST,
+};
 
 const char *rmean_net_strings[IPROTO_LAST] = { "SENT", "RECEIVED" };
+const char *rmean_connection_strings[IPROTO_CONNECTIONS_LAST] = { "CONNECTIONS" };
 
 static void
 tx_process_destroy(struct cmsg *m);
@@ -579,6 +585,8 @@ iproto_connection_close(struct iproto_connection *con)
 		/* Make evio_has_fd() happy */
 		con->input.fd = con->output.fd = -1;
 		close(fd);
+		/* Count statistics */
+		rmean_collect(rmean_connections, IPROTO_CONNECTIONS, -1);
 		/*
 		 * Discard unparsed data, to recycle the
 		 * connection in net_send_msg() as soon as all
@@ -1858,6 +1866,8 @@ iproto_on_accept(struct evio_service * /* service */, int fd,
 	struct iproto_connection *con = iproto_connection_new(fd);
 	if (con == NULL)
 		return -1;
+	/* Count statistics */
+	rmean_collect(rmean_connections, IPROTO_CONNECTIONS, 1);
 	/*
 	 * Ignore msg allocation failure - the queue size is
 	 * fixed so there is a limited number of msgs in
@@ -1894,10 +1904,11 @@ net_cord_f(va_list /* ap */)
 			  iproto_on_accept, NULL);
 
 
-	/* Init statistics counter */
+	/* Init statistics counters */
 	rmean_net = rmean_new(rmean_net_strings, IPROTO_LAST);
+	rmean_connections = rmean_new(rmean_connection_strings, IPROTO_CONNECTIONS_LAST);
 
-	if (rmean_net == NULL) {
+	if (rmean_net == NULL or rmean_connections == NULL) {
 		tnt_raise(OutOfMemory, sizeof(struct rmean),
 			  "rmean", "struct rmean");
 	}
@@ -1921,6 +1932,7 @@ net_cord_f(va_list /* ap */)
 		evio_service_stop(&binary);
 
 	rmean_delete(rmean_net);
+	rmean_delete(rmean_connections);
 	return 0;
 }
 
@@ -2125,6 +2137,7 @@ void
 iproto_reset_stat(void)
 {
 	rmean_cleanup(rmean_net);
+	rmean_cleanup(rmean_connections);
 }
 
 void
diff --git a/src/box/lua/stat.c b/src/box/lua/stat.c
index 3fce81f61..f5b2ad7c1 100644
--- a/src/box/lua/stat.c
+++ b/src/box/lua/stat.c
@@ -50,6 +50,7 @@ extern struct rmean *rmean_box;
 extern struct rmean *rmean_error;
 /** network statistics (iproto & cbus) */
 extern struct rmean *rmean_net;
+extern struct rmean *rmean_connections;
 extern struct rmean *rmean_tx_wal_bus;
 
 static void
@@ -79,6 +80,29 @@ set_stat_item(const char *name, int rps, int64_t total, void *cb_ctx)
 	return 0;
 }
 
+static void
+fill_conn_item(struct lua_State *L, int64_t total)
+{
+	lua_pushstring(L, "total");
+	lua_pushnumber(L, total);
+	lua_settable(L, -3);
+}
+
+static int
+set_conn_item(const char *name, int rps, int64_t total, void *cb_ctx)
+{
+	struct lua_State *L = (struct lua_State *) cb_ctx;
+
+	lua_pushstring(L, name);
+	lua_newtable(L);
+
+	fill_conn_item(L, total);
+
+	lua_settable(L, -3);
+
+	return rps - rps;
+}
+
 /**
  * A stat_foreach() callback used to handle access to e.g.
  * box.stats.DELETE.
@@ -96,6 +120,19 @@ seek_stat_item(const char *name, int rps, int64_t total, void *cb_ctx)
 	return 1;
 }
 
+static int
+seek_conn_item(const char *name, int rps, int64_t total, void *cb_ctx)
+{
+	struct lua_State *L = (struct lua_State *) cb_ctx;
+	if (strcmp(name, lua_tostring(L, -1)) != 0)
+		return rps - rps;
+
+	lua_newtable(L);
+	fill_conn_item(L, total);
+
+	return 1;
+}
+
 static int
 lbox_stat_index(struct lua_State *L)
 {
@@ -140,7 +177,11 @@ static int
 lbox_stat_net_index(struct lua_State *L)
 {
 	luaL_checkstring(L, -1);
-	return rmean_foreach(rmean_net, seek_stat_item, L);
+	if (rmean_foreach(rmean_net, seek_stat_item, L) == 1)
+		return 1;
+	if (rmean_foreach(rmean_connections, seek_conn_item, L) == 1)
+		return 1;
+	return 0;
 }
 
 static int
@@ -148,6 +189,7 @@ lbox_stat_net_call(struct lua_State *L)
 {
 	lua_newtable(L);
 	rmean_foreach(rmean_net, set_stat_item, L);
+	rmean_foreach(rmean_connections, set_conn_item, L);
 	return 1;
 }
 
diff --git a/test/box/stat_net.result b/test/box/stat_net.result
index b3e3db11f..dad932f8c 100644
--- a/test/box/stat_net.result
+++ b/test/box/stat_net.result
@@ -28,12 +28,24 @@ index = space:create_index('primary', { type = 'hash' })
 remote = require 'net.box'
 ---
 ...
+fiber = require 'fiber'
+---
+...
 LISTEN = require('uri').parse(box.cfg.listen)
 ---
 ...
 cn = remote.connect(LISTEN.host, LISTEN.service)
 ---
 ...
+cn1 = remote.connect(LISTEN.host, LISTEN.service)
+---
+...
+cn2 = remote.connect(LISTEN.host, LISTEN.service)
+---
+...
+cn3 = remote.connect(LISTEN.host, LISTEN.service)
+---
+...
 cn.space.tweedledum:select() --small request
 ---
 - []
@@ -46,8 +58,35 @@ box.stat.net.RECEIVED.total > 0
 ---
 - true
 ...
+box.stat.net.CONNECTIONS.total == 4
+---
+- true
+...
 -- box.stat.net.EVENTS.total > 0
 -- box.stat.net.LOCKS.total > 0
+cn1:close()
+---
+...
+cn2:close()
+---
+...
+fiber.sleep(0.001)
+---
+...
+box.stat.net.CONNECTIONS.total == 2
+---
+- true
+...
+cn3:close()
+---
+...
+fiber.sleep(0.01)
+---
+...
+box.stat.net.CONNECTIONS.total == 1
+---
+- true
+...
 -- reset
 box.stat.reset()
 ---
@@ -60,6 +99,10 @@ box.stat.net.RECEIVED.total
 ---
 - 0
 ...
+box.stat.net.CONNECTIONS.total
+---
+- 0
+...
 space:drop() -- tweedledum
 ---
 ...
diff --git a/test/box/stat_net.test.lua b/test/box/stat_net.test.lua
index 808bb71e7..9b379f6dd 100644
--- a/test/box/stat_net.test.lua
+++ b/test/box/stat_net.test.lua
@@ -10,21 +10,35 @@ space = box.schema.space.create('tweedledum')
 box.schema.user.grant('guest', 'read', 'space', 'tweedledum')
 index = space:create_index('primary', { type = 'hash' })
 remote = require 'net.box'
+fiber = require 'fiber'
 
 LISTEN = require('uri').parse(box.cfg.listen)
 cn = remote.connect(LISTEN.host, LISTEN.service)
+cn1 = remote.connect(LISTEN.host, LISTEN.service)
+cn2 = remote.connect(LISTEN.host, LISTEN.service)
+cn3 = remote.connect(LISTEN.host, LISTEN.service)
 
 cn.space.tweedledum:select() --small request
 
 box.stat.net.SENT.total > 0
 box.stat.net.RECEIVED.total > 0
+box.stat.net.CONNECTIONS.total == 4
 -- box.stat.net.EVENTS.total > 0
 -- box.stat.net.LOCKS.total > 0
 
+cn1:close()
+cn2:close()
+fiber.sleep(0.001)
+box.stat.net.CONNECTIONS.total == 2
+cn3:close()
+fiber.sleep(0.01)
+box.stat.net.CONNECTIONS.total == 1
+
 -- reset
 box.stat.reset()
 box.stat.net.SENT.total
 box.stat.net.RECEIVED.total
+box.stat.net.CONNECTIONS.total
 
 space:drop() -- tweedledum
 cn:close()
-- 
2.17.1