[Tarantool-patches] [PATCH] iproto: make iproto thread more independent from tx

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

On connection, an evio service callback is invoked to accept it. The
next step after acception was to process connection to tx thread
through cbus. This meant that any connection interaction involves
tx thread even before we get to decode what does the client want
from us. Consequently, a number of problems appears. The main one
is that we might get descriptor leak in case of unresponsive tx thread
(for example, when building secondary index). There are some other
cases where we might not want to spend precious tx time to process
the connection in case iproto can do it all alone.
This patch allows iproto to accept connection and send greeting by
itself. The connection is initialized in tx thread when the real
request comes through iproto_msg_decode(). In case request type was not
recognized we can also send reply with an error without using tx. It is
planned to add more iproto logic to prevent extra interaction with
tx thread. This patch already to some extent solves descriptors leakage
problem as far as connection establishes and stays in fetch_schema
state while tx thread is unresponsive.
The other user visible change is that on_connect triggers won't run on
connections that don't provide any input, as reflected in
bad_trigger.test.py.

Part of #3776
---
Branch: https://github.com/tarantool/tarantool/tree/i.kosarev/gh-3776-handling-connections-in-iproto
Issue: https://github.com/tarantool/tarantool/issues/3776

 src/box/iproto.cc               | 287 ++++++++++++++++++++------------
 test/box-py/bad_trigger.result  |   1 +
 test/box-py/bad_trigger.test.py |  22 ++-
 3 files changed, 202 insertions(+), 108 deletions(-)

diff --git a/src/box/iproto.cc b/src/box/iproto.cc
index b8f65e5eca..a027d15c1d 100644
--- a/src/box/iproto.cc
+++ b/src/box/iproto.cc
@@ -245,7 +245,7 @@ iproto_msg_new(struct iproto_connection *con);
 static void
 iproto_resume(void);
 
-static void
+static int
 iproto_msg_decode(struct iproto_msg *msg, const char **pos, const char *reqend,
 		  bool *stop_input);
 
@@ -256,6 +256,9 @@ iproto_msg_delete(struct iproto_msg *msg)
 	iproto_resume();
 }
 
+static inline void
+iproto_connection_delete(struct iproto_connection *con);
+
 /**
  * A single global queue for all requests in all connections. All
  * requests from all connections are processed concurrently.
@@ -280,6 +283,11 @@ static struct cord net_cord;
  * in the tx thread.
  */
 static struct slab_cache net_slabc;
+/**
+ * Slab cache used for allocating memory for output network buffers
+ * in the iproto thread.
+ */
+static struct slab_cache iproto_slabc;
 
 struct rmean *rmean_net;
 
@@ -298,6 +306,9 @@ const char *rmean_net_strings[IPROTO_LAST] = {
 	"REQUESTS",
 };
 
+static int
+tx_init_connect(struct iproto_msg *msg);
+
 static void
 tx_process_destroy(struct cmsg *m);
 
@@ -650,7 +661,18 @@ iproto_connection_try_to_start_destroy(struct iproto_connection *con)
 	 * other parts of the connection.
 	 */
 	con->state = IPROTO_CONNECTION_DESTROYED;
-	cpipe_push(&tx_pipe, &con->destroy_msg);
+	if (con->session != NULL)
+		cpipe_push(&tx_pipe, &con->destroy_msg);
+	else {
+		/*
+		* In case session was not created we can safely destroy
+		* not involving tx thread. Thus we also need to destroy
+		* obuf, which still belongs to iproto thread.
+		*/
+		obuf_destroy(&con->obuf[0]);
+		obuf_destroy(&con->obuf[1]);
+		iproto_connection_delete(con);
+	}
 }
 
 /**
@@ -677,9 +699,18 @@ iproto_connection_close(struct iproto_connection *con)
 		 * is done only once.
 		 */
 		con->p_ibuf->wpos -= con->parse_size;
-		cpipe_push(&tx_pipe, &con->disconnect_msg);
 		assert(con->state == IPROTO_CONNECTION_ALIVE);
 		con->state = IPROTO_CONNECTION_CLOSED;
+		rlist_del(&con->in_stop_list);
+		if (con->session != NULL)
+			cpipe_push(&tx_pipe, &con->disconnect_msg);
+		else
+			/*
+			* In case session was not created we can safely
+			* try to start destroy not involving tx thread.
+			*/
+			iproto_connection_try_to_start_destroy(con);
+		return;
 	} else if (con->state == IPROTO_CONNECTION_PENDING_DESTROY) {
 		iproto_connection_try_to_start_destroy(con);
 	} else {
@@ -809,6 +840,7 @@ iproto_enqueue_batch(struct iproto_connection *con, struct ibuf *in)
 	assert(rlist_empty(&con->in_stop_list));
 	int n_requests = 0;
 	bool stop_input = false;
+	bool obuf_in_iproto = (con->session == NULL);
 	const char *errmsg;
 	while (con->parse_size != 0 && !stop_input) {
 		if (iproto_check_msg_max()) {
@@ -853,12 +885,20 @@ err_msgpack:
 
 		msg->len = reqend - reqstart; /* total request length */
 
-		iproto_msg_decode(msg, &pos, reqend, &stop_input);
-		/*
-		 * This can't throw, but should not be
-		 * done in case of exception.
-		 */
-		cpipe_push_input(&tx_pipe, &msg->base);
+		if (iproto_msg_decode(msg, &pos, reqend, &stop_input) == 0) {
+			if (obuf_in_iproto) {
+				/*
+				* If session was not created yet and obuf is
+				* still in iproto we need to destroy it. New
+				* one will be created in tx thread if needed.
+				*/
+				obuf_destroy(&con->obuf[0]);
+				obuf_destroy(&con->obuf[1]);
+				obuf_in_iproto = false;
+			}
+			cpipe_push_input(&tx_pipe, &msg->base);
+		}
+
 		n_requests++;
 		/* Request is parsed */
 		assert(reqend > reqstart);
@@ -1105,8 +1145,8 @@ iproto_connection_new(int fd)
 	ev_io_init(&con->output, iproto_connection_on_output, fd, EV_WRITE);
 	ibuf_create(&con->ibuf[0], cord_slab_cache(), iproto_readahead);
 	ibuf_create(&con->ibuf[1], cord_slab_cache(), iproto_readahead);
-	obuf_create(&con->obuf[0], &net_slabc, iproto_readahead);
-	obuf_create(&con->obuf[1], &net_slabc, iproto_readahead);
+	obuf_create(&con->obuf[0], &iproto_slabc, iproto_readahead);
+	obuf_create(&con->obuf[1], &iproto_slabc, iproto_readahead);
 	con->p_ibuf = &con->ibuf[0];
 	con->tx.p_obuf = &con->obuf[0];
 	iproto_wpos_create(&con->wpos, con->tx.p_obuf);
@@ -1134,10 +1174,6 @@ iproto_connection_delete(struct iproto_connection *con)
 	assert(!evio_has_fd(&con->input));
 	assert(con->session == NULL);
 	assert(con->state == IPROTO_CONNECTION_DESTROYED);
-	/*
-	 * The output buffers must have been deleted
-	 * in tx thread.
-	 */
 	ibuf_destroy(&con->ibuf[0]);
 	ibuf_destroy(&con->ibuf[1]);
 	assert(con->obuf[0].pos == 0 &&
@@ -1172,6 +1208,9 @@ tx_reply_error(struct iproto_msg *msg);
 static void
 tx_reply_iproto_error(struct cmsg *m);
 
+static void
+tx_accept_wpos(struct iproto_connection *con, const struct iproto_wpos *wpos);
+
 static void
 net_send_msg(struct cmsg *msg);
 
@@ -1244,7 +1283,7 @@ static const struct cmsg_hop error_route[] = {
 	{ net_send_error, NULL },
 };
 
-static void
+static int
 iproto_msg_decode(struct iproto_msg *msg, const char **pos, const char *reqend,
 		  bool *stop_input)
 {
@@ -1314,13 +1353,27 @@ iproto_msg_decode(struct iproto_msg *msg, const char **pos, const char *reqend,
 			 (uint32_t) type);
 		goto error;
 	}
-	return;
+	return 0;
 error:
 	/** Log and send the error. */
 	diag_log();
 	diag_create(&msg->diag);
 	diag_move(&fiber()->diag, &msg->diag);
-	cmsg_init(&msg->base, error_route);
+	if (msg->connection->session != NULL) {
+		cmsg_init(&msg->base, error_route);
+		return 0;
+	}
+	/*
+	* In case session was not created we can process error path
+	* without tx thread.
+	*/
+	tx_accept_wpos(msg->connection, &msg->wpos);
+	struct obuf *out = msg->connection->tx.p_obuf;
+	iproto_reply_error(out, diag_last_error(&msg->diag),
+			   msg->header.sync, ::schema_version);
+	iproto_wpos_create(&msg->wpos, out);
+	net_send_error(&(msg->base));
+	return -1;
 }
 
 static void
@@ -1382,10 +1435,6 @@ tx_process_destroy(struct cmsg *m)
 		session_destroy(con->session);
 		con->session = NULL; /* safety */
 	}
-	/*
-	 * Got to be done in iproto thread since
-	 * that's where the memory is allocated.
-	 */
 	obuf_destroy(&con->obuf[0]);
 	obuf_destroy(&con->obuf[1]);
 }
@@ -1478,13 +1527,21 @@ tx_accept_wpos(struct iproto_connection *con, const struct iproto_wpos *wpos)
 	}
 }
 
-static inline struct iproto_msg *
-tx_accept_msg(struct cmsg *m)
+static inline int
+tx_accept_msg(struct cmsg *m, struct iproto_msg **msg)
 {
-	struct iproto_msg *msg = (struct iproto_msg *) m;
-	tx_accept_wpos(msg->connection, &msg->wpos);
-	tx_fiber_init(msg->connection->session, msg->header.sync);
-	return msg;
+	*msg = (struct iproto_msg *) m;
+	/*
+	* In case session was not created we need to init connection in tx and
+	* create it here.
+	*/
+	if ((*msg)->connection->session == NULL && tx_init_connect(*msg) != 0) {
+		(*msg)->close_connection = true;
+		return -1;
+	}
+	tx_accept_wpos((*msg)->connection, &(*msg)->wpos);
+	tx_fiber_init((*msg)->connection->session, (*msg)->header.sync);
+	return 0;
 }
 
 /**
@@ -1507,7 +1564,8 @@ tx_reply_error(struct iproto_msg *msg)
 static void
 tx_reply_iproto_error(struct cmsg *m)
 {
-	struct iproto_msg *msg = tx_accept_msg(m);
+	struct iproto_msg *msg;
+	tx_accept_msg(m, &msg);
 	struct obuf *out = msg->connection->tx.p_obuf;
 	iproto_reply_error(out, diag_last_error(&msg->diag),
 			   msg->header.sync, ::schema_version);
@@ -1527,7 +1585,9 @@ tx_inject_delay(void)
 static void
 tx_process1(struct cmsg *m)
 {
-	struct iproto_msg *msg = tx_accept_msg(m);
+	struct iproto_msg *msg;
+	if (tx_accept_msg(m, &msg) != 0)
+		goto error;
 	if (tx_check_schema(msg->header.schema_version))
 		goto error;
 
@@ -1553,17 +1613,20 @@ error:
 static void
 tx_process_select(struct cmsg *m)
 {
-	struct iproto_msg *msg = tx_accept_msg(m);
+	struct iproto_msg *msg;
+	struct request *req;
 	struct obuf *out;
 	struct obuf_svp svp;
 	struct port port;
 	int count;
 	int rc;
-	struct request *req = &msg->dml;
+	if (tx_accept_msg(m, &msg) != 0)
+		goto error;
 	if (tx_check_schema(msg->header.schema_version))
 		goto error;
 
 	tx_inject_delay();
+	req = &msg->dml;
 	rc = box_select(req->space_id, req->index_id,
 			req->iterator, req->offset, req->limit,
 			req->key, req->key_end, &port);
@@ -1607,7 +1670,9 @@ tx_process_call_on_yield(struct trigger *trigger, void *event)
 static void
 tx_process_call(struct cmsg *m)
 {
-	struct iproto_msg *msg = tx_accept_msg(m);
+	struct iproto_msg *msg;
+	if (tx_accept_msg(m, &msg) != 0)
+		goto error;
 	if (tx_check_schema(msg->header.schema_version))
 		goto error;
 
@@ -1686,13 +1751,15 @@ error:
 static void
 tx_process_misc(struct cmsg *m)
 {
-	struct iproto_msg *msg = tx_accept_msg(m);
-	struct iproto_connection *con = msg->connection;
-	struct obuf *out = con->tx.p_obuf;
+	struct iproto_msg *msg;
+	if (tx_accept_msg(m, &msg) != 0)
+		goto error;
 	if (tx_check_schema(msg->header.schema_version))
 		goto error;
 
 	try {
+		struct iproto_connection *con = msg->connection;
+		struct obuf *out = con->tx.p_obuf;
 		struct ballot ballot;
 		switch (msg->header.type) {
 		case IPROTO_AUTH:
@@ -1729,7 +1796,7 @@ error:
 static void
 tx_process_sql(struct cmsg *m)
 {
-	struct iproto_msg *msg = tx_accept_msg(m);
+	struct iproto_msg *msg;
 	struct obuf *out;
 	struct port port;
 	struct sql_bind *bind = NULL;
@@ -1738,6 +1805,8 @@ tx_process_sql(struct cmsg *m)
 	uint32_t len;
 	bool is_unprepare = false;
 
+	if (tx_accept_msg(m, &msg) != 0)
+		goto error;
 	if (tx_check_schema(msg->header.schema_version))
 		goto error;
 	assert(msg->header.type == IPROTO_EXECUTE ||
@@ -1825,7 +1894,11 @@ error:
 static void
 tx_process_replication(struct cmsg *m)
 {
-	struct iproto_msg *msg = tx_accept_msg(m);
+	struct iproto_msg *msg;
+	if (tx_accept_msg(m, &msg) != 0) {
+		tx_reply_error(msg);
+		return;
+	}
 	struct iproto_connection *con = msg->connection;
 	struct ev_io io;
 	coio_create(&io, con->input.fd);
@@ -1865,6 +1938,29 @@ tx_process_replication(struct cmsg *m)
 	}
 }
 
+static int
+net_check_connection(struct iproto_msg *msg)
+{
+	if (!msg->close_connection)
+		return 0;
+
+	struct iproto_connection *con = msg->connection;
+	struct obuf *out = msg->wpos.obuf;
+	int64_t nwr = sio_writev(con->output.fd, out->iov,
+				 obuf_iovcnt(out));
+
+	if (nwr > 0) {
+		/* Count statistics. */
+		rmean_collect(rmean_net, IPROTO_SENT, nwr);
+	} else if (nwr < 0 && ! sio_wouldblock(errno)) {
+		diag_log();
+	}
+	assert(iproto_connection_is_idle(con));
+	iproto_connection_close(con);
+	iproto_msg_delete(msg);
+	return -1;
+}
+
 static void
 net_send_msg(struct cmsg *m)
 {
@@ -1881,6 +1977,9 @@ net_send_msg(struct cmsg *m)
 	}
 	con->wend = msg->wpos;
 
+	if (net_check_connection(msg) != 0)
+		return;
+
 	if (evio_has_fd(&con->output)) {
 		if (! ev_is_active(&con->output))
 			ev_feed_event(con->loop, &con->output, EV_WRITE);
@@ -1910,6 +2009,10 @@ net_end_join(struct cmsg *m)
 	struct iproto_connection *con = msg->connection;
 
 	msg->p_ibuf->rpos += msg->len;
+
+	if (net_check_connection(msg) != 0)
+		return;
+
 	iproto_msg_delete(msg);
 
 	assert(! ev_is_active(&con->input));
@@ -1928,6 +2031,10 @@ net_end_subscribe(struct cmsg *m)
 	struct iproto_connection *con = msg->connection;
 
 	msg->p_ibuf->rpos += msg->len;
+
+	if (net_check_connection(msg) != 0)
+		return;
+
 	iproto_msg_delete(msg);
 
 	assert(! ev_is_active(&con->input));
@@ -1936,81 +2043,49 @@ net_end_subscribe(struct cmsg *m)
 }
 
 /**
- * Handshake a connection: invoke the on-connect trigger
- * and possibly authenticate. Try to send the client an error
- * upon a failure.
+ * Handshake a connection: prepare greeting for it.
  */
 static void
-tx_process_connect(struct cmsg *m)
+iproto_process_connect(struct iproto_msg *msg)
 {
-	struct iproto_msg *msg = (struct iproto_msg *) m;
 	struct iproto_connection *con = msg->connection;
 	struct obuf *out = msg->connection->tx.p_obuf;
-	try {              /* connect. */
-		con->session = session_create(SESSION_TYPE_BINARY);
-		if (con->session == NULL)
-			diag_raise();
-		con->session->meta.connection = con;
-		tx_fiber_init(con->session, 0);
-		char *greeting = (char *) static_alloc(IPROTO_GREETING_SIZE);
-		/* TODO: dirty read from tx thread */
-		struct tt_uuid uuid = INSTANCE_UUID;
-		random_bytes(con->salt, IPROTO_SALT_SIZE);
-		greeting_encode(greeting, tarantool_version_id(), &uuid,
-				con->salt, IPROTO_SALT_SIZE);
-		obuf_dup_xc(out, greeting, IPROTO_GREETING_SIZE);
-		if (! rlist_empty(&session_on_connect)) {
-			if (session_run_on_connect_triggers(con->session) != 0)
-				diag_raise();
-		}
-		iproto_wpos_create(&msg->wpos, out);
-	} catch (Exception *e) {
-		tx_reply_error(msg);
-		msg->close_connection = true;
-	}
-}
-
-/**
- * Send a response to connect to the client or close the
- * connection in case on_connect trigger failed.
- */
-static void
-net_send_greeting(struct cmsg *m)
-{
-	struct iproto_msg *msg = (struct iproto_msg *) m;
-	struct iproto_connection *con = msg->connection;
-	if (msg->close_connection) {
-		struct obuf *out = msg->wpos.obuf;
-		int64_t nwr = sio_writev(con->output.fd, out->iov,
-					 obuf_iovcnt(out));
-
-		if (nwr > 0) {
-			/* Count statistics. */
-			rmean_collect(rmean_net, IPROTO_SENT, nwr);
-		} else if (nwr < 0 && ! sio_wouldblock(errno)) {
-			diag_log();
-		}
-		assert(iproto_connection_is_idle(con));
-		iproto_connection_close(con);
-		iproto_msg_delete(msg);
-		return;
-	}
+	char *greeting = (char *) static_alloc(IPROTO_GREETING_SIZE);
+	struct tt_uuid uuid = INSTANCE_UUID;
+	random_bytes(con->salt, IPROTO_SALT_SIZE);
+	greeting_encode(greeting, tarantool_version_id(), &uuid,
+			con->salt, IPROTO_SALT_SIZE);
+	obuf_dup_xc(out, greeting, IPROTO_GREETING_SIZE);
+	iproto_wpos_create(&msg->wpos, out);
 	con->wend = msg->wpos;
-	/*
-	 * Connect is synchronous, so no one could have been
-	 * messing up with the connection while it was in
-	 * progress.
-	 */
 	assert(evio_has_fd(&con->output));
-	/* Handshake OK, start reading input. */
 	ev_feed_event(con->loop, &con->output, EV_WRITE);
 	iproto_msg_delete(msg);
 }
 
-static const struct cmsg_hop connect_route[] = {
-	{ tx_process_connect, &net_pipe },
-	{ net_send_greeting, NULL },
-};
+static int
+tx_init_connect(struct iproto_msg *msg)
+{
+	struct iproto_connection *con = msg->connection;
+	obuf_create(&con->obuf[0], &net_slabc, iproto_readahead);
+	obuf_create(&con->obuf[1], &net_slabc, iproto_readahead);
+	con->tx.p_obuf = &con->obuf[0];
+	iproto_wpos_create(&con->wpos, con->tx.p_obuf);
+	iproto_wpos_create(&con->wend, con->tx.p_obuf);
+
+	con->session = session_create(SESSION_TYPE_BINARY);
+	if (con->session == NULL)
+		return -1;
+	con->session->meta.connection = con;
+
+	tx_fiber_init(con->session, 0);
+	if (! rlist_empty(&session_on_connect)) {
+		if (session_run_on_connect_triggers(con->session) != 0)
+			return -1;
+	}
+
+	return 0;
+}
 
 /** }}} */
 
@@ -2037,11 +2112,10 @@ iproto_on_accept(struct evio_service * /* service */, int fd,
 		mempool_free(&iproto_connection_pool, con);
 		return -1;
 	}
-	cmsg_init(&msg->base, connect_route);
 	msg->p_ibuf = con->p_ibuf;
 	msg->wpos = con->wpos;
 	msg->close_connection = false;
-	cpipe_push(&tx_pipe, &msg->base);
+	iproto_process_connect(msg);
 	return 0;
 }
 
@@ -2054,6 +2128,8 @@ static struct evio_service binary; /* iproto binary listener */
 static int
 net_cord_f(va_list /* ap */)
 {
+	slab_cache_create(&iproto_slabc, &runtime);
+
 	mempool_create(&iproto_msg_pool, &cord()->slabc,
 		       sizeof(struct iproto_msg));
 	mempool_create(&iproto_connection_pool, &cord()->slabc,
@@ -2297,7 +2373,8 @@ iproto_listen(const char *uri)
 size_t
 iproto_mem_used(void)
 {
-	return slab_cache_used(&net_cord.slabc) + slab_cache_used(&net_slabc);
+	return slab_cache_used(&net_cord.slabc)
+	     + slab_cache_used(&net_slabc) + slab_cache_used(&iproto_slabc);
 }
 
 size_t
diff --git a/test/box-py/bad_trigger.result b/test/box-py/bad_trigger.result
index 5d064b7648..bfa9c2b759 100644
--- a/test/box-py/bad_trigger.result
+++ b/test/box-py/bad_trigger.result
@@ -14,6 +14,7 @@ type(box.session.on_connect(f1))
 - function
 ...
 greeting:  True
+Nothing to read yet:  Resource temporarily unavailable
 fixheader:  True
 error code 32
 error message:  [string "function f1() nosuchfunction() end"]:1: attempt to call global 'nosuchfunction' (a nil value)
diff --git a/test/box-py/bad_trigger.test.py b/test/box-py/bad_trigger.test.py
index 7d200b9218..7f45f5e713 100644
--- a/test/box-py/bad_trigger.test.py
+++ b/test/box-py/bad_trigger.test.py
@@ -2,7 +2,7 @@ from lib.box_connection import BoxConnection
 from lib.tarantool_connection import TarantoolConnection
 from tarantool import NetworkError
 from tarantool.const import IPROTO_GREETING_SIZE, IPROTO_CODE, IPROTO_ERROR, \
-    REQUEST_TYPE_ERROR
+    REQUEST_TYPE_ERROR, REQUEST_TYPE_PING
 import socket
 import msgpack
 
@@ -26,9 +26,25 @@ s = conn.socket
 # Read greeting
 print 'greeting: ', len(s.recv(IPROTO_GREETING_SIZE)) == IPROTO_GREETING_SIZE
 
-# Read error packet
+# Check soscket
 IPROTO_FIXHEADER_SIZE = 5
-fixheader = s.recv(IPROTO_FIXHEADER_SIZE)
+s.setblocking(False)
+fixheader = None
+try:
+    fixheader = s.recv(IPROTO_FIXHEADER_SIZE)
+except socket.error as err:
+    print 'Nothing to read yet:', str(err).split(']')[1]
+else:
+    print 'Received fixheader'
+s.setblocking(True)
+
+# Send ping
+query = msgpack.dumps({ IPROTO_CODE : REQUEST_TYPE_PING })
+s.send(msgpack.dumps(len(query)) + query)
+
+# Read error packet
+if not fixheader:
+    fixheader = s.recv(IPROTO_FIXHEADER_SIZE)
 print 'fixheader: ', len(fixheader) == IPROTO_FIXHEADER_SIZE
 unpacker.feed(fixheader)
 packet_len = unpacker.unpack()
-- 
2.17.1