Add test checking binlog reader uses previous hostgroup

When a COM_REGISTER_SLAVE command is received, test that ProxySQL will
automatically switch from not fast_forward mode to fast_forward mode.
It also test that the destination hostgroup assigned from previous
COM_QUERY commands is the one used to establish the fast_forward
connection. To test this we look at how many connections are closed in
the hostgroup that should have been used for the fast_forward
connections.

test/tap/tests/test_binlog_reader_uses_previous_hostgroup-t.cpp

@@ -0,0 +1,140 @@
+/**
+ * @file test_binlog_reader_uses_previous_hostgroup-t.cpp
+ * @brief Test binlog reader uses the hostgroup of the previous COM_QUERY.
+ * @details When a COM_REGISTER_SLAVE command is received, test that ProxySQL
+ * will automatically switch from not fast_forward mode to fast_forward mode.
+ * It also test that the destination hostgroup assigned from previous COM_QUERY
+ * commands is the one used to establish the fast_forward connection. To test
+ * this we look at how many connections are closed in the hostgroup that should
+ * have been used for the fast_forward connections.
+ */
+
+#include <unistd.h>
+#include <mysql.h>
+#include <vector>
+#include <string>
+
+#include "proxysql_utils.h"
+#include "command_line.h"
+#include "utils.h"
+#include "tap.h"
+
+using std::vector;
+using std::string;
+
+const char* QUERY_CONN_CLOSED {
+	"SELECT ConnOk - ConnFree FROM stats.stats_mysql_connection_pool WHERE hostgroup=%d"
+};
+
+int conn_pool_hg_stat_conn_closed(MYSQL* proxy_admin, int hg_id, vector<string>& out_stats) {
+	MYSQL_RES* my_stats_res = NULL;
+
+	string conn_pool_query {};
+	string_format(QUERY_CONN_CLOSED, conn_pool_query, hg_id);
+
+	int err = mysql_query(proxy_admin, conn_pool_query.c_str());
+	if (err) {
+		diag("Failed to executed query `%s`", conn_pool_query.c_str());
+		err = EXIT_FAILURE;
+		goto cleanup;
+	}
+
+	{
+		my_stats_res = mysql_store_result(proxy_admin);
+
+		vector<vector<string>> my_rows { extract_mysql_rows(my_stats_res) };
+		if (my_rows.size() != 1) {
+			diag("Failed condition; test expects only 1");
+			err = EXIT_FAILURE;
+			goto cleanup;
+		}
+
+		// Return the unique expected row as result
+		out_stats = my_rows.front();
+	}
+
+cleanup:
+
+	mysql_free_result(my_stats_res);
+
+	return err;
+}
+
+int main(int argc, char** argv) {
+	CommandLine cl;
+
+	if (cl.getEnv()) {
+		diag("Failed to get the required environmental variables.");
+		return EXIT_FAILURE;
+	}
+
+	MYSQL* proxy_admin = mysql_init(NULL);
+	if (!mysql_real_connect(proxy_admin, cl.host, cl.admin_username, cl.admin_password, NULL, cl.admin_port, NULL, 0)) {
+		fprintf(stderr, "File %s, line %d, Error: %s\n", __FILE__, __LINE__, mysql_error(proxy_admin));
+		return EXIT_FAILURE;
+	}
+
+	const int destination_hostgroup = 2;
+	string query;
+	query = "DELETE FROM mysql_servers WHERE hostgroup_id=" + std::to_string(destination_hostgroup);
+	diag("Running: %s", query.c_str());
+	MYSQL_QUERY(proxy_admin, query.c_str());
+	query = "INSERT INTO mysql_servers (hostgroup_id, hostname, port, use_ssl) "
+			"VALUES (" + std::to_string(destination_hostgroup) + ", '127.0.0.1', 13306, 0)";
+	diag("Running: %s", query.c_str());
+	MYSQL_QUERY(proxy_admin, query.c_str());
+	query = "LOAD MYSQL SERVERS TO RUNTIME";
+	diag("Running: %s", query.c_str());
+	MYSQL_QUERY(proxy_admin, query.c_str());
+	query = "DELETE FROM mysql_query_rules";
+	diag("Running: %s", query.c_str());
+	MYSQL_QUERY(proxy_admin, query.c_str());
+	query = "INSERT INTO mysql_query_rules (rule_id, active, proxy_port, destination_hostgroup, log) "
+			"VALUES (1, 1, " + std::to_string(cl.port) + ", " + std::to_string(destination_hostgroup) + ", 1)";
+	diag("Running: %s", query.c_str());
+	MYSQL_QUERY(proxy_admin, query.c_str());
+	query = "LOAD MYSQL QUERY RULES TO RUNTIME";
+	diag("Running: %s", query.c_str());
+	MYSQL_QUERY(proxy_admin, query.c_str());
+
+	vector<string> hg_stats_row {};
+	int my_err = conn_pool_hg_stat_conn_closed(proxy_admin, destination_hostgroup, hg_stats_row);
+	if (my_err) {
+		mysql_close(proxy_admin);
+		return EXIT_FAILURE;
+	}
+	const long conn_closed_before = std::stol(hg_stats_row[0]);
+
+	const std::string test_deps_path = getenv("TEST_DEPS");
+	const int test_binlog_reader_res = system((test_deps_path + "/test_binlog_reader-t").c_str());
+	if (test_binlog_reader_res) {
+		mysql_close(proxy_admin);
+		return EXIT_FAILURE;
+	}
+
+	int wait_res = wait_for_backend_conns(proxy_admin, "ConnUsed", 0, 5);
+	if (wait_res != EXIT_SUCCESS) {
+		diag("Error waiting for ProxySQL to close backend connection.");
+		return EXIT_FAILURE;
+	}
+
+	my_err = conn_pool_hg_stat_conn_closed(proxy_admin, destination_hostgroup, hg_stats_row);
+	if (my_err) {
+		mysql_close(proxy_admin);
+		return EXIT_FAILURE;
+	}
+	const long conn_closed_after = std::stol(hg_stats_row[0]);
+
+	// test_binlog_reader-t tool make two fast_forward connections, so we
+	// should expect two more closed connections after its execution.
+	const int expected_increment = 2;
+	ok(
+		(conn_closed_after - conn_closed_before) == expected_increment,
+		// Connections used for fast_forward are closed once the client disconnects.
+		"Two connections should have been closed."
+			" Connections closed - Exp:'%d', Act:'%ld'",
+		expected_increment, conn_closed_after - conn_closed_before
+	);
+
+	return exit_status();
+}