CONC-365: Failover capabilities

host parameter of mysql_real_connect (and corresponding configuration
settings MYSQL_OPT_HOST for mysql_options() api call and host key in
configuration files) now accepts to specify multiple hosts and ports.

When establishing a connection, the list of specified hosts is run
through until a connection can be established. If no connection
can be established to any of the specified hosts, an error is returned.

Specifications for multiple hosts/ports:

- hostname and port must be seperated by a colon (:)
- IPv6 addresses must be enclosed within square brackets
- hostname:port pairs must be be seperated by a comma (,)
- if only one host:port was specified, the host string needs to end
  with a comma.
- if no port was specified, the default port will be used.

Examples for failover host string:

host=[::1]:3306,192.168.0.1:3306,test.example.com
host=localhost:3306,

libmariadb/mariadb_lib.c

@@ -1485,6 +1485,44 @@ mysql_real_connect(MYSQL *mysql, const char *host, const char *user,
 #endif
 }
 
+struct st_host {
+  char *host;
+  int port;
+};
+
+static void ma_get_host_list(char *host_list, struct st_host *host_info, int default_port)
+{
+  char *token, *start, *save;
+  int host_nr= 0;
+
+  start= host_list;
+  while ((token= strtok_r(start, ",", &save)))
+  {
+    char *p;
+
+    /* ipv6 hostname */
+    if ((p= strchr(token, ']')))
+    {
+      host_info[host_nr].host= token + 1;
+      *p++= 0;
+      token= p;
+    }
+    else
+      host_info[host_nr].host= token;
+    /* check if port was specified */
+    if ((p= strchr(token, ':')))
+    {
+      *p++= 0;
+      host_info[host_nr].port= atoi(p);
+    }
+    else
+      host_info[host_nr].port= default_port;
+    host_nr++;
+    start= NULL;
+  }
+  return;
+}
+
 MYSQL *mthd_my_real_connect(MYSQL *mysql, const char *host, const char *user,
 		   const char *passwd, const char *db,
 		   uint port, const char *unix_socket, unsigned long client_flag)
@@ -1498,6 +1536,10 @@ MYSQL *mthd_my_real_connect(MYSQL *mysql, const char *host, const char *user,
   const char *scramble_plugin;
   uint pkt_length, scramble_len, pkt_scramble_len= 0;
   NET	*net= &mysql->net;
+  my_bool is_multi= 0;
+  char *host_copy= NULL;
+  struct st_host *host_list= NULL;
+  int connect_attempts= 0;
 
   if (!mysql->methods)
     mysql->methods= &MARIADB_DEFAULT_METHODS;
@@ -1520,6 +1562,54 @@ MYSQL *mthd_my_real_connect(MYSQL *mysql, const char *host, const char *user,
     mysql->options.my_cnf_file=mysql->options.my_cnf_group=0;
   }
 
+  if (!port)
+    port=mysql->options.port;
+  if (!host || !host[0])
+    host= mysql->options.host;
+
+  /* check if we have multi hosts */
+  if (host && host[0] && strchr(host, ','))
+  {
+    char *p;
+    size_t host_count= 1;
+
+    is_multi= 1;
+
+    /* don't change original entry, so let's make a copy */
+    if (!(host_copy= strdup(host)))
+    {
+      SET_CLIENT_ERROR(mysql, CR_OUT_OF_MEMORY, SQLSTATE_UNKNOWN, 0);
+      goto error;
+    }
+
+    p= host_copy;
+
+    while ((p = strchr(p, ',')))
+    {
+      host_count++;
+      p++;
+    }
+
+    if (!(host_list= (struct st_host *)calloc(host_count + 1, sizeof(struct st_host))))
+    {
+      SET_CLIENT_ERROR(mysql, CR_OUT_OF_MEMORY, SQLSTATE_UNKNOWN, 0);
+      goto error;
+    }
+
+    ma_get_host_list(host_copy, host_list, port);
+  }
+
+restart:
+  /* check if we reached end of list */
+  if (is_multi)
+  {
+    if (!host_list[connect_attempts].host)
+      goto error;
+
+    host= host_list[connect_attempts].host;
+    port= host_list[connect_attempts].port;
+  }
+
   ma_set_connect_attrs(mysql, host);
 
 #ifndef WIN32
@@ -1545,8 +1635,6 @@ MYSQL *mthd_my_real_connect(MYSQL *mysql, const char *host, const char *user,
   }
   if (!db || !db[0])
     db=mysql->options.db;
-  if (!port)
-    port=mysql->options.port;
   if (!unix_socket)
     unix_socket=mysql->options.unix_socket;
 
@@ -1609,6 +1697,11 @@ MYSQL *mthd_my_real_connect(MYSQL *mysql, const char *host, const char *user,
   if (ma_pvio_connect(pvio, &cinfo) != 0)
   {
     ma_pvio_close(pvio);
+    if (is_multi)
+    {
+      connect_attempts++;
+      goto restart;
+    }
     goto error;
   }
 
@@ -1846,10 +1939,16 @@ MYSQL *mthd_my_real_connect(MYSQL *mysql, const char *host, const char *user,
   /* connection established, apply timeouts */
   ma_pvio_set_timeout(mysql->net.pvio, PVIO_READ_TIMEOUT, mysql->options.read_timeout);
   ma_pvio_set_timeout(mysql->net.pvio, PVIO_WRITE_TIMEOUT, mysql->options.write_timeout);
+
+  free(host_list);
+  free(host_copy);
+
   return(mysql);
 
 error:
   /* Free allocated memory */
+  free(host_list);
+  free(host_copy);
   end_server(mysql);
   /* only free the allocated memory, user needs to call mysql_close */
   mysql_close_memory(mysql);

unittest/libmariadb/connection.c

@@ -1999,8 +1999,6 @@ static int test_conn_str(MYSQL *my __attribute__((unused)))
     strcat(conn_str, ";ssl_enforce=1");
   }
 
-  diag("connection string: %s", conn_str);
-  
   if (mariadb_connect(mysql, conn_str))
   {
     diag("host: %s", mysql->host);
@@ -2025,7 +2023,9 @@ static int test_conn_str_1(MYSQL *my __attribute__((unused)))
     return FAIL;
 
   fprintf(fp, "[client]\n");
-  fprintf(fp, "connection=host=%s;user=%s;password=%s;port=%d;ssl_enforce=1\n", hostname, username, password, port);
+  fprintf(fp, "connection=host=%s;user=%s;password=%s;port=%d;ssl_enforce=1\n",
+                hostname ? hostname : "localhost", username ? username : "", 
+                password ? password : "", port);
 
   fclose(fp);
 
@@ -2052,7 +2052,95 @@ static int test_conn_str_1(MYSQL *my __attribute__((unused)))
   return OK;
 }
 
+static int test_conc365(MYSQL *my __attribute__((unused)))
+{
+  int rc= OK;
+  MYSQL *mysql= mysql_init(NULL);
+  char tmp[1024];
+
+  snprintf(tmp, sizeof(tmp) - 1,
+   "host=127.0.0.1:3300,%s;user=%s;password=%s;port=%d",
+   hostname ? hostname : "localhost", username ? username : "", password ? password : "",
+   port);
+
+ if (IS_SKYSQL(hostname))
+   strcat(tmp, ";ssl_enforce=1");
+
+ if (!mariadb_connect(mysql, tmp))
+   rc= FAIL;
+
+  mysql_close(mysql);
+
+  if (rc)
+    return rc;
+
+  mysql= mysql_init(NULL);
+  snprintf(tmp, sizeof(tmp) -1, "127.0.0.1:3300,%s:%d", hostname ? hostname : "localhost", port);
+  if (!my_test_connect(mysql, tmp, username,
+                             password, schema, port, socketname, 0))
+  {
+    diag("Error: %s", mysql_error(mysql));
+    rc= FAIL;
+  }
+
+  mysql_close(mysql);
+
+  if (rc)
+    return rc;
+  
+  mysql= mysql_init(NULL);
+  mysql_options(mysql, MARIADB_OPT_HOST, tmp);
+  if (!my_test_connect(mysql, NULL, username,
+                             password, schema, port, socketname, 0))
+  {
+    diag("Error: %s", mysql_error(mysql));
+    rc= FAIL;
+  }
+
+  mysql_close(mysql);
+  return rc;
+}
+
+static int test_conc365_reconnect(MYSQL *my)
+{
+  int rc= OK;
+  MYSQL *mysql= mysql_init(NULL);
+  char tmp[1024];
+  my_bool reconnect= 1;
+
+  mysql_options(mysql, MYSQL_OPT_RECONNECT, &reconnect);
+
+  snprintf(tmp, sizeof(tmp) - 1,
+   "host=127.0.0.1:3300,%s;user=%s;password=%s;port=%d",
+   hostname ? hostname : "localhost", username ? username : "", password ? password : "",
+   port);
+
+ if (IS_SKYSQL(hostname))
+   strcat(tmp, ";ssl_enforce=1");
+
+  if (!my_test_connect(mysql, tmp, username,
+                             password, schema, port, socketname, CLIENT_REMEMBER_OPTIONS))
+  {
+    diag("Error: %s", mysql_error(mysql));
+    rc= FAIL;
+  }
+
+  sprintf(tmp, "KILL %ld", mysql_thread_id(mysql));
+
+  rc= mysql_query(my, tmp);
+  check_mysql_rc(rc, my);
+
+  sleep(3);
+  rc= mysql_ping(mysql);
+  check_mysql_rc(rc, my);
+
+  mysql_close(mysql);
+  return rc;
+}
+
 struct my_tests_st my_tests[] = {
+  {"test_conc365", test_conc365, TEST_CONNECTION_NONE, 0, NULL, NULL},
+  {"test_conc365_reconnect", test_conc365_reconnect, TEST_CONNECTION_DEFAULT, 0, NULL, NULL},
   {"test_conn_str", test_conn_str, TEST_CONNECTION_NONE, 0, NULL, NULL},
   {"test_conn_str_1", test_conn_str_1, TEST_CONNECTION_NONE, 0, NULL, NULL},
   {"test_conc544", test_conc544, TEST_CONNECTION_DEFAULT, 0, NULL, NULL},