Too many connections to mysql

1. Error: "Too many connections"  --> SET GLOBAL max_connections = 1000;
read more in :
- https://dev.mysql.com/doc/refman/5.5/en/server-system-variables.html#sysvar_max_connections
- http://kedar.nitty-witty.com/blog/calculte-mysql-memory-usage-quick-stored-proc
- http://dev.mysql.com/doc/refman/5.5/en/memory-use.html
- http://stackoverflow.com/questions/1178736/mysql-maximum-memory-usage

To get Maximum Memory that Mysql need:
SHOW VARIABLES LIKE 'innodb_buffer_pool_size';
SHOW VARIABLES LIKE 'innodb_additional_mem_pool_size';
SHOW VARIABLES LIKE 'innodb_log_buffer_size';
SHOW VARIABLES LIKE 'thread_stack';
SET @kilo_bytes = 1024;
SET @mega_bytes = @kilo_bytes * 1024;
SET @giga_bytes = @mega_bytes * 1024;
SET @innodb_buffer_pool_size = 2 * @giga_bytes;
SET @innodb_additional_mem_pool_size = 16 * @mega_bytes;
SET @innodb_log_buffer_size = 8 * @mega_bytes;
SET @thread_stack = 192 * @kilo_bytes;
SELECT
( @@key_buffer_size + @@query_cache_size + @@tmp_table_size
+ @innodb_buffer_pool_size + @innodb_additional_mem_pool_size
+ @innodb_log_buffer_size
+ @@max_connections * (
@@read_buffer_size + @@read_rnd_buffer_size + @@sort_buffer_size
+ @@join_buffer_size + @@binlog_cache_size + @thread_stack
) ) / @giga_bytes AS MAX_MEMORY_GB;