High CPU usage in Mysql

Mysql causes high CPU usage. The server environment Liunx AS4 + PHP5 + Mysql5 + Apache 2

When I used the TOP command to query the system performance, I found that the CPU often reached 100% and started to think it was a DDOS attack ...... After a firewall is installed (does not work), you can start from the liunx system to find out if it is a system problem (or does not work ).

I occasionally found an article on the Internet, and someone encountered such a problem, but did not point out the specific solution, but reminded me that it was either a system problem or a program problem! This time, I began to filter PHP code again. Occasionally, I found that many of my brother's code is only a "regular" connection, and I didn't Close it! I installed a database to close all the pages, and found that the CPU has been maintained at 1% ~ Between 10% (normal), so remind everyone not to be a little lazy when writing PHP programs, resulting in system overflow such a low-level error! Let's write it down here. I spent almost one afternoon on a small problem! It's also a lesson!

Remember to paste some common mysql functions! Other types of databases are similar!

Mysql_affected_rows -- gets the number of records affected by the previous MySQL operation

Mysql_change_user -- change the user logged on to the active connection

Mysql_client_encoding -- returns the name of the character set.

Mysql_close -- close the MySQL connection

Mysql_connect -- open a connection to the MySQL server

Mysql_create_db -- create a MySQL database

Mysql_data_seek -- move the internal result pointer

Mysql_db_name -- get result data

Mysql_db_query -- send a MySQL Query

Mysql_drop_db -- discard (delete) a MySQL database

Mysql_errno -- returns the numeric encoding of the error message in the previous MySQL operation

Mysql_error -- returns the text error message generated by the previous MySQL operation.

Mysql_escape_string -- escape a string for mysql_query

Mysql_fetch_array -- get a row from the result set as an associated array, or a number array, or both

Mysql_fetch_assoc -- get a row from the result set as the associated array

Mysql_fetch_field -- obtains column information from the result set and returns it as an object

Mysql_fetch_lengths -- get the length of each output in the result set

Mysql_fetch_object -- get a row from the result set as an object

Mysql_fetch_row -- obtains a row from the result set as an enumerated Array

Mysql_field_flags -- obtains the flag associated with the specified field from the result

Mysql_field_len -- returns the length of the specified field

Mysql_field_name -- obtains the field name of the specified field in the result.

Mysql_field_seek -- set the pointer in the result set to the specified field offset.

Mysql_field_table -- get the name of the table where the specified field is located

Mysql_field_type -- specify the field type in the result set

Mysql_free_result -- release result memory

Mysql_get_client_info -- Obtain MySQL client information

Mysql_get_host_info -- Obtain MySQL host information

Mysql_get_proto_info -- Obtain MySQL protocol information

Mysql_get_server_info -- Obtain MySQL Server Information

Mysql_info -- get the information of the last Query

Mysql_insert_id -- get the ID generated by the previous INSERT operation

Mysql_list_dbs -- list all databases on the MySQL server

Mysql_list_fields -- list fields in MySQL results

Mysql_list_processes -- list MySQL Processes

Mysql_list_tables -- list tables in the MySQL database

Mysql_num_fields -- obtain the number of fields in the result set.

Mysql_num_rows -- get the number of rows in the result set

Mysql_pconnect -- open a persistent connection to the MySQL server

Mysql_ping -- Ping a server connection. If there is no connection, reconnect.

Mysql_query -- send a MySQL Query

Mysql_real_escape_string -- escape special characters in strings used in SQL statements and take into account the connected Current Character Set

Mysql_result -- get result data

Mysql_select_db -- select MySQL database

Mysql_stat -- get the current system status

Mysql_tablename -- get the table name

Mysql_thread_id -- returns the ID of the current thread

Mysql_unbuffered_query -- a row that sends an SQL query to MySQL and does not obtain or cache the result.