Posts Tagged ‘port 3306’

‘host-name’ is blocked because of many connection errors; unblock with ‘mysqladmin flush-hosts’

Sunday, May 20th, 2012

Reading Time: 3minutes

mysql-logo-host-name-blocked-because-of-many-connection-errors
My home run machine MySQL server was suddenly down as I tried to check my blog and other sites today, the error I saw while trying to open, this blog as well as other hosted sites using the MySQL was:

Error establishing a database connection

The topology, where this error occured is simple, I have two hosts:

1. Apache version 2.0.64 compiled support externally PHP scripts interpretation via libphp – the host runs on (FreeBSD)

2. A Debian GNU / Linux squeeze running MySQL server version 5.1.61

The Apache host is assigned a local IP address 192.168.0.1 and the SQL server is running on a host with IP 192.168.0.2

To diagnose the error I've logged in to 192.168.0.2 and weirdly the mysql-server was appearing to run just fine:
 

debian:~# ps ax |grep -i mysql
31781 pts/0 S 0:00 /bin/sh /usr/bin/mysqld_safe
31940 pts/0 Sl 12:08 /usr/sbin/mysqld –basedir=/usr –datadir=/var/lib/mysql –user=mysql –pid-file=/var/run/mysqld/mysqld.pid –socket=/var/run/mysqld/mysqld.sock –port=3306
31941 pts/0 S 0:00 logger -t mysqld -p daemon.error
32292 pts/0 S+ 0:00 grep -i mysql

Moreover I could connect to the localhost SQL server with mysql -u root -p and it seemed to run fine. The error Error establishing a database connection meant that either something is messed up with the database or 192.168.0.2 Mysql port 3306 is not properly accessible.

My first guess was something is wrong due to some firewall rules, so I tried to connect from 192.168.0.1 to 192.168.0.2 with telnet:
 

freebsd# telnet 192.168.0.2 3306
Trying 192.168.0.2…
Connected to jericho.
Escape character is '^]'.
Host 'webserver' is blocked because of many connection errors; unblock with 'mysqladmin flush-hosts'
Connection closed by foreign host.

Right after the telnet was initiated as I show in the above output the connection was immediately closed with the error:

Host 'webserver' is blocked because of many connection errors; unblock with 'mysqladmin flush-hosts'Connection closed by foreign host.

In the error 'webserver' is my Apache machine set hostname. The error clearly states the problems with the 'webserver' apache host unable to connect to the SQL database are due to 'many connection errors' and a fix i suggested with mysqladmin flush-hosts

To temporary solve the error and restore my normal connectivity between the Apache and the SQL servers I logged I had to issue on the SQL host:

mysqladmin -u root -p flush-hostsEnter password:

Thogh this temporar fix restored accessibility to the databases and hence the websites errors were resolved, this doesn't guarantee that in the future I wouldn't end up in the same situation and therefore I looked for a permanent fix to the issues once and for all.

The permanent fix consists in changing the default value set for max_connect_error in /etc/mysql/my.cnf, which by default is not too high. Therefore to raise up the variable value, added in my.cnf in conf section [mysqld]:

debian:~# vim /etc/mysql/my.cnf
...
max_connect_errors=4294967295

and afterwards restarted MYSQL:

debian:~# /etc/init.d/mysql restart
Stopping MySQL database server: mysqld.
Starting MySQL database server: mysqld.
Checking for corrupt, not cleanly closed and upgrade needing tables..

To make sure the assigned max_connect_errors=4294967295 is never reached due to Apache to SQL connection errors, I've also added as a cronjob.

debian:~# crontab -u root -e
00 03 * * * mysqladmin flush-hosts

In the cron I have omitted the mysqladmin -u root -p (user/pass) input options because for convenience I have already stored the mysql root password in /root/.my.cnf

Here is how /root/.my.cnf looks like:

debian:~# cat /root/.my.cnf
[client]
user=root
password=a_secret_sql_password

Now hopefully, this would permanently solve SQL's 'failure to accept connections' due to too many connection errors for future.

How to fix “ERROR 1577 (HY000) at line 1: Cannot proceed because system tables used by Event Scheduler were found damaged at server start”

Saturday, May 12th, 2012

Reading Time: 3minutes

After migrating databases data from FreeBSD MySQL 5.0.83 server to a Debian Squeeze Linux MySQL version 5.1.61, below is a mysql –version issued on both the FreeBSD and the Debian servers

freebsd# mysql --version
mysql Ver 14.12 Distrib 5.0.83, for portbld-freebsd7.2 (i386) using 5.2

debian:~# mysql --version
mysql Ver 14.14 Distrib 5.1.61, for debian-linux-gnu (i486) using readline 6.1

The data SQL dump from the FreeBSD server was dumped with following command arguments:

freebsd# mysqldump --opt --allow-keywords --add-drop-table --all-databases -u root -p > complete_db_dump.sql

Then I used sftp to transfer complete_db_dump.sql dump to the a brand new installed latest Debian Squeeze 6.0.2. The Debian server was installed using a "clean Debian install" without graphical environment with CD downloaded from debian.org's site.

On the Debian machine I imported the dump with command:

debian:~# mysq -u root -p < complete_db_dump.sql

Right After the dump was imported I re-started SQL server which was previously installed with:

debian:~# apt-get install mysql-server
The error I got after restarting the mysql server:

debian:~# #/etc/init.d/mysql restart

was:

ERROR 1577 (HY000) at line 1: Cannot proceed because system tables used by Event Scheduler were found damaged at server start
ERROR 1547 (HY000) at line 1: Column count of mysql.proc is wrong. Expected 20, found 16. The table is probably corrupted

This error cost me a lot of nerves and searching in google to solve. It took me like half an hour of serious googling ,until I finally found the FIX!!!:

debian:~# mysql_upgrade -u root -h localhost -p --verbose --force
Enter password:
Looking for 'mysql' as: mysql
Looking for 'mysqlcheck' as: mysqlcheck
Running 'mysqlcheck' with connection arguments: '--port=3306' '--socket=/var/run/mysqld/mysqld.sock' '--host=localhost'
Running 'mysqlcheck' with connection arguments: '--port=3306' '--socket=/var/run/mysqld/mysqld.sock' '--host=localhost'
bible.holy_bible OK
bible.holybible OK
bible.quotes_meta OK

Afterwards finally I had to restart the mysql server once again in order to finally get rid of the shitty:

ERROR 1547 (HY000) at line 1: Column count of mysql.proc is wrong. Expected 20, found 16. The table is probably corrupted error!

debian:~# /etc/init.d/mysql restart
Stopping MySQL database server: mysqld.
Starting MySQL database server: mysqld.
Checking for corrupt, not cleanly closed and upgrade needing tables..

This solved the insane Column count of mysql.proc is wrong. Expected 20, found 16 once and for all!

Before I came with this fix I tried all kind of forum suggested fixes like:

debian:~# mysql_upgrade -u root -p
Looking for 'mysql' as: mysql
Looking for 'mysqlcheck' as: mysqlcheck
This installation of MySQL is already upgraded to 5.1.61, use --force if you still need to run mysql_upgrade

debian:~# mysql_upgrade -p
Looking for 'mysql' as: mysql
Looking for 'mysqlcheck' as: mysqlcheck
This installation of MySQL is already upgraded to 5.1.61, use --force if you still need to run mysql_upgrade

And few more, none of them worked the only one that worked was:

debian:~# #mysql_upgrade -u root -h localhost -p --verbose --force

I have to say big thanks to Mats Lindth wonderful blog post which provided me with the solution.

It seems, since Oracle bought the Community edition of MySQL thinks with this database server are getting more and more messy and backwards incompatible day by day.
Lately, I'm experiencing too much hassles with MySQL version incompitabilities. Maybe I should think for migrating permanently to Postgre …

By the way the ERROR 1547 (HY000) at line 1: Column count of mysql.proc is wrong. is most probably caused of some kind of password hashing incompitability between the password hashing between the BSD and Debian SQL versions, as mysql -u root -p < dump.sql, does override default stored user passwords in the mysql database tables… Such password, hashing issues were common in prior MySQL 4 to MySQL 5 migrations I've done, however since MySQL 5+ is already storing its password strings encrypted with md5 encryption I wonder why on earth this mess happens ….