… max_packet_size per connection) are all connection buffers and so if you close connection MySQL can clean them up. Killing connections (or stopping related… take on server. There is no comparable variables of how many user variables are allocated (and how much memory they use… away if you close connection. In Percona Server you can do better as you can query temporary tables too: mysql> select sum(data…
Post: How FLUSH TABLES WITH READ LOCK works with Innodb Tables
March 23, 2012 By 20 Comments
… be blocked too, which among other tools used by mysql client, so you might get a feel you can’t connect to the database at all (use mysql -A in…) you can consider using –no-lock option with Percona Xtrabackup. Many other tools have similar option. This option can be especially…
Post: Too many connections? No problem!
March 23, 2010 By 28 Comments
…5_0_87]$ ./use ERROR 1040 (00000): Too many connections Just happened to one of our… input statement. mysql [localhost] {msandbox} ((none)) > select @@global.max_connections; +————————–+ | @@global.max_connections | +————————–+ | 5000 | +————————–+ 1…
Post: How to Monitor MySQL with Percona's Nagios Plugins
February 22, 2012 By 8 Comments
… will alert when a snapshot is failed or overly full. Too many deadlocks. Deadlocks (and lock wait timeouts, covered in another plugin… error appropriately. The pmp-check-mysql-status plugin can be configured to alert when Threads_connected approaches max_connections too closely, which can give…
Post: MySQL Limitations Part 4: One thread per connection
October 27, 2010 By 14 Comments
… about the way MySQL handles connections, allocating one thread per connection to the server. MySQL is a single…you, Java). And many others use persistent connections by default, so that a connection isn’t really…’t be a great OLTP web database too. MySQL replication is one of the core, fundamental …
Post: What to tune in MySQL Server after installation
September 29, 2006 By 116 Comments
… for people to work as MySQL DBAs or be involved with MySQL Performance in some way … This one does not really affect performance too much, at least on OS with decent memory…hundreds tables (remember each connection needs its own entry) if you have many connections or many tables increase it larger…
Post: Are PHP persistent connections evil ?
November 12, 2006 By 31 Comments
… limit but creating connections will still waste resources and add latency. The other problem with persistent connections is using too many MySQL server connections. Some people simply do not realize you can increase max_connections variable and get over 100 concurrent connections with MySQL…
Post: How Percona diagnoses MySQL server stalls
March 3, 2011 By 6 Comments
… is the thing to check for. VARIABLE=${VARIABLE:-Threads_connected} You need to change the threshold to 15,…do work, and sometimes the problem is doing too much work without blocking. Likewise, it gathers lots… not aware of. There are many things that can cause a stall in MySQL, and they usually begin…
Post: How to debug long-running transactions in MySQL
March 8, 2011 By 6 Comments
… this many MB free. MB_THRESHOLD=100 # Make sure the disk isn’t getting too full. avail… port ${port} > /root/tcpdumps/`date +%s`-tcpdump & mysql -e ‘show innodb status\Gshow full processlist’ > /root/…watch your server to find idle-in-transaction connections that are just sitting there doing nothing,…
Post: MySQL Connection Timeouts
April 19, 2011 By 2 Comments
… busy MySQL server you will see sporadic connection timeouts, such as Can’t connect to MySQL server on ‘mydb’ (110). If you have connects timed… too low for many conditions. Now lets look more into the problem and do some Math. First lets look into how MySQL accepts connection. There is single main thread which is accepting connections coming to LISTEN sockets. Once there is connection coming it…
