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# Month: August 2015

## Percona Live Amsterdam: Community Dinner, Sep. 22nd

MySQL community PerconaLive August 13, 2015

Keeping up with tradition, there will be a community event held at the upcoming Percona Live Europe: Amsterdam 2015 conference.

This year, Booking.com will be hosting the event at the company’s headquarters in the heart of Amsterdam.

We will hold a community dinner (dish selection, includes vegetarian; beverages will be served) in our caffeteria and hope to add some spicy activities to the event!

Space is limited, and tickets can be purchased via Eventbrite.

Special thanks to Daniël van Eeden and Jean-François Gagné for their work in making this happen! Continue reading » “Percona Live Amsterdam: Community Dinner, Sep. 22nd”

## Baffling 5.7 global/status variables issues, unclean migration path

MySQL Configuration INFORMATION_SCHEMA Monitoring New Features Opinions orchestrator performance_schema Security Stored routines August 7, 2015August 19, 2015

MySQL 5.7 introduces a change in the way we query for global variables and status variables: the INFORMATION_SCHEMA.(GLOBAL|SESSION)_(VARIABLES|STATUS) tables are now deprecated and empty. Instead, we are to use the respective performance_schema.(global|session)_(variables|status) tables.

But the change goes farther than that; there is also a security change. Oracle created a pitfall of 2 changes at the same time:

1. Variables/status moved to a different table
2. Privileges required on said table

As an example, my non-root user gets:

>     mysql> show session variables like 'tx_isolation';
>     ERROR 1142 (42000): SELECT command denied to user 'normal_user'@'my_host' for table 'session_variables'

Who gets affected by this? Nearly everyone and everything.

- Your Nagios will not be able to read status variables
- Your ORM will not be able to determine session variables
- Your replication user will fail connecting (see this post by Giuseppe)
- And most everyone else.

The problem with the above is that involves two unrelated changes to your setup, which are not entirely simple to coordinate:

1. Change your app code to choose the correct schema (information_schema vs. performance_schema)
2. GRANT the permissions on your database

Perhaps at this point you still do not consider this to be a problem. You may be thinking: well, let’s first prepare by creating the GRANTs, and once that is in place, we can, at our leisure, modify the code.

Not so fast. Can you really that simply create those GRANTs? Continue reading » “Baffling 5.7 global/status variables issues, unclean migration path”

## On SHOW BINLOG/RELAYLOG EVENTS

MySQL Replication August 4, 2015

Some notes after working with SHOW BINLOG EVENTS and SHOW RELAYLOG EVENTS statements; there are a few gotchas and some interesting facts. My reflections also follow.

I’m calling these commands from orchestrator when working with Pseudo-GTID (which I do alot). I prefer to work with agent-free design, where a single, remote service can do everything: examine replication status, scan binary logs for information, and recover broken topologies via gluing together servers that were not previously directly associated.

Alas, documentation is short on these commands, and some stuff I learned the hard way.

Basically, SHOW BINLOG/RELAYLOG EVENTS commands are a poor man’s replacement to mysqlbinlog, only you can issue them on MySQL protocol, and you do not have to have the binary/relay log files locally on your host.

### Fun fact

The binary logs are called so because they are compressed. You are familiar with the binlog position you see on SHOW MASTER STATUS or SHOW SLAVE STATUS. You are familiar with the binlog position as you see it when you execute “mysqlbinlog mybinlog.001234”. The position of a new entry equals to the file size of the binary log at that time. If:

>     $ ls -l master/data/mysql-bin.015901
>     -rw-rw---- 1 user user 401408 Jul 18 02:44 master/data/mysql-bin.015901

Then the next entry will be at position 401408, as this is the file size in bytes.

And so when MySQL writes an entry to the binary log, it (of course) knows the entry’s position in the binary log, but then also immediately knows the position of the next entry.

We’ll revisit this fact later.

### Output of SHOW BINLOG/RELAYLOG EVENTS

The output of both statement depends on the binlog_format. In Statement Based Replication it may look like: Continue reading » “On SHOW BINLOG/RELAYLOG EVENTS”