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10 Newer Entries Showing entries 31 to 40 of 170 10 Older Entries

Displaying posts with tag: monitoring (reset)

Monitoring DML/slow queries with graphite
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pt-query-digest, Anemometer or "Anemomaster" do a great job of analysing your queries and giving you visibility into what's going on with your MySQL servers. However, the place where the query digests are written is just some MySQL tables on some server. Do you have monitoring/alerts on that table? How will you verify a specific query does not exceed some runtime/execution …

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"Anemomaster": DML visibility. Your must-do for tomorrow
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Here's our take of master DML query monitoring at Outbrain (presented April 2014). It took a half-day to code, implement, automate and deploy, and within the first hour of work we managed to catch multiple ill-doing services and scripts. You might want to try this out for yourself.

What's this about?

What queries do you monitor on your MySQL servers? Many don't monitor queries at all, and only look up slow queries on occasion, using …

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mycheckpoint, discontinued
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Time to admit to myself: mycheckpoint has to be discontinued.

I started mycheckpoint back in 2009, as a free & open source lightweight monitoring tool for MySQL. Over some years it evolved and became an actual (lightweight) monitoring solution, used by many. It has a unique and original design, which, alas, is also its bane.

mycheckpoint uses the relational model & SQL to store and query monitored metrics. This leads to quite a sophisticated service, which can make practically anything visible to the user. The raw data is just numbers. …

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About Nagios monitoring in real example
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Now it’s time to setup proper monitoring to avoid unpleasant surprises in future.

There are two major problems the monitoring solves: alerting and trending. Alerting is to notify a responsible person about some major event like service stopped working. Trending is to track the change of something over time – disk or memory usage over time, replication lag etc.

This post will be about alerting with Nagios.

The major problem with most of Nagios setups I’ve seen is excessive amount of false positives. This kills whole …

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Contain oom-killer
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Amazon micro instances is the great start option for small websites. Learn how to contain oom-killer that may make wrong decision.

oom-killer as MySQL vs Apache arbiter

When it comes to competition for memory oom-killer steps in. I run Apache and MySQL on the same box. This you should probably never do, but I thought that on my tiny setup they will get along. That’s not true. It started when first users came in. The system ran quickly out of memory:

Feb  5 03:48:26 app-01 kernel: [3313052.688189] httpd invoked oom-killer: gfp_mask=0x201da, order=0, oom_adj=0, …
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Seconds_behind_master vs. Absolute slave lag
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I am unable to bring myself to trust the Seconds_behind_master value on SHOW SLAVE STATUS. Even with MySQL 5.5's CHANGE MASTER TO ... MASTER_HEARTBEAT_PERIOD (good thing, applied when no traffic goes from master to slave) it's easy and common to find fluctuations in Seconds_behind_master value.

And, when sampled by your favourite monitoring tool, this often leads to many false negatives.

At Outbrain we use HAProxy as proxy to our slaves, on multiple clusters. More about that in a future post. What's important here is that our decision …

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Bash script: report largest InnoDB files
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The following script will report the largest InnoDB tables under the data directory: schema, table & length in bytes. The tables could be non-partitioned, in which case this is simply the size of the corresponding .ibd file, or they can be partitioned, in which case the reported size is the sum of all partition files. It is assumed tables reside in their own tablespace files, i.e. created with innodb_file_per_table=1.

(
    mysql_datadir=$(grep datadir /etc/my.cnf | cut -d "=" -f 2)
    cd $mysql_datadir
    for frm_file in $(find . -name "*.frm")
    do
        tbl_file=${frm_file//.frm/.ibd} …
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Innotop: A real-time, advanced investigation tool for MySQL
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GUI monitoring tools for MySQL are not always suitable for all our needs or situations. Most of them are designed to provide historical views into what happens to our database over time rather then real-time insight into current MySQL server status. Excellent free tools for this include Cacti, Zabbix, Ganglia, …

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Trick: recovering from "no space left on device" issues with MySQL
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Just read Ronald Bradford's post on an unnecessary 3am (emergency) call. I sympathize! Running out of disk space makes for some weird MySQL behaviour, and in fact whenever I encounter weird behaviour I verify disk space.

But here's a trick I've been using for years to avoid such cases and to be able to recover quickly. It helped me on such events as running out of disk space during ALTER TABLEs or avoiding purging of binary logs when slave is known to be under maintenance.

Ronald suggested it -- just put a dummy …

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By all means, learn from my mistakes as a DBA!
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Here are 3 recent ' oops... wish I hadn't done that :/ ' mistakes I've made since joining moz that you might as well avoid (I'm sure there will be more, but they better not be the same)

Reviewing config files for MySQL, but not all of the defaults 

    We recently migrated a few MySQL databases to a new datacenter, and took advantage of the migration to upgrade the MySQL version(s) at the

10 Newer Entries Showing entries 31 to 40 of 170 10 Older Entries

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