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https://github.com/deniszh/collectd-iostat-python

Collectd-iostat-python is an iostat plugin for collectd that allows you to graph Linux iostat metrics in graphite or other output formats that are supported by collectd.
https://github.com/deniszh/collectd-iostat-python

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Collectd-iostat-python is an iostat plugin for collectd that allows you to graph Linux iostat metrics in graphite or other output formats that are supported by collectd.

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README 

        
collectd-iostat-python

======================



`collectd-iostat-python` is an `iostat` plugin for Collectd that allows you to

graph Linux `iostat` metrics in Graphite or other output formats that are

supported by Collectd.



This plugin (and mostly this `README`) is rewrite of the

[collectd-iostat](https://github.com/keirans/collectd-iostat) from Ruby to Python

using the

[collectd-python](http://collectd.org/documentation/manpages/collectd-python.5.shtml)

plugin.



Why?

----



Disk performance is quite crucial for most of modern server

applications, especially databases (e.g. MySQL - check out [this

slides](http://www.percona.com/live/mysql-conference-2013/sessions/monitoring-io-performance-using-iostat-and-pt-diskstats)

from Percona Live conference).



Although Collectd [provides disk statistics out of the

box](https://collectd.org/wiki/index.php/Plugin:Disk), graphing the metrics as

shown by `iostat` was found to be more useful and graphic, because `iostat`

reports usage of block devices, partitions, multipath devices and LVM volumes.



Also this plugin was rewritten in Python, because it's a preferable language for

siteops' tools on my current job, and choice of using

[collectd-python](http://collectd.org/documentation/manpages/collectd-python.5.shtml)

instead of

[collectd-exec](https://collectd.org/documentation/manpages/collectd-exec.5.shtml)

was made for performance and stability reasons.



How?

----



`collectd-iostat-python` functions by calling `iostat` with some predefined

intervals and push that data to Collectd using Collectd `python` plugin.



Collectd can be then configured to write the Collected data into many output

formats that are supported by it's write plugins, such as `graphite`, which was

the primary use case for this plugin.



Setup

-----



Deploy the Collectd Python plugin into a suitable plugin directory for your

Collectd instance.



Configure Collectd's `python` plugin to execute the `iostat` plugin using a

stanza similar to the following:



```



    Globals true



    ModulePath "/usr/lib/collectd/plugins/python"

    Import "collectd_iostat_python"



    

        Path "/usr/bin/iostat"

        Interval 2

        Count 2

        Verbose false

        NiceNames false

        PluginName collectd_iostat_python

    



```



If you need to select a subset of the devices listed by iostat you can utilize 

`DisksRegex` to write a regular expression to select the appropriate devices for your environment.

```

# Only collect data for these devices

DisksRegex "^[hs]d"

```



In large and changing environments it benefital if your device statistics maintain the same device names across reboots or reconfigurations so that historical data is not compromised. This can be achived by enabling persistent naming based on udev attributes.

Simply enable persistent naming by setting UdevNameAttr to the attribute you want to use to name your devices. A good example would be ID_SERIAL which is persistent and unique per device. To find useful attributes you can use `udevadm info /dev/`

```

# Enable persistent device naming

UdevNameAttr "ID_SERIAL"

```



Please note that you need to install [pyudev](https://pyudev.readthedocs.io/en/latest/) Python module for this functionality.



In a multipath environment, a single physical disk can be exposed as two /dev entries. A device mapper entry is created by multipathd to handle interacting with the disk. Setting SkipPhysicalMultipath causes the physical multipath disks to be skipped, and only the dm- entry to be processed. Physical non-multipathed disks will be processed normally. Enable NoDisplayDMName as well to display the /dev entry instead of the registered device name.



```

SkipPhysicalMultipath true

NoDisplayDMName true

```



Please note that you need to install [pyudev](https://pyudev.readthedocs.io/en/latest/) Python module for this functionality.



If you would like to use more legible metric names (e.g.

`requests_merged_per_second-read` instead of `rrqm_s`), you have to set

`NiceNames` to `true` and add load the custom types database (see the

`iostat_types.db` file) by adding the following into the Collectd config file:



```

# The default Collectd types database

TypesDB "/usr/share/collectd/types.db"

# The custom types database

TypesDB "/usr/share/collectd/iostat_types.db"

```



Once functioning, the `iostat` data should then be visible via your various

output plugins. Please note, that you need to restart collectd service after

plugin installation, as usual.



In the case of Graphite, Collectd should be writing data in the

`hostname_domain_tld.collectd_iostat_python.DEVICE.column-name` style namespaces.

Symbols like `/`, `-` and `%` in metric names (but not in device names) are

automatically replaced by underscores (i.e. `_`).



Please note that this plugin will take only last line of `iostat`

output, so big `Count` numbers also have no sense, but `Count` needs

to be more than `1` to get actual and not historical data. The data

collection will run every `Interval * (Count-1)` seconds and this

value needs to be less than `Collectd.INTERVAL`. Default

`Collectd.INTERVAL` is 10 seconds, so default value of `Count=2` and

`Interval=2` works quite well for me.



Technical notes

---------------



For parsing `iostat` output, I'm using

[jakamkon's](https://bitbucket.org/jakamkon)

[python-iostat](https://bitbucket.org/jakamkon/python-iostat) Python module, but

as an internal part of the script instead of a separate module because of couple

of fixes I have made (using Kbytes instead of blocks, adding -N to `iostat` for

LVM endpoint resolving, migration to `subprocess` module as replacement of

deprecated `popen3`, `objectification` etc).



Compatibility

-------------



Plugin was tested on Ubuntu 12.04/14.04 (Collectd 5.2/5.3/5.4, Python 2.7) and

CentOS (Collectd 5.4 / Python 2.6). Please note that if running Python 2.6 or

older (i.e. on CentOS and its derivatives) we trying to restore `SIGCHLD` signal

handler to mitigate a known [bug](http://bugs.python.org/issue1731717) which

according to the Collectd's

[documentation](https://collectd.org/documentation/manpages/collectd-python.5.shtml#configuration)

breaks the `exec` plugin, unfortunately.



TODO

----



* Maybe some data aggregation needed (e.g. we can use some max / avg aggregation

of data across intervals instead of picking last line of `iostat` output).

* The `Disks` parameter could support regexp.



Additional reading

------------------



* [man iostat(1)](http://linux.die.net/man/1/iostat)

* [Custom Collectd Plug-ins for Linux](http://support.rightscale.com/12-Guides/RightScale_101/08-Management_Tools/Monitoring_System/Writing_custom_collectd_plugins/Custom_Collectd_Plug-ins_for_Linux)

* [python-iostat](https://bitbucket.org/jakamkon/python-iostat)

* [collectd-iostat](https://github.com/keirans/collectd-iostat)

* [Graphite @ The Architecture of Open Source Applications](http://www.aosabook.org/en/graphite.html)



License

-------



[MIT](http://mit-license.org/)



Support

-------



Please do not send me PMs in Twitter with issues. Just open an [issue](https://github.com/deniszh/collectd-iostat-python/issues) on [projects' Github](https://github.com/deniszh/collectd-iostat-python) instead and I'll respond ASAP!



Contact

-------



[Denis Zhdanov](mailto:[email protected])

([@deniszh](http://twitter.com/deniszh))