Ganglia Architecture and Module Development

Ganglia
Architecture and Module Development

Ganglia
monitoring suite consists of three main parts: gmond, gmetad and
ganglia-web.

gmond	The ganglia monitoring daemon (gmond) is a lightweight service that is installed on every machine you'd like to monitor. This daemon uses a simple listen/announce protocol via XDR to collect monitoring state and then shares this information via XML over TCP. Gmond is portable and collects dozens of system metrics: CPU, memory, disk, network and process data.
gmetad	The ganglia meta daemon (gmetad) is a service that collects data from other gmetad and gmond sources and stores their state to disk in indexed round-robin databases. Gmetad provides a simple query mechanism for collecting specific information about groups of machines. Gmetad supports hierarchical delegation for creating manageable monitoring domains.
gmetric	The ganglia metric tool is a commandline application that you can use to inject custom made metrics about hosts that are being monitored by ganglia. It has the ability to spoof messages as coming from a different host in case you want to capture and report metrics from a device where you don't have gmond running (like a network or other embedded device).
gstat	The ganglia stat tool is a commandline application that you can use to query a gmond for metric information directly.
gweb	The ganglia web frontend expresses the data stored by gmetad in a graphical web interface using PHP.

Fig. Ganglia
Architecture in Cluster Mode

Ganglia-web Extension

All
of the "graph handlers"
are stored in the ../ganglia/graph.d
directory, where "ganglia"
is the top-level directory used by the webserver to publish the
various Ganglia webpages. Ganglia ships with one
general handler for metrics,
five basic reports,
and one heavily commented sample
report.

• The
  default layout of ganglia-web and default view of graphs can be
  modified according our need. For that we just need to modify some
  PHP code.
• Uses
  presentation templates so that the web site “look
  and feel” can be easily customized.

modify ../ganglia/templates/defaults/*.tpl

- Adding Custom Reports
It is possible to add new custom reports, without making any changes to the “Official” Ganglai PHP code. Adding new report is a four step process.

1. All reports should be contained in a single PHP file with the name "reportName_report.php" in the
graph.d/ directory. Obviously, replace "reportName" with something suitable.
2. The *_report function should return an associative array that contains a number of specifically named
variables example:$series,$title,$vertical_label etc.
3. Within this file, you must have a PHP function called "reportName_report" that takes a single array argument that is passed by reference (not by value!). The function definition for this will look something like this:

function temperature_report ( &$rrdtool_graph ) {
    $rrdtool_graph['vertical_label'] = 'Temperature (C)';
    $rrdtool_graph['title']          = 'CPU Temeratures';
    $rrdtool_graph['series']         = "... very long set of RRD tool RPN commands...";
}

4. Edit the $optional_graphs variable in the conf.php file to include the base name of your new report.
Thus, if the function name is reportName_report, and the PHP file is "reportName_report.php", include
only "reportName" in the $optional_graphs array.

$optional_graphs = array('packets', 'reportName');

Sample report to view cpu user
<?php

function graph_demo_report ( &$rrdtool_graph ) {

global $cpu_user_color,

$rrd_dir;

$rrdtool_graph['title'] ='==Demo Report==';

$rrdtool_graph['vertical-label'] = '==Demo Report==';

$series ="DEF:'cpu_user'='${rrd_dir}/cpu_user.rrd':'sum':AVERAGE "

. "AREA:'cpu_user'#$cpu_user_color:'==CPU User==' ";

$rrdtool_graph['series'] = $series;

return $rrdtool_graph;

}

?>

Gmond Matrix Gathering Agent Extension

- Gmetric – Out-of-process utility capable of invoking command line based metric gathering scripts

- Loadable modules capable of gathering multiple metrics or using advanced metric gathering APIs

Gmond Pluggable Metric Modules Development

- Using C

- Using Python

Using Python

- Extends the available metrics that can be gathered by Gmond

- Provided as dynamically loadable modules

- Configured through the gmond.conf

- Scheduled through Gmond rather than an external scheduler

- Module development is similar to an Apache module

- Able to produce multiple metrics from a single module

Each module must contain three mandatory functions

metric_init()

- Called once at module initialization time

- Must return a metric description dictionary or list of dictionaries

- Any other module initialization can also take place here

metric_handler() –

- may have multiple handlers

- Metric gathering handler

- Must return a single data value of the same type as specified in the metric_init() function

metric_cleanup()

- Called once at module termination time

• Does
  not return a value
  Example
  Module:

Curve_Max = 15

v = int(1)

inc = int(1)

count = 0

def metric_init(params):

global Curve_Max

if ‘CurveMax’ in params:

Curve_Max = int(params[‘CurveMax’])

d = {‘name’: ‘Curve_Metric’,

‘call_back’: curve_handler,

‘time_max': int(60),

‘value_type’: ‘uint’,

‘units’: ‘Seconds’,

‘slope’: ‘both’,

‘format’: ‘%u’,

‘description’:

‘Shows a uniform curve’}

return d

def curve_handler(name):

global v,count,inc,Curve_Max

v += inc

count += 1

if count > Curve_Max:

count = 0

inc = -inc

return int(v)

def metric_cleanup():

pass

Gmond Python Module Deployment

- Copy the .py file to python directory specified in gmond.conf file put in gmond.conf

modules {

module {

name = "python_module"

path = "/usr/lib/ganglia/modpython.so"

params = "/usr/lib/ganglia/python_modules"

}

}

- Define the metric to collection group for this module

- Restart gmond

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