Host¶

This module defined the naghelp Host object.

The Host object will store all informations about the equipment to monitor. It could be for exemple :

The hostname

Host IP address

The user login

The user password

The snmp community

…

One can add some additional data during the plugin execution, they will be persistent accross all plugin executions (plugin objects call save_data() and load_data() methods). This is useful for :

Counters

Gauges

Timestamps

Flags

…

Informations come from 3 sources in this order :

From a database ( text file, sqlite, mysql … )

From environment variables

From command line

Informations from command line have priority over environment vars which have priority over those from database.

class naghelp.Host(plugin)¶

Contains equipment informations

Host object is a dict with some additional methods.

Parameters:	plugin (`Plugin`) – The plugin object that is used to monitor the equipment

Informations can be accessed and modified by 2 ways :

By attribute

By Index

To save and load custom data, one could do a save_data() and load_data() but this is automatically done by the plugin itself (see naghelp.ActivePlugin.run())

Examples :

>>> os.environ['NAGIOS_HOSTNAME']='host_to_be_monitored'
>>> plugin = ActivePlugin()
>>> host = Host(plugin)
>>> print host.name
host_to_be_monitored
>>> host.my_custom_data = 'last check time'
>>> print host.my_custom_data
last check time
>>> print host['my_custom_data']
last check time
>>> host.save_data()
>>> host._get_persistent_filename()
'/tmp/naghelp/host_to_be_monitored_persistent_data.json'
>>> print open(host._get_persistent_filename()).read() 
{
    "name": "host_to_be_monitored",
    "my_custom_data": "last check time"
}

>>> os.environ['NAGIOS_HOSTNAME']='host_to_be_monitored'
>>> plugin = ActivePlugin()
>>> host = Host(plugin)
>>> print host.my_custom_data

>>> host.load_data()
>>> print host.my_custom_data
last check time

_get_env_to_param()¶

Returns a dict for the environment variable to extract

The keys are the environment variables to extract, the values are the attribute name to use for the Host object.

Only a few environment variables are automatically extracted, they are renamed when saved into Host object :

Environment Variables Stored as

NAGIOS_HOSTNAME name

NAGIOS_HOSTALIAS alias

NAGIOS_HOSTADDRESS ip

NAGIOS_HOSTGROUPNAMES groups

NAGIOS_HOSTGROUPNAME group

_get_params_from_db(hostname)¶

Get host informations from database

Getting informations from a database is optionnal. If needed, it is the developer responsibility to subclass Host class and redefine the method _get_params_from_db(hostname) that returns a dict with informations about hostname. In this method, the developer must also load persistent data that may come from a same cache file as the database. The default behaviour for this method is only to load persistent data from a database flat file (.json).

Parameters:	hostname (str) – The name of the equipment as declared in Nagios configuration files.
Returns:	A dictionary that contains equipment informations AND persistent data merged.
Return type:	dict

Example

Here is an example of _get_params_from_db() override where informations about a monitored host are stored in a json file located at DB_JSON_FILE

class MonitoredHost(Host):
    def _get_params_from_db(self,hostname):
        # The first step MUST be to read the persistent data file ( = cache file )
        params = self._plugin.load_data(self._get_persistent_filename()) or DictExt()

        # Check whether the database file has changed
        db_file_modif_time = int(os.path.getmtime(DB_JSON_FILE))
        if db_file_modif_time == params['db_file_modif_time']:
            # if not, return the cached data
            return params

        # If database file has changed :
        db = json.load(open(DB_JSON_FILE))
        # find hostname in db :
        for h in db.monitored_hosts:
            if h['datas']['hostname'] == hostname:
                # merge the new data into the persistent data dict (will be cached)
                params.update(h.datas)
                params['db_file_modif_time'] = db_file_modif_time
                params['name'] = params.get('hostname','noname')
                return params
        return params

Note

You can do about the same for SQlite or MySQL, do not forget to load persistent data file as a first step and merge data from database after. Like the above example, you can use the persistent data json file as a cache for your database. By this way, persistent data AND database data are saved in the same file within a single operation. The dictionary returned by this method will be saved automatically by the naghelp.ActivePlugin.run() method as persistent data.

_get_persistent_filename()¶

Get the full path for the persisten .json file

It uses persistent_filename_pattern to get the file pattern, and apply the hostname to build the full path.

debug()¶: Log Host informations for debug

Note

To see debug on python console, call naghelp.activate_debug()

get(k[, d]) → D[k] if k in D, else d. d defaults to None.¶

load_data()¶

load data to the Host object

That is from database and/or persistent file then from environment variables and then from command line.

persistent_filename_pattern = '/tmp/naghelp/%s_persistent_data.json'¶: Default persistent .json file path pattern (note the %s that will be replaced by the hostname)

save_data()¶

Save data to a persistent place

It actually saves the whole dict into a .json file. This is automatically called by the :meth:naghelp.ActivePlugin.run method.

to_list(lst, defvalue='-')¶

Formats a list of strings with Host informations

It works like to_str() except that the input is a list of strings : This useful when a text has been splitted into lines.

Parameters:	str (str) – A format string defvalue (str) – String to display when a data is not available
Returns:	The list with formatted string
Return type:	list

Examples

>>> os.environ['NAGIOS_HOSTNAME']='host_to_be_monitored'
>>> os.environ['NAGIOS_HOSTADDRESS']='192.168.0.33'
>>> plugin = ActivePlugin()
>>> host = Host(plugin)
>>> host.load_data()
>>> lst = ['{name} as got IP={ip} and custom data "{my_custom_data}"',
... 'Not available data are replaced by a dash: {other_data}']
>>> print host.to_list(lst)  
[u'host_to_be_monitored as got IP=192.168.0.33 and custom data "last check time"',
'Not available data are replaced by a dash: -']

Note

As you noticed, NAGIOS_HOSTNAME environment variable is stored as name in Host object and NAGIOS_HOSTADDRESS as ip. my_custom_data is a persistent data that has been automatically loaded because set into a previous example.

to_str(str, defvalue='-')¶

Formats a string with Host informations

Not available data are replaced by a dash

Parameters:	str (str) – A format string defvalue (str) – String to display when a data is not available
Returns:	the formatted string
Return type:	str

Examples

>>> os.environ['NAGIOS_HOSTNAME']='host_to_be_monitored'
>>> os.environ['NAGIOS_HOSTADDRESS']='192.168.0.33'
>>> plugin = ActivePlugin()
>>> host = Host(plugin)
>>> host.load_data()
>>> print host.to_str('{name} as got IP={ip} and custom data "{my_custom_data}"')
host_to_be_monitored as got IP=192.168.0.33 and custom data "last check time"
>>> print host.to_str('Not available data are replaced by a dash: {other_data}')
Not available data are replaced by a dash: -
>>> print host.to_str('Or by whatever you want: {other_data}','N/A')
Or by whatever you want: N/A

Note

As you noticed, NAGIOS_HOSTNAME environment variable is stored as name in Host object and NAGIOS_HOSTADDRESS as ip. my_custom_data is a persistent data that has been automatically loaded because set into a previous example.