documentation/specification/expected_data.txt

XML via UDP - expected data from hosts
======================================


<<< Provisional, pjm2@ukc.ac.uk >>>


Purpose of this document
------------------------

This document shall help to provide a separate party with
the knowledge required to use their own implementation of
a piece of host monitoring software.  In particular, this
document details the data that is to be expected from a
host.  This document is additional to
http://www.i-scream.org.uk/cgi-bin/docs.cgi?doc=specification/xml_via_udp.txt


Background
----------

Hosts are expected to periodically send UDP packets to the
central monitoring system.  Such packets may contain various
pieces of information about the host, such as how much free
memory is remaining on the host, etc.  Some of this data is
deemed to be 'essential', some is 'expected' and the rest
is not necessary, but shall not be ignored by the central
monitoring system server.


Specification
-------------

The UDP packet must contain a complete and well-formed
piece of XML markup, describing the data that the host is
submitting.  In the event of a piece of data containing
an invalid character, such as a "<", it is the responsibilty
of the host to format this in a valid manner, for example
by replacing all occurrences of "<" with "&lt" before it is
sent in a UDP packet to the central monitoring system server.

Alternatively, the data may be wrapped up in special CDATA
tags.  For example, if we wish to send the following text:

    <>&!"

surrounded by <test_chars> tags then we can safely send this
by wrapping it up to produce the following XML snippet:

    <test_chars><![CDATA[<>&!"]]></test_chars>

The bare minimum that a host should send is the following: -

    <packet>
    </packet>

Note that every XML tag must also have a matching closing
tag.

However, such a packet is rather useless when it is
received by the server - it does not provide any useful
information.  As such, a packet will be rejected by the
server if it does not specify the machine_name, its
I.P. address (ip), a packet sequence number (seq_no)
and a date.  Note that the date is a long integer
representing the number of seconds since the epoch.
All of these are expected to be specified as an attribute
of the packet tag.  If they are not specified here, then
the packet will be rejected.

Thus, to ensure that a packet has a chance of being
acted upon, a host must specify at least four attribute
values - machine_name, ip, date and seq_no.  These must
be formed in the style shown below.

    <packet machine_name="raptor" ip="aaa.bbb.ccc.ddd"
            date="93456245245" seq_no="1234567">
    </packet>

Note that the server may run additional 'plugin' tools
that are designed to filter/reject packets under certain
conditions.  Please check with the server administrator
if you wish to know about the specific configuration of
your central monitoring system.

The I.P. address and machine_name could be found from
the UDP packet itself, but these remain essential so
as to provide resiliance from stray packets that do not
contain any valid or useful data.

Remember that malformed XML data would be rejected by the
central monitoring system immediately, without acting upon
it.


Classification of XML data in our system
----------------------------------------


ESSENTIAL: -

The following values are ESSENTIAL in each packet.  Any
packet without these will be rejected.  They MUST be
specified as attributes of the root node ("packet"): -

    ip
    seq_no
    date
    machine_name


EXPECTED: -

The following values are EXPECTED in each packet.  All
packets are RECOMMENDED to specify these values, as the
server is designed to permanently store such data in an
easy and quick to access manner.  It is not essential to
specify such values, but it does limit the usefulness of
the central monitoring system if these values are not
specified: -

    mac_address (attribute)
    os_name (attribute)
    os_version (attribute)
    cpus *
    load *
    memory *
    swap *
    disk_free *
    disk_total *
    users (attribute)

* - These parameters are specified with tags of the same
    name.  They contain nested XML tags.  See later in
    this document for more details about that!

All of the values marked as being attributes above must be
specified as an attribute of the root tag ("packet")


OTHER: -

Any other arbitrary values may be specified by the host.
The only provision here is that they may not share the
same name as another tag or attribute within the same
heirarchical level.  The server will be able to handle
such clashes, however, it cannot be guaranteed which
of the duplicate parameters would gain priority.


Detail of a complete 'expected' XML packet via UDP
--------------------------------------------------

I shall start by showing an example of a complete
'expected' packet.  I shall then explain the contents
of it.

Here is an example of an XML packet, containing all of
the 'essential' and 'expected' data: -

<packet ip="" seq_no="" date="" machine_name=""
        mac_address="" os_name="" os_version=""
        user="">
    <cpus>
        <cpu1></cpu1>
        <cpu2></cpu2>
        <cpu3></cpu3>
    </cpus>
    <load>
        <load1><load1>
        <load5><load5>
        <load15><load15>
    </load>
    <memory>
        <free></free>
        <total></total>
    </memory>
    <swap>
        <free></free>
        <total></total>
    </swap>
    <disk_free>
        <p1></p1>
        <p2></p2>
        <p3></p3>
    </disk_free>
    <disk_total>
        <p1></p1>
        <p2></p2>
        <p3></p3>
    </disk_total>
</packet>

Note that linefeeds and spaces would normally not be present.
These are only shown above for structure clarity.

Note that all of the essential attributes have been specified
as attributes of the root node.  The expected attribute
values are also attributes of the root node.

The <cpus> tag begins a list of cpu load information.
Each subtag herein must be of the form cpux, where x is
the number of the processor in multiprocessor systems.
Note that this numbering starts from zero.

The <load> tag begins a list of system load information.
The load tag is only expected to contain 3 subtags, named
"load1", "load5" and "load15".  These represent the average
load 1 minutes ago, 5 minutes ago and 15 minutes ago
respectively.

The <memory> tag begins a list of system memory information.
This tag is only expected to contain two subtags, as shown
in the example above.  These two subtags specify how much
memory the system has free and how much memory the system
has in total.

The <swap> tag is identical in nature to the <memory> tag.

The <disk_free> tag begins a list of free disk space
information.  Each subtag must be of the form px, where
x is the number of the disk partition that is unique for
that particular system.  The value represents how much
space is free on that partition.  Note that px numbering
starts from zero.

The <disk_total> tag begins a list of total disk space,
similar in implementation to the <disk_free> tag.

Any other values and attributes may be specified in the
packet, providing they are not specified in the same
heirarchical level as another attribute or value with
the same name.


Flexibility and Minimising bandwidth
------------------------------------

The following issues still stand: -

The means of submitting host data via UDP containing XML
markup is provided so that future customisation is easily
possible.  It would be possible to easily tailor a custom
piece of host monitoring software to provide exactly what
data is desired for adequate monitoring.

Some of the XML markup demonstrated above contains a lot
of rendundant features.  For example, it is not necessary
to lay the contents out neatly (although this certainly
helps visualise the contents).

The amount of data sent within each UDP packet may be (in
some cases, vastly) reduced by using some of the ideas
described below: -

  - Remove unnecessary linefeeds and 'white space'

  - If a single piece of data is to be represented, it
    will usually occupy less space if it is stored as
    an attribute to a tag, rather than within a pair
    of tags.

  - Comments within the XML may be useful for testing
    purposes, however, the server ignores all comments
    so these can be removed to reduce packet sizes.

Taking the above into account, here is an example of some
ideally formed XML to be contained within a UDP packet: -

    <packet machine_name="raptor" ip="aaa.bbb.ccc.ddd"
    ><freespace><drive1>23677</drive1><drive2>23534</d
    rive2><drive3>10390</drive3></freespace></packet>

Notice how all unnecessary 'white space' and linefeeds have
been removed.  The comment has also been removed.  Values
such as "machine_name" and "ip" have both been stored as an
attribute of the root node ("packet") as this results in
a smaller packet size.


About
-----

This document was written by Paul Mutton [pjm2@ukc.ac.uk]
for use by the team working on a 3rd year Computer Science 
project called "i-scream". More details can be found on the 
project website - http://www.i-scream.org.uk

 
Revision:	1.3
Committed:	Tue Nov 28 11:51:32 2000 UTC (24 years ago) by pjm2
Content type:	text/plain
Branch:	MAIN
Changes since 1.2:	+3 -3 lines
Log Message:	Corrected the names of the load tag trio.
#	User	Rev	Content
1	pjm2	1.1	XML via UDP - expected data from hosts
2			======================================
3
4
5			<<< Provisional, pjm2@ukc.ac.uk >>>
6
7
8			Purpose of this document
9			------------------------
10
11			This document shall help to provide a separate party with
12			the knowledge required to use their own implementation of
13			a piece of host monitoring software. In particular, this
14			document details the data that is to be expected from a
15			host. This document is additional to
16			http://www.i-scream.org.uk/cgi-bin/docs.cgi?doc=specification/xml_via_udp.txt
17
18
19			Background
20			----------
21
22			Hosts are expected to periodically send UDP packets to the
23			central monitoring system. Such packets may contain various
24			pieces of information about the host, such as how much free
25			memory is remaining on the host, etc. Some of this data is
26			deemed to be 'essential', some is 'expected' and the rest
27			is not necessary, but shall not be ignored by the central
28			monitoring system server.
29
30
31			Specification
32			-------------
33
34			The UDP packet must contain a complete and well-formed
35			piece of XML markup, describing the data that the host is
36			submitting. In the event of a piece of data containing
37			an invalid character, such as a "<", it is the responsibilty
38			of the host to format this in a valid manner, for example
39			by replacing all occurrences of "<" with "&lt" before it is
40			sent in a UDP packet to the central monitoring system server.
41
42			Alternatively, the data may be wrapped up in special CDATA
43			tags. For example, if we wish to send the following text:
44
45			<>&!"
46
47			surrounded by <test_chars> tags then we can safely send this
48			by wrapping it up to produce the following XML snippet:
49
50			<test_chars><![CDATA[<>&!"]]></test_chars>
51
52			The bare minimum that a host should send is the following: -
53
54			<packet>
55			</packet>
56
57			Note that every XML tag must also have a matching closing
58			tag.
59
60			However, such a packet is rather useless when it is
61			received by the server - it does not provide any useful
62			information. As such, a packet will be rejected by the
63			server if it does not specify the machine_name, its
64			I.P. address (ip), a packet sequence number (seq_no)
65	pjm2	1.2	and a date. Note that the date is a long integer
66	pjm2	1.1	representing the number of seconds since the epoch.
67			All of these are expected to be specified as an attribute
68			of the packet tag. If they are not specified here, then
69			the packet will be rejected.
70
71			Thus, to ensure that a packet has a chance of being
72			acted upon, a host must specify at least four attribute
73			values - machine_name, ip, date and seq_no. These must
74			be formed in the style shown below.
75
76			<packet machine_name="raptor" ip="aaa.bbb.ccc.ddd"
77			date="93456245245" seq_no="1234567">
78			</packet>
79
80			Note that the server may run additional 'plugin' tools
81			that are designed to filter/reject packets under certain
82			conditions. Please check with the server administrator
83			if you wish to know about the specific configuration of
84			your central monitoring system.
85
86			The I.P. address and machine_name could be found from
87			the UDP packet itself, but these remain essential so
88			as to provide resiliance from stray packets that do not
89			contain any valid or useful data.
90
91			Remember that malformed XML data would be rejected by the
92			central monitoring system immediately, without acting upon
93			it.
94
95
96			Classification of XML data in our system
97			----------------------------------------
98
99
100			ESSENTIAL: -
101
102			The following values are ESSENTIAL in each packet. Any
103			packet without these will be rejected. They MUST be
104			specified as attributes of the root node ("packet"): -
105
106			ip
107			seq_no
108			date
109			machine_name
110
111
112			EXPECTED: -
113
114			The following values are EXPECTED in each packet. All
115			packets are RECOMMENDED to specify these values, as the
116			server is designed to permanently store such data in an
117			easy and quick to access manner. It is not essential to
118			specify such values, but it does limit the usefulness of
119			the central monitoring system if these values are not
120			specified: -
121
122			mac_address (attribute)
123			os_name (attribute)
124			os_version (attribute)
125			cpus *
126			load *
127			memory *
128			swap *
129			disk_free *
130			disk_total *
131			users (attribute)
132
133			* - These parameters are specified with tags of the same
134			name. They contain nested XML tags. See later in
135			this document for more details about that!
136
137			All of the values marked as being attributes above must be
138			specified as an attribute of the root tag ("packet")
139
140
141			OTHER: -
142
143			Any other arbitrary values may be specified by the host.
144			The only provision here is that they may not share the
145			same name as another tag or attribute within the same
146			heirarchical level. The server will be able to handle
147			such clashes, however, it cannot be guaranteed which
148			of the duplicate parameters would gain priority.
149
150
151			Detail of a complete 'expected' XML packet via UDP
152			--------------------------------------------------
153
154			I shall start by showing an example of a complete
155			'expected' packet. I shall then explain the contents
156			of it.
157
158			Here is an example of an XML packet, containing all of
159			the 'essential' and 'expected' data: -
160
161			<packet ip="" seq_no="" date="" machine_name=""
162			mac_address="" os_name="" os_version=""
163			user="">
164			<cpus>
165			<cpu1></cpu1>
166			<cpu2></cpu2>
167			<cpu3></cpu3>
168			</cpus>
169			<load>
170			<load1><load1>
171			<load5><load5>
172	pjm2	1.3	<load15><load15>
173	pjm2	1.1	</load>
174			<memory>
175			<free></free>
176			<total></total>
177			</memory>
178			<swap>
179			<free></free>
180			<total></total>
181			</swap>
182			<disk_free>
183			<p1></p1>
184			<p2></p2>
185			<p3></p3>
186			</disk_free>
187			<disk_total>
188			<p1></p1>
189			<p2></p2>
190			<p3></p3>
191			</disk_total>
192			</packet>
193
194			Note that linefeeds and spaces would normally not be present.
195			These are only shown above for structure clarity.
196
197			Note that all of the essential attributes have been specified
198			as attributes of the root node. The expected attribute
199			values are also attributes of the root node.
200
201			The <cpus> tag begins a list of cpu load information.
202			Each subtag herein must be of the form cpux, where x is
203			the number of the processor in multiprocessor systems.
204			Note that this numbering starts from zero.
205
206			The <load> tag begins a list of system load information.
207			The load tag is only expected to contain 3 subtags, named
208	pjm2	1.3	"load1", "load5" and "load15". These represent the average
209			load 1 minutes ago, 5 minutes ago and 15 minutes ago
210	pjm2	1.1	respectively.
211
212			The <memory> tag begins a list of system memory information.
213			This tag is only expected to contain two subtags, as shown
214			in the example above. These two subtags specify how much
215			memory the system has free and how much memory the system
216			has in total.
217
218			The <swap> tag is identical in nature to the <memory> tag.
219
220			The <disk_free> tag begins a list of free disk space
221			information. Each subtag must be of the form px, where
222			x is the number of the disk partition that is unique for
223			that particular system. The value represents how much
224			space is free on that partition. Note that px numbering
225			starts from zero.
226
227			The <disk_total> tag begins a list of total disk space,
228			similar in implementation to the <disk_free> tag.
229
230			Any other values and attributes may be specified in the
231			packet, providing they are not specified in the same
232			heirarchical level as another attribute or value with
233			the same name.
234
235
236			Flexibility and Minimising bandwidth
237			------------------------------------
238
239			The following issues still stand: -
240
241			The means of submitting host data via UDP containing XML
242			markup is provided so that future customisation is easily
243			possible. It would be possible to easily tailor a custom
244			piece of host monitoring software to provide exactly what
245			data is desired for adequate monitoring.
246
247			Some of the XML markup demonstrated above contains a lot
248			of rendundant features. For example, it is not necessary
249			to lay the contents out neatly (although this certainly
250			helps visualise the contents).
251
252			The amount of data sent within each UDP packet may be (in
253			some cases, vastly) reduced by using some of the ideas
254			described below: -
255
256			- Remove unnecessary linefeeds and 'white space'
257
258			- If a single piece of data is to be represented, it
259			will usually occupy less space if it is stored as
260			an attribute to a tag, rather than within a pair
261			of tags.
262
263			- Comments within the XML may be useful for testing
264			purposes, however, the server ignores all comments
265			so these can be removed to reduce packet sizes.
266
267			Taking the above into account, here is an example of some
268			ideally formed XML to be contained within a UDP packet: -
269
270			<packet machine_name="raptor" ip="aaa.bbb.ccc.ddd"
271			><freespace><drive1>23677</drive1><drive2>23534</d
272			rive2><drive3>10390</drive3></freespace></packet>
273
274			Notice how all unnecessary 'white space' and linefeeds have
275			been removed. The comment has also been removed. Values
276			such as "machine_name" and "ip" have both been stored as an
277			attribute of the root node ("packet") as this results in
278			a smaller packet size.
279
280
281			About
282			-----
283
284			This document was written by Paul Mutton [pjm2@ukc.ac.uk]
285			for use by the team working on a 3rd year Computer Science
286			project called "i-scream". More details can be found on the
287			project website - http://www.i-scream.org.uk
288
289