documentation/specification/spec-realtime.txt

I-Scream Specification Outline (Realtime side only)
===================================================

ajm4, 30/10/2000
tdb1, 30/10/2000

System Component Startup
************************

CORE
----


Client Interface
----------------
The Client Interface is essentially just one component with 
a series of lists within it. When run it should, obviously, 
create an instance of the Client Interface, and then bind 
this to the ORB and register with the naming service. It 
then needs to construct the "local clients". These clients 
communicate with the system using the same interface as the 
external clients, but they are tailored to specific 
purposes, such as E-Mail alerts, and SMS alerts. The Client 
Interface then listens on a "well known" address for clients 
to request a connection.

Filter
------
The filter is broken down into three main subcomponents. 

  - Filter Manager
      The Filter Manager is responsible for managing which 
      filters are used by the hosts. The Filter Manager is 
      available at a "well known" location which is pre-
      programmed into the hosts. The Filter Manager is 
      responsible for creating and managing the other 
      components of the filter system.
  
  - Main Filter
      The Main Filter is the single point that links back 
      into the CORE of the system. It will connect to the 
      DBI and the CLI to deliver data.
  
  - Filters
      There can be multipler Filters, and these are the 
      "front line" to the hosts. They all link back to the 
      Main Filter to send data into the system. It is 
      possible to run these Filters on any machine, allowing 
      management of data flow.

At startup a Filter Manager object is activated at the "well 
known" location (probably a given machine name at a 
predefined port). The Filter Manager will create an instance 
of the Main Filter, and any Filters under it's control. It 
should also bind itself to the ORB and register with the 
naming service. Through some mechanism the other Filters, 
elsewhere on the network, will register with the Filter 
Manager. The Filter Manager will need to tell each Filter 
the location of the Main Filter upon registering. The Filter 
Manager will then be in a position to receive connections 
from hosts and pass them off to Filters.

System Running State
********************

CORE
----


Client Interface
----------------
In the running state the Client Interface is always 
listening for clients on the "well known" address. When a 
connection is received it is passed in to the main Client 
Interface and the client is queried about which hosts it 
wishes to receive information about. This is then stored in 
an internal "routing table" so the Client Interface knows 
which hosts to send the information on to. This routing 
table is constructed with this form;

  host1: client1 client2 client5
  host2: client2
  host3: client3 client4
  host4: client1 client3

This design is such that when a piece of information is 
recieved from a host the Client Interface can immediately 
see which clients wish to receive this data, without too 
much searching.

The "local clients" function just like any other client, 
although they are local, in that they will wish to receive 
information about hosts they are interested in. However, 
they will contain a lot more logic, and be required to work 
out who wants to be alerted about what, and when. They will 
also be responsible for sending the alert.

Filter
------
When a host first loads up it knows where to locate the 
Filter Manager because it's located at a "well known" 
location. The host will fire up a TCP connection to the 
Filter Manager to announce itself. The Filter Manager will 
use some method (logically) to allocate a Filter to the 
host. The Filter Manager should base this decision on 
various factors, such as the load on the selection of 
filters, and possibly the location in relation to the host. 
The host will then be directed to this Filter for all 
further communications.

As the system runs the host will send data with (maybe) UDP 
to the Filter (that it's been allocated to). This choice has 
been made because it puts less onus on the host to make the 
connection, rather the data is just sent out. However, to 
ensure that the data isn't just disappearing into the depths 
of the network a periodic heartbeat will occur (at a 
predefined interval) over TCP to the Filter. This heartbeat 
can be used as a form of two-way communication, ensuring 
that everything is ok, and if required, to send any 
information back to the host. This heartbeat must occur 
otherwise the server may infer the host has died.

This could link in to alerting. An amber alert could be 
initiated for a host if the server stops receiving UDP 
packets, but an red alert be raised if the heartbeat doesn't 
occur.

If, for some reason, the Filter were to disappear the host 
should fall back on it's initial discovering mechanism - ie. 
contacting the Filter Manager at it's "well known" location. 
The host should report that it's lost it's Filter (so the 
Filter Manager can investigate and remove from it's list of 
Filters), and then the Filter Manager will reassign a new 
Filter to the host. Communication can then continue.

The idea of plugins to the Filters has been introduced. 
These plugins will implement a predefined plugin interface, 
and can be chained together at the Filter. Using the 
interface we can easily add future plugins that can do 
anything from parsing new data formats, to implementing 
encryption algorithms. The Filter will pass incoming data to 
each plugin in turn that it has available, and then finally 
pass the data on to the Main Filter. The Filter need not 
have any real knowledge about the content of the data.
Revision:	1.3
Committed:	Mon Oct 30 21:45:33 2000 UTC (23 years, 6 months ago) by tdb
Content type:	text/plain
Branch:	MAIN
Changes since 1.2:	+43 -9 lines
Log Message:	Written the section on the Client Interface, although it probably needs some more work.
#	Content
1	I-Scream Specification Outline (Realtime side only)
2	===================================================
3
4	ajm4, 30/10/2000
5	tdb1, 30/10/2000
6
7	System Component Startup
8	************************
9
10	CORE
11	----
12
13
14	Client Interface
15	----------------
16	The Client Interface is essentially just one component with
17	a series of lists within it. When run it should, obviously,
18	create an instance of the Client Interface, and then bind
19	this to the ORB and register with the naming service. It
20	then needs to construct the "local clients". These clients
21	communicate with the system using the same interface as the
22	external clients, but they are tailored to specific
23	purposes, such as E-Mail alerts, and SMS alerts. The Client
24	Interface then listens on a "well known" address for clients
25	to request a connection.
26
27	Filter
28	------
29	The filter is broken down into three main subcomponents.
30
31	- Filter Manager
32	The Filter Manager is responsible for managing which
33	filters are used by the hosts. The Filter Manager is
34	available at a "well known" location which is pre-
35	programmed into the hosts. The Filter Manager is
36	responsible for creating and managing the other
37	components of the filter system.
38
39	- Main Filter
40	The Main Filter is the single point that links back
41	into the CORE of the system. It will connect to the
42	DBI and the CLI to deliver data.
43
44	- Filters
45	There can be multipler Filters, and these are the
46	"front line" to the hosts. They all link back to the
47	Main Filter to send data into the system. It is
48	possible to run these Filters on any machine, allowing
49	management of data flow.
50
51	At startup a Filter Manager object is activated at the "well
52	known" location (probably a given machine name at a
53	predefined port). The Filter Manager will create an instance
54	of the Main Filter, and any Filters under it's control. It
55	should also bind itself to the ORB and register with the
56	naming service. Through some mechanism the other Filters,
57	elsewhere on the network, will register with the Filter
58	Manager. The Filter Manager will need to tell each Filter
59	the location of the Main Filter upon registering. The Filter
60	Manager will then be in a position to receive connections
61	from hosts and pass them off to Filters.
62
63	System Running State
64	********************
65
66	CORE
67	----
68
69
70	Client Interface
71	----------------
72	In the running state the Client Interface is always
73	listening for clients on the "well known" address. When a
74	connection is received it is passed in to the main Client
75	Interface and the client is queried about which hosts it
76	wishes to receive information about. This is then stored in
77	an internal "routing table" so the Client Interface knows
78	which hosts to send the information on to. This routing
79	table is constructed with this form;
80
81	host1: client1 client2 client5
82	host2: client2
83	host3: client3 client4
84	host4: client1 client3
85
86	This design is such that when a piece of information is
87	recieved from a host the Client Interface can immediately
88	see which clients wish to receive this data, without too
89	much searching.
90
91	The "local clients" function just like any other client,
92	although they are local, in that they will wish to receive
93	information about hosts they are interested in. However,
94	they will contain a lot more logic, and be required to work
95	out who wants to be alerted about what, and when. They will
96	also be responsible for sending the alert.
97
98	Filter
99	------
100	When a host first loads up it knows where to locate the
101	Filter Manager because it's located at a "well known"
102	location. The host will fire up a TCP connection to the
103	Filter Manager to announce itself. The Filter Manager will
104	use some method (logically) to allocate a Filter to the
105	host. The Filter Manager should base this decision on
106	various factors, such as the load on the selection of
107	filters, and possibly the location in relation to the host.
108	The host will then be directed to this Filter for all
109	further communications.
110
111	As the system runs the host will send data with (maybe) UDP
112	to the Filter (that it's been allocated to). This choice has
113	been made because it puts less onus on the host to make the
114	connection, rather the data is just sent out. However, to
115	ensure that the data isn't just disappearing into the depths
116	of the network a periodic heartbeat will occur (at a
117	predefined interval) over TCP to the Filter. This heartbeat
118	can be used as a form of two-way communication, ensuring
119	that everything is ok, and if required, to send any
120	information back to the host. This heartbeat must occur
121	otherwise the server may infer the host has died.
122
123	This could link in to alerting. An amber alert could be
124	initiated for a host if the server stops receiving UDP
125	packets, but an red alert be raised if the heartbeat doesn't
126	occur.
127
128	If, for some reason, the Filter were to disappear the host
129	should fall back on it's initial discovering mechanism - ie.
130	contacting the Filter Manager at it's "well known" location.
131	The host should report that it's lost it's Filter (so the
132	Filter Manager can investigate and remove from it's list of
133	Filters), and then the Filter Manager will reassign a new
134	Filter to the host. Communication can then continue.
135
136	The idea of plugins to the Filters has been introduced.
137	These plugins will implement a predefined plugin interface,
138	and can be chained together at the Filter. Using the
139	interface we can easily add future plugins that can do
140	anything from parsing new data formats, to implementing
141	encryption algorithms. The Filter will pass incoming data to
142	each plugin in turn that it has available, and then finally
143	pass the data on to the Main Filter. The Filter need not
144	have any real knowledge about the content of the data.