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root/i-scream/projects/cms/documentation/minutes/minutes-20001113b.txt
Revision: 1.4
Committed: Wed Nov 15 00:43:23 2000 UTC (23 years, 4 months ago) by ajm
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Branch: MAIN
Changes since 1.3: +0 -2 lines
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removed a comment I forgot to take out.

File Contents

# User Rev Content
1 ajm 1.1 Minutes of Meeting, 13/11/2000 @ 14:00
2 tdb 1.2 Location: Eliot College, E3E room 8
3 ajm 1.1
4     Present: ajm4, tdb1
5     Absent: none
6    
7     This meeting was between ajm4 and tdb1 to discuss and
8     possibly implement parts of the CORE and FilterManager
9     elements of the system.
10    
11    
12    
13     Initial discussion was on the configuration system of the
14     CORE which has been partially completed to date. A key
15     decision that was made was that it will NOT be possible
16     for the elements of the system to update their own
17     configuration, as this will cause difficulties if the user
18     wants to use the file themseleves (ie, add comments). This
19     isn't seen to be a real problem though, as it was only going
20     to be a "funky" extra ;-)
21    
22 tdb 1.2 [tdb1: this will also solve security issues with
23     unauthorised third parties changing settings.]
24    
25    
26 ajm 1.1 Next point was whether or not we would support elements
27 tdb 1.2 being able to be updated without restarting them, ie. a host
28 ajm 1.1 would be able to detect its configuration has changed and
29     adjust accordingly. The method chosen was to use the last
30     modified date stamp of the configuration file as an
31     indicator. When a Configuration object is passed to an
32     element of the system it can determine when the loaded
33     configuration was last edited. The element of the system
34     can then periodically (the period can be set in the
35     configuration ;-) ) ask the Configurator if its
36     configuration has been updated, and act accordingly. The
37     methods:
38    
39 tdb 1.2 long Configuration.getLastModifed() and
40     boolean Configurator.isModified(String conf, long curTime)
41 ajm 1.1
42     where thus implemented and the configurator test class
43     modified to include a test of this system.
44    
45 ajm 1.3 It should also be noted at this stage that a java 'long' is
46     defined as a 'long long' in the IDL->Java mapping.
47 ajm 1.1
48    
49     The next item discussed was the CORBA IDL and general system
50     package structure. It was decided to use the ukc domain as
51     the root identifier for the project. Packages therefore
52     follow the naming:
53    
54     uk.ac.ukc.iscream.<package>.<class>|<sub-package>
55    
56     The IDL and currently implemented classes were updated to
57     refelect this change.
58    
59    
60    
61     The next item to be discussed was the initial thinking and
62     possible implementation of the FilterManager. An initial
63     FilterManager class was fleshed out with hooks to the logger
64     and the configurator, it then creates a FilterListener class
65     which will listen for new Hosts trying to connect to the
66     system. It was NOT decided how Hosts should find the system
67     however a method similar to the WPAD system used to locate
68     web caches was suggested by tdb1.
69    
70     A Host contacts the FilterManager to initialise itself and
71     obtain a host and port number of a Filter that it will talk
72     to. When the FilterListener is contacted by a host it spawns
73     a HostInit object to handle this intialisation. The first
74     thing a Host does is obtain its configuration, this is done
75     by the HostInit object obtaining the configuration of the
76 tdb 1.2 host on its behalf. An initial protocol of how this system
77 ajm 1.3 works is as follows (of course this is subject to later
78     alteration, but seemed like a "good idea at the time"):
79 tdb 1.2
80 ajm 1.1 Host FilterManager.HostInit
81     STARTCONFIG ->
82 tdb 1.2 <- OK | ERROR
83 ajm 1.1 LASTMODIFIED ->
84 tdb 1.2 <- LASTMODIFIED
85 ajm 1.1 DO {
86     PROPERTY ->
87 tdb 1.2 <- VALUE | ERROR
88 ajm 1.1 } UNTIL GOT CONFIG
89    
90     ENDCONFIG ->
91 tdb 1.2 <- OK
92 ajm 1.1
93 ajm 1.3 If there is an ERROR returned after STARTCONFIG, this
94     indicates to the Host that there is no configuration
95     available for it at this time. It may be possible to
96     continue using default values, but this is up to the host
97     configuration. Again, this is not a certain feature and
98     should be discussed with other members of the group.
99    
100 ajm 1.1 If the property section returns an ERROR then this indicates
101     to the host that that property requested doesn't exist, the
102     Host will then deal with this either by ending with an error
103     on the local system or by ignoring it if it can.
104    
105 ajm 1.3 The above features were implemented.
106    
107 tdb 1.2
108 ajm 1.1
109     The next item needed to be developed is an architecture for
110     FilterParent's and FilterChild's, as the next stage of Host
111 ajm 1.3 initialisation is to be passed a 'reference' to a
112     FilterChild. This 'reference' will be a server and a port
113     and not a reference in the CORBA or Java way of thinking.
114 ajm 1.1
115     It was noted that on a "heart beat" with the system, a Host
116     should check to see if its configuration has changed. If it
117     has it should then re-initialise itself. This will allow
118     configuration changes to be made to any part of the system
119     knowing that on the next "heart beat" the configuration will
120     take effect. A point to note about this is that if there is
121     an error in the configuration the Host will simply error and
122     die. What we may want (but still undecided) is a constant
123     retry until the config is ok. So the system administrator
124     will see in the logger destination that there has been an
125     error in this new configuration and can make changes to
126     rectify the problem, without having to interact with the
127     Host program itself.
128    
129    
130    
131     All code generated was placed in the "experimental" tree of
132 ajm 1.3 CVS, awaiting approval from other group members. It should
133     also be noted that although CVS records tdb1 as the
134     'checker inner', it was infact ajm4...as he was the king of
135     code during this meeting ;-p
136 ajm 1.1
137     Many small bug fixes were made to the existing code.
138    
139     It was also noted that there is a need for coding standards.
140    
141     As we had reached an appropriate stage to end, and given the
142 ajm 1.3 late hour, it was decided to conclude the meeting. It was,
143     after all, nearly 7 hours of coding ;-)
144 tdb 1.2
145 ajm 1.3 Since this meeting took place tdb1 has produced Makefiles
146     to allow easy compiling and configuration of the code.
147 tdb 1.2
148 ajm 1.1
149     Meeting was concluded @ 20:45. Next meeting booked for 11:00
150     on Wednesday, until 12:30. Meeting with iau @ 13:30 on that
151     day.