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root/i-scream/projects/cms/documentation/minutes/minutes-20001113b.txt
Revision: 1.3
Committed: Wed Nov 15 00:33:45 2000 UTC (23 years, 11 months ago) by ajm
Content type: text/plain
Branch: MAIN
Changes since 1.2: +24 -18 lines
Log Message:
added tdb1's updates and other extras

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 tdb 1.2 [tdb1: Documented by ajm4, comments added by tdb1.]
8    
9 ajm 1.1 This meeting was between ajm4 and tdb1 to discuss and
10     possibly implement parts of the CORE and FilterManager
11     elements of the system.
12    
13    
14    
15     Initial discussion was on the configuration system of the
16     CORE which has been partially completed to date. A key
17     decision that was made was that it will NOT be possible
18     for the elements of the system to update their own
19     configuration, as this will cause difficulties if the user
20     wants to use the file themseleves (ie, add comments). This
21     isn't seen to be a real problem though, as it was only going
22     to be a "funky" extra ;-)
23    
24 tdb 1.2 [tdb1: this will also solve security issues with
25     unauthorised third parties changing settings.]
26    
27    
28 ajm 1.1 Next point was whether or not we would support elements
29 tdb 1.2 being able to be updated without restarting them, ie. a host
30 ajm 1.1 would be able to detect its configuration has changed and
31     adjust accordingly. The method chosen was to use the last
32     modified date stamp of the configuration file as an
33     indicator. When a Configuration object is passed to an
34     element of the system it can determine when the loaded
35     configuration was last edited. The element of the system
36     can then periodically (the period can be set in the
37     configuration ;-) ) ask the Configurator if its
38     configuration has been updated, and act accordingly. The
39     methods:
40    
41 tdb 1.2 long Configuration.getLastModifed() and
42     boolean Configurator.isModified(String conf, long curTime)
43 ajm 1.1
44     where thus implemented and the configurator test class
45     modified to include a test of this system.
46    
47 ajm 1.3 It should also be noted at this stage that a java 'long' is
48     defined as a 'long long' in the IDL->Java mapping.
49 ajm 1.1
50    
51     The next item discussed was the CORBA IDL and general system
52     package structure. It was decided to use the ukc domain as
53     the root identifier for the project. Packages therefore
54     follow the naming:
55    
56     uk.ac.ukc.iscream.<package>.<class>|<sub-package>
57    
58     The IDL and currently implemented classes were updated to
59     refelect this change.
60    
61    
62    
63     The next item to be discussed was the initial thinking and
64     possible implementation of the FilterManager. An initial
65     FilterManager class was fleshed out with hooks to the logger
66     and the configurator, it then creates a FilterListener class
67     which will listen for new Hosts trying to connect to the
68     system. It was NOT decided how Hosts should find the system
69     however a method similar to the WPAD system used to locate
70     web caches was suggested by tdb1.
71    
72     A Host contacts the FilterManager to initialise itself and
73     obtain a host and port number of a Filter that it will talk
74     to. When the FilterListener is contacted by a host it spawns
75     a HostInit object to handle this intialisation. The first
76     thing a Host does is obtain its configuration, this is done
77     by the HostInit object obtaining the configuration of the
78 tdb 1.2 host on its behalf. An initial protocol of how this system
79 ajm 1.3 works is as follows (of course this is subject to later
80     alteration, but seemed like a "good idea at the time"):
81 tdb 1.2
82 ajm 1.1 Host FilterManager.HostInit
83     STARTCONFIG ->
84 tdb 1.2 <- OK | ERROR
85 ajm 1.1 LASTMODIFIED ->
86 tdb 1.2 <- LASTMODIFIED
87 ajm 1.1 DO {
88     PROPERTY ->
89 tdb 1.2 <- VALUE | ERROR
90 ajm 1.1 } UNTIL GOT CONFIG
91    
92     ENDCONFIG ->
93 tdb 1.2 <- OK
94 ajm 1.1
95 ajm 1.3 If there is an ERROR returned after STARTCONFIG, this
96     indicates to the Host that there is no configuration
97     available for it at this time. It may be possible to
98     continue using default values, but this is up to the host
99     configuration. Again, this is not a certain feature and
100     should be discussed with other members of the group.
101    
102 ajm 1.1 If the property section returns an ERROR then this indicates
103     to the host that that property requested doesn't exist, the
104     Host will then deal with this either by ending with an error
105     on the local system or by ignoring it if it can.
106    
107 ajm 1.3 The above features were implemented.
108    
109 tdb 1.2
110 ajm 1.1
111     The next item needed to be developed is an architecture for
112     FilterParent's and FilterChild's, as the next stage of Host
113 ajm 1.3 initialisation is to be passed a 'reference' to a
114     FilterChild. This 'reference' will be a server and a port
115     and not a reference in the CORBA or Java way of thinking.
116 ajm 1.1
117     It was noted that on a "heart beat" with the system, a Host
118     should check to see if its configuration has changed. If it
119     has it should then re-initialise itself. This will allow
120     configuration changes to be made to any part of the system
121     knowing that on the next "heart beat" the configuration will
122     take effect. A point to note about this is that if there is
123     an error in the configuration the Host will simply error and
124     die. What we may want (but still undecided) is a constant
125     retry until the config is ok. So the system administrator
126     will see in the logger destination that there has been an
127     error in this new configuration and can make changes to
128     rectify the problem, without having to interact with the
129     Host program itself.
130    
131    
132    
133     All code generated was placed in the "experimental" tree of
134 ajm 1.3 CVS, awaiting approval from other group members. It should
135     also be noted that although CVS records tdb1 as the
136     'checker inner', it was infact ajm4...as he was the king of
137     code during this meeting ;-p
138 ajm 1.1
139     Many small bug fixes were made to the existing code.
140    
141     It was also noted that there is a need for coding standards.
142    
143     As we had reached an appropriate stage to end, and given the
144 ajm 1.3 late hour, it was decided to conclude the meeting. It was,
145     after all, nearly 7 hours of coding ;-)
146 tdb 1.2
147 ajm 1.3 Since this meeting took place tdb1 has produced Makefiles
148     to allow easy compiling and configuration of the code.
149 tdb 1.2
150 ajm 1.1
151     Meeting was concluded @ 20:45. Next meeting booked for 11:00
152     on Wednesday, until 12:30. Meeting with iau @ 13:30 on that
153     day.