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Contents of /projects/cms/documentation/minutes/minutes-20001113b.txt

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Wed Nov 15 02:05:53 2000 UTC (18 years, 8 months ago) by tdb
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Added a quick bit about configuration file names.

1 Minutes of Meeting, 13/11/2000 @ 14:00
2 Location: Eliot College, E3E room 8
4 Present: ajm4, tdb1
5 Absent: none
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.
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 ;-)
22 [tdb1: this will also solve security issues with
23 unauthorised third parties changing settings.]
25 A standard has almost be devised for filenames of
26 configuration files. As it stands all hostname properties
27 will be get in a file with the following name;
29 hostname.domain.properties
31 nb. This will always be *lower case*. This is important as
32 some hosts (eg. stuE...) have mixed case, so having all
33 lower case saves confusion.
35 However, any other config files (such as the filterManager)
36 can have any name in any case. The file itself will be of
37 the name format;
39 name.properties
41 So in the case of the filterManager this would be
42 "filterManager.properties".
44 A standard should be defined here for concistency.
46 Next point was whether or not we would support elements
47 being able to be updated without restarting them, ie. a host
48 would be able to detect its configuration has changed and
49 adjust accordingly. The method chosen was to use the last
50 modified date stamp of the configuration file as an
51 indicator. When a Configuration object is passed to an
52 element of the system it can determine when the loaded
53 configuration was last edited. The element of the system
54 can then periodically (the period can be set in the
55 configuration ;-) ) ask the Configurator if its
56 configuration has been updated, and act accordingly. The
57 methods:
59 long Configuration.getLastModifed() and
60 boolean Configurator.isModified(String conf, long curTime)
62 where thus implemented and the configurator test class
63 modified to include a test of this system.
65 It should also be noted at this stage that a java 'long' is
66 defined as a 'long long' in the IDL->Java mapping.
69 The next item discussed was the CORBA IDL and general system
70 package structure. It was decided to use the ukc domain as
71 the root identifier for the project. Packages therefore
72 follow the naming:
74 uk.ac.ukc.iscream.<package>.<class>|<sub-package>
76 The IDL and currently implemented classes were updated to
77 refelect this change.
81 The next item to be discussed was the initial thinking and
82 possible implementation of the FilterManager. An initial
83 FilterManager class was fleshed out with hooks to the logger
84 and the configurator, it then creates a FilterListener class
85 which will listen for new Hosts trying to connect to the
86 system. It was NOT decided how Hosts should find the system
87 however a method similar to the WPAD system used to locate
88 web caches was suggested by tdb1.
90 A Host contacts the FilterManager to initialise itself and
91 obtain a host and port number of a Filter that it will talk
92 to. When the FilterListener is contacted by a host it spawns
93 a HostInit object to handle this intialisation. The first
94 thing a Host does is obtain its configuration, this is done
95 by the HostInit object obtaining the configuration of the
96 host on its behalf. An initial protocol of how this system
97 works is as follows (of course this is subject to later
98 alteration, but seemed like a "good idea at the time"):
100 Host FilterManager.HostInit
102 <- OK | ERROR
105 DO {
107 <- VALUE | ERROR
111 <- OK
113 If there is an ERROR returned after STARTCONFIG, this
114 indicates to the Host that there is no configuration
115 available for it at this time. It may be possible to
116 continue using default values, but this is up to the host
117 configuration. Again, this is not a certain feature and
118 should be discussed with other members of the group.
120 If the property section returns an ERROR then this indicates
121 to the host that that property requested doesn't exist, the
122 Host will then deal with this either by ending with an error
123 on the local system or by ignoring it if it can.
125 The above features were implemented.
129 The next item needed to be developed is an architecture for
130 FilterParent's and FilterChild's, as the next stage of Host
131 initialisation is to be passed a 'reference' to a
132 FilterChild. This 'reference' will be a server and a port
133 and not a reference in the CORBA or Java way of thinking.
135 It was noted that on a "heart beat" with the system, a Host
136 should check to see if its configuration has changed. If it
137 has it should then re-initialise itself. This will allow
138 configuration changes to be made to any part of the system
139 knowing that on the next "heart beat" the configuration will
140 take effect. A point to note about this is that if there is
141 an error in the configuration the Host will simply error and
142 die. What we may want (but still undecided) is a constant
143 retry until the config is ok. So the system administrator
144 will see in the logger destination that there has been an
145 error in this new configuration and can make changes to
146 rectify the problem, without having to interact with the
147 Host program itself.
151 All code generated was placed in the "experimental" tree of
152 CVS, awaiting approval from other group members. It should
153 also be noted that although CVS records tdb1 as the
154 'checker inner', it was infact ajm4...as he was the king of
155 code during this meeting ;-p
157 Many small bug fixes were made to the existing code.
159 It was also noted that there is a need for coding standards.
161 As we had reached an appropriate stage to end, and given the
162 late hour, it was decided to conclude the meeting. It was,
163 after all, nearly 7 hours of coding ;-)
165 Since this meeting took place tdb1 has produced Makefiles
166 to allow easy compiling and configuration of the code.
169 Meeting was concluded @ 20:45. Next meeting booked for 11:00
170 on Wednesday, until 12:30. Meeting with iau @ 13:30 on that
171 day.

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