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0b8aa41 merged virga1 and master
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1 ==========
2 Lantorrent
3 ==========
4
5 Lantorrent is a file distribution protocol integrated into the Nimbus
6 IaaS toolkit. It works as a means to multi-cast virtual machine images
7 to many backend nodes. The protocol is optimized for propagating
8 virtual machine images (typically large files) from a central repository
9 across a LAN to many virtual machine monitor nodes.
10
11 Lantorrent works best for the following scenarios:
12
13 1) large file transfers (VM images are typically measured in gigabytes)
14 2) local area switched network (typical for data center computer racks)
15 3) file recipients are willing peers.
16 4) many endpoints request the same file at roughly the same time
17
18 -----------------
19 Protocol overview
20 -----------------
21
22 When an endpoint wants a file it submits a request to a central agent.
23 This agent aggregates request for files so that they can be sent out in
24 an efficient single multi-cast session. Each request for a source file
25 is stored until either N request on that file have been made or N'
26 seconds have passed since the last request on that source file has been
27 made. This allows for a user to request a single file in several
28 unrelated session yet still have the file transfered in an efficient
29 multi-cast session.
30
31 Once N requests for a given source file have been made or N' seconds
32 have passed the destination set for the source file is determined. A
33 chain of destination endpoints is formed such that each node receives
34 from and sends to one other node. The first node receives from the
35 repository and send to a peer node, that peer node sends to another,
36 and so on until all receive the file. In this way all links of the
37 switch are utilized to send directly to another endpoint in the switch.
38 This results in the most efficient transfer on a LAN switched network.
39
40 Often times in a IaaS system a single network endpoint (VMM) will want
41 multiple copies of the same file. Each file is booted as a virtual
42 machine and that virtual machine will make distinct changes to that file
eb04571 @priteau Fix typo in README
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43 as it runs, thus it needs its own copy of the file. However that file
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44 does not need to be transfered across the network more than once.
45 Lantorrent will send the file to each endpoint once and instruct that
46 endpoint to write it to multiple files if needed.
47
48 -----------------------------
49 Enabling Lantorrent in Nimbus
50 -----------------------------
51
aa6a417 @priteau Improve LANTorrent docs, and sync HTML and README
priteau authored
52 Lan torrent is part of the Nimbus distribution as of Nimbus 2.6.
53 However, due to system administrative overhead it is not enabled by
54 default. To enable Lantorrent in Nimbus there are a few configurations
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55 changes that must be made.
56
aa6a417 @priteau Improve LANTorrent docs, and sync HTML and README
priteau authored
57 The following software is required on both service and VMM nodes:
a0c4bcd updating the doc the show a dependency on py 2.5. There is a problem wi...
BuzzTroll authored
58 - python 2.5
aa6a417 @priteau Improve LANTorrent docs, and sync HTML and README
priteau authored
59 - python simplejson
eed27d2 @priteau Add a note about dependencies
priteau authored
60
aa6a417 @priteau Improve LANTorrent docs, and sync HTML and README
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61 Lantorrent is run out of xinetd thus it must also be installed on all VMMs.
62
63 To install LANTorrent you must take the following steps:
64
65 1) edit $NIMBUS_HOME/nimbus-setup.conf
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66 change lantorrent.enabled: False -> lantorrent.enabled: True
67
aa6a417 @priteau Improve LANTorrent docs, and sync HTML and README
priteau authored
68 2) edit $NIMBUS_HOME/services/etc/nimbus/workspace-service/other/common.conf
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69 change the value of propagate.extraargs:
70 propagate.extraargs=$NIMBUS_HOME/lantorrent/bin/lt-request
71
72 be sure to expand $NIMBUS_HOME to its full and actual path.
73
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74 3) install lantorrent on VMM
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75 - run ./vmm-install.sh on each node
76 either run it as your workspace control user or specify the workspace
77 control user as the first and only argument to the script.
78
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79 4) install lantorrent into xinetd
80 - the vmm-install.sh script creates the file lantorrent. This
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81 file is ready to be copied into /etc/xinetd.d/. Once this is done
82 restart xinetd (/etc/init.d/xinetd restart).
83
495ba90 lantorrent patches so it will work with older versions of python
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84 5) change the propagation method.
85 - edit the file:
86 $NIMBUS_HOME/services/etc/nimbus/workspace-service/other/authz-callout-ACTIVE.xml
87
88 and change:
89 <property name="repoScheme" value="scp" />
90 to:
91 <property name="repoScheme" value="lantorrent" />
92
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93 6) restart the service: $NIMBUS_HOME/bin/nimbusctl restart
94
95 7) [optional] if the path to Nimbus on the workspace control nodes (VMMs)
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96 is not /opt/nimbus you will also need to edit a configuration file on
97 all backends.
98
99 In the file:
100 <workspace control path>/control/etc/workspace-control/propagation.conf
101
102 make sure the value of:
103
104 lantorrentexe: /opt/nimbus/bin/ltclient.sh
105
3eb657a @priteau Fix typo
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106 points to the proper location of you ltclient.sh script. This should
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107 be a simple matter of changing /opt/nimbus to the path where you chose
108 to install workspace control.
109
110 ----------------
111 Protocol details
112 ----------------
113
114 requests
115 --------
116
117 transfer
118 --------
119
120 A transfer from one peer to another is performed for forming a TCP
121 connection. A json header is first sent down the socket describing the
122 transfer. It describes the files where data must be written, and the
123 other endpoints where the data must be sent. As data comes in the
124 server will store it to one or more files and forward it on to another
125 endpoint. All of this information is contained in the header. The
126 header has the following format:
127
128 {
129 host
130 port
131 length
132 requests = [ {filename, id, rename}, ]
133 destinations =
134 [ {
135 host
136 port
137 requests = [ { filename, id, rename } ]
138 block_size
139 }, ]
140 }
141
142 When the server forms a connection with the next endpoint it will form
143 another header by removing the first entry of the destination list and
144 using the values contained in it as root level values in the header
145 described above. If the destination list is empty then the server is the
146 last in the chain and no forwarding is needed.
147
148 After the header is sent the binary payload (the contents of the file)
149 is sent down the socket.
150
151 The 'requests' value of the json header contains destination
152 information. Each filename in the list is a file where data should be
153 written. The value of id is the id of the request for that file. The
154 value of rename is a boolean which determines if the file should be
155 first written to a temporary location and then moved to the final
156 location once all of the data is received. This feature is helpful in
157 monitoring file completion.
158
159 security
160 --------
161
162 Each connection to a lantorrent peer comes with a json header. Directly
163 following that header is a line of text in the following format:
164 EOH : <signature>
165
166 The value of signature is the hmac signature of everything that came
167 before the literal EOH. The password for that signature is found in the
168 lt.ini file. Every endpoint and the master repo must have the same
169 value for that password.
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