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Distribution of Data and Remote Invocation of
Programs
Tomasz Müldner, Zhonghai Luo and Elhadi Shakshuki* Jodrey School of Computer Science, Acadia University,
Wolfville, NS, Canada
* presenting
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Contents of the Talk
• General goals for systems that implement data distribution and remote program invocation
• Distributed Installer, DI
• Related products
• Conclusions
• Future Work
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General Goals
• Platform Independence• Security• Scalability• Pull and Push• Efficiency• Synchronization• Fault Tolerance• Flexibility• Selective Choice• Remote Invocation
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DI: Data Distribution
• Two kinds of applications:– subscriber expresses interest in some data
that can be provided by a publisher– publisher selects subscribers and specifies
data to be sent to these subscribers.
• A single application may be at the same time both, a publisher and a subscriber
• SSL is used to support secure transmission
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DI: Channel
• An abstract concept that represents a virtual, unidirectional connection between two nodes
(similar to a pipe used in P2P systems). • Two kinds of channels:
– P-channel, created by a publisher.– S-channel, created by a subscriber.
• Each channel has– name– optional description
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DI: P-channel
Each channel specifies the source of its data, i.e. the directory in the file system on the publisher’s computer.
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DI: P-channel
• the publisher can push, or distribute some or all of P-channels to one or more selected subscribers
• when the subscriber receives the incoming P-channel, it will automatically create the corresponding S-channel based on– publisher's IP and port number– the name of the P-channel.
• any data in the P-channel will be pushed into the newly created S-channel.
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Publisher’s Configuration Files
• publisher.properties (static)– port number on which the publisher will send
data;– a root directory for storing all channels’
description;– the filename and password for the keystore
used to establish secure SSL communication path;
• target.properties (static)– lists all potential subscribers.
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Subscriber’s Configuration Files
• subscriber.properties– port number for receiving data;– a root directory for storing all incoming channels’ data;– a channel creation type– the filename and password for the keystore used to
establish secure SSL communication path;– a security flag indicating whether or not the data
transmission is secure (true by default);– a channel update type– a channel update option
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Relative Virtual Mapping
Example:1. A publisher P creates a channel "quote", and specifies
the corresponding directory "c:\program\quote".2. A publisher distributes the "quote" channel to a
subscriber S with all channel data (it will include all files and sub-directories under "c:\program\quote").
3. In S, a channel named "quote" is automatically created, and all received data (files and sub-directories) are stored with the original hierarchy under the root channel directory(specified in the configuration file subscriber.properties)
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S-channel
• the S-channel is the reference to the corresponding P-channel
• typically created automatically by subscriber software when receiving incoming P-channels pushed by publishers
• the subscriber can also manually create an S-channel:
• the subscriber must know in advance the available channel names in publisher side
• if the channel name specified in S-channel does not exist in publisher side, this S-channel is invalid, just like that you set wrong frequency for a TV station channel.
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S-channel
GUI with buttons to create, modify, delete S-channels, and update the selected S-channel, i.e. pull data for this channel from specified publisher side.
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New S-channel
•An address of the publisher node
• channel name
• description,
• update type and option (they can also be used for an existing S-channel, this way, the subscriber can control the way data are received)
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Remote Invocation
To distribute and to invoke components C1, C2, C3:1. A publisher (on N) creates three channels; one for each
of N1, N2 and N3.2. The publisher specifies the Main class in the descriptor
file app.xml file (explained in the next slide) for each channel.
3. The publisher adds addresses of N1, N2 and N3 to the file target.properties.
4. The publisher distributes all channels to three subscribers
5. The publisher uses the "remote start" button
Components: C1 C2 C3Machine N
Machine N1 Machine N2 Machine N3
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XML-based Descriptor
Defines the startup class for the distributed program and the necessary path information to load dependent classes for this program, for example:
<?xml version="1.0" encoding="ISO-8859-1"?><App name="CS Lab course"><MainClass> ca.acadiau.cs.Lab </MainClass><ClassPath> client.jar </ClassPath></App>Should be located in the channel and sent to the subscriber
along with other channel’s content.
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Related Work
• UNISON, a file-synchronization tool• Idem, a File Synchronization and Folder
Replication utility • SFTP Plugin for Eclipse, provides file and
directory synchronization• DI, a platform independent system that:
– uses SSL to support security– supports both; push and pull model, – one to one and one to many synchronization, with
selective choice of files and directories. – provides a limited form of remote program invocation.
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Conclusion
DI satisfies goals for applications that implement remote file synchronization
and remote program invocation