Transcript SPREAD TOOLKIT

SPREAD TOOLKIT
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High performance messaging middleware
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Presented by
Sayantam Dey
Vipin Mehta
What is SPREAD?
Spread is a group communication system that
provides a number of messaging services to
applications. These services can then be used
by applications to make it easy to write fullfeatured reliable groupware, distributed
servers, client-server applications, chat and
news services, and many other networked
enabled tools.
SPREAD – How it works
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SPREAD is composed of 2 entities – daemons
and client processes.
Daemon(s) maintain information about all
processes connected to it and the presence of
other daemon(s), if any.
Client processes join/leave the group or
send/receive messages using the SPREAD
primitives.
Basic Services
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Abstraction of a group – a name represents a set of
processes, all of whom receive messages sent to the
group.
Multicast of messages to a group.
Membership.
Reliable message delivery.
Ordering of messages sent to a group.
Failure detection of members of group.
A strong semantic model of how messages are
handled in response to group changes.
SPREAD primitives
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SP_connect(): Initial call an application must make to establish a
connection with a Spread daemon.
SP_disconnect(): Called when the application is finished with a
connection to the Spread daemon.
SP_join(): Joins a group with the name passed as the string
group. If the group does not exist among the Spread daemons it is
created, otherwise the existing group with that name is joined.
SP_leave(): Leaves a group with the name passed as the string
group.
SP_multicast and family: SP multicast and its variants all can send
a message to one or more groups.
SP_receive and SP_scat_receive: This receives data and
membership messages.
Other functions for error reporting.
SPREAD architecture
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Modular Design. Divided into 2 components –
implementation of the network communication layer
and multiple client interfaces.
Multiple link protocols supported in the network
communication layer. Currently implements 3.
Ring Protocol: for low latency LANs with not more than
30 daemons.
Point to Point: stable transport over WAN.
Hop: cross WAN with high latency and loss.
Interfaces implemented in C, Perl and Java.
SPREAD guarantees
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Native support of Extended Virtual Synchrony (EVS).
Can detect network partition. Generates a ‘NETWORK’
event, which allows client processes to obtain the
updated membership view.
Provides a ‘Level of Service’.
This value determines the extent of ordering and
reliability of the message. The application can choose
different levels for each message.
5 different levels of service implemented.
SPREAD guarantees continued…
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This table shows the different levels of service and their
relationship with ordering and reliability. (from the SPREAD
toolkit user’s guide)
SPREAD application areas
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Replicated servers
Generic message bus for clusters and
distributed clusters
N-way fail-over for IP addresses
Collaborative tools – share data, video and
audio conferencing
Distributed Shared Memory
Why use SPREAD
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Powerful, but simple API. Only six basic calls are required to
utilize Spread.
Spread is optimized and can handle over 8,000 1Kbytes
messages a second in local area network settings.
Spread allows unicast, multicast, multi-group multicast, scattergather calls, and multiple query functions.
Flexible message semantics: Spread supports all levels of
messaging from unreliable to agreed (also known as total order) to
safe (which guarantees all daemons receive the message before
any deliver it to applications), and provides complete extended
virtual synchrony.
Why use SPREAD continued…
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Spread handles network and machine partitions and
re-merges safely and notifies applications about the
current state of the group.
Cross Platform: Spread supports cross-platform
operation between Unix (BSD, Linux, Solaris, Irix, AIX,
Mac OS X, etc.) and Windows (2000/NT/98/95).
Spread currently has programming API's for C/C++,
C#, Java, Perl, Python and Ruby.
References
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www.spread.org
www.cnds.jhu.edu
SPREAD user guide
The Spread Wide Area Group Communication
System, Yair Amir and Jonathan Stanton.