Distributed Shared Memory on Ericsson Labs

Distributed

Shared

Memory

A labs.ericsson.com APIhttp://labs.ericsson.com/apis/distributed-shared-memory/

© Ericsson AB 2010 | Page 2

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Distributed shared memory

› Distributed Shared Memory enables a distributed in-memory database for JavaScript applications

– Get a replica of a DSM storage with a specified address from a DSM server

– Register a listener and be notified when data is changes by other users

– Modify data locally and synchronize changes in the background with other replicas

› Merge conflicts are automatically resolved

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Why distributed shared memory?

› Let web developers focus on developing highly interactive and responsive web-based collaboration software without having to deal with complicated issues such as – networking protocols

– database management

– concurrency control

› Also, using a local replica where data can be modified directly without a lock or blocking improves user experience

› Synchronizing application states among multiple clients

› Implement group-wares or collaborative web services supporting simultaneous real-time interactions

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Main Features

› Makes it possible for multiple JavaScript clients to address andmanipulate the same data at the same

› Plain JavaScript Lib (no browser plug-in required)

› High performance and low delay

› Optimistic replication to resolve merge conflicts

› Event-driven (register a listener and be notified when data change)

› Support for both ordered arrays/lists and unordered key-value hash tables

› Support for both persistent storage (disk) and transient data (RAM)

› Automatic garbage collection

› Time-to-live (specify how long time a value should be stored)

› Possibility to link DSM storages to build graph databases

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Use cases

Examples of usage

› E-learning

› Tele-care, e.g. remote health care and specialist consultation, remote monitoring etc.

› Call center support

› Collaborative work, e.g. a shared whiteboard or other collaborative editing systems etc.

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› All clients (and servers) DSM SW contains predefined rules how to resolve conflicts

“Adjust” or transform

incoming operation to

match local changes

Merge conflicts are resolved

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// get a replica of hash://simpleTest

var hash = memCtrl.get(“hash://simpleTest”);

// update the web page when the replica is cloned

hash.onReady = function () {

document.getElementById(“myTextfield”).value = hash.get(“myKey”);

};

// handle changes to the replica

hash.onUpdate = function (op) {

document.getElementById(“myTextfield”).value = op.value;

};

// update the local replica

hash.set(“myKey”, “myValue”);

// send the operation to all other replica clients in the background

hash.submit();

JavaScript API

› Simple and easy to use to API

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Example applications

Collaborative WorkspacesShared Whiteboards

Shared JavaScript Apps, e.g. a Shared Map Widget

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