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Platform Team/Sugar Network/Architecture (view source)

Revision as of 23:42, 26 November 2012

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See also the [[Sugar_Network|introduction page]] and the [[Sugar_Network/Concept|basic concepts overview]].
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This is a twin page of Sugar Network's [[Sugar_Network/Concept|basic concepts]] from technical point of view. See also the [[Sugar_Network|introduction page]].
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== Summary ==
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== Overview ==
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The technical decisions are tailored by:
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=== Functioning ===
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* Real needs of deployments like [[Deployment_Team/Peru/Puno#The_problem|one-teacher schools in Peru]] and should be as simple as possible;
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The only worfklow within the Sugar Network from the technical point of view is:
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* The system, from users point of view, should just work proving high-level services that cover the full collaboration circle that should exist within Sugar learning community;
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* The system should be useful not only for off-line environments, but also for cases in decent Internet connection.
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== Overview ==
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* Clients create, modify and browse different types of resources ([[Sugar_Network/Concept#Resources|resources]] from conceptual point of view, [[Platform_Team/Sugar_Network/API#Resources|resources]] from the API point of view) on a server;
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* If this server is a [[#Node_servers|Node]] server, the system will take care about [[#Synchronization|synchronizing]] its resources with other Node servers and, finally, with the central one, the [[#Master_server|Master]] server.
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[[File:Sugar-networks-architecture.png|right]]
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=== Components ===
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The Sugar Network consists of different types of components:
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This is technical view on [[Sugar_Network/Concept#Overview|three levels]] of the Sugar Network:
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* [[#Server|Server side]] that provide [[Sugar_Network/API|API]] for clients:
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* [[#Server|Server side]],
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** [[#Mothersip|Mothersip]] server that keeps the whole Sugar Network information, clients might connect directly to this server (on-line case) or indirectly via distributed servers (off-line case);
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* [[#Conceptual_level|Conceptual level]],
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** Optional [[#Distributed_servers|distributed servers]], contain a [[#Synchronisation|synchronised]] copy of central server (might be not for the entire Network to save storage space);
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* [[#Client|Client side]].
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* [[#Client|Client side]]:
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** Client application that uses [[Sugar_Network/API|API]] to interact with a server;
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** Client application that [[#Personal_server|provides]] limited [[Sugar_Network/API|API]] to support server-less workflow.
      
== Server ==
 
== Server ==
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In all cases the server [[Sugar_Network/API|API]] is the same for clients. But depending on connectivity, clients might be connected to the [[#Mothership|Mothership]] or to an [[#Distributed_servers|intermediate server]].
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[[File:Sugar-networks-architecture.png|right]]
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Server side is represented by:
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=== Mothership ===
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* [[#Master_server|Master]] server that keeps the whole Sugar Network information, clients might connect directly to this server (on-line case) or indirectly via Node servers (off-line case);
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* Optional [[#Node_servers|Node]] servers, contain a [[#Synchronization|synchronised]] copy of central server (might be not for the entire Network to save storage space);
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The place where data is being collected from all distributed server. If clients have connectivity, they can connect to the Mothership to contribute to the Network directly.
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In all cases the server [[Platform_Team/Sugar_Network/API|API]] is the same for clients. But depending on connectivity, clients might be connected to the [[#Master_server|Master]] server or to a [[#Node_servers|intermediate server]].
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=== Distributed servers ===
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=== Master server ===
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The place where data is being collected from all Node servers. If clients have connectivity, they can connect to the Master to contribute to the Network directly.
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=== Node servers ===
    
Servers that will be useful if:
 
Servers that will be useful if:
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* connectivity is not cheap and its usage needs to be minimized.
 
* connectivity is not cheap and its usage needs to be minimized.
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Distributed services provide full featured [[Sugar_Network/API|API]] as the Mothership does. Distributed servers need to be [[#Synchronisation|synchronized]].
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Node servers provide full featured [[Platform_Team/Sugar_Network/API|API]] as the Master does. Nodes need to be [[#Synchronization|synchronized]].
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== Conceptual level ==
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This is how Sugar Network looks like on [[Sugar_Network/Concept|conceptual level]] represented by the [[Platform_Team/Sugar_Network/API|API]].
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=== Objects model ===
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{{:Platform_Team/Sugar_Network/Objects_model}}
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The model refers to the following additional information:
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=== Synchronisation ===
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=== Simplified editing workflow ===
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To let Network participant, connected to particular [[#Distributed_servers|distributed server]], interact with people from another distributed servers or with people from the Internet, distributed servers need to be synchronized.
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The system is designed to be as lightweight as possible to make it running on XO laptops in unmaintainable environments and simplify synchronization. So, the following design decisions were taken:
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Server might be synchronised:
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* No history for Sugar Network objects, only events about made changes;
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* Only object author(s) can process editing;
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* But, other people can suggest changes (that might be implemented on client side in pretty powerful way, e.g., people can change objects but it will be postponed for later author(s)' review).
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* With the Mothership, if connectivity presents;
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That might be changed but only after making system one level more complicated.
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* With the Mothership or any other distributed servers via the [[Wikipedia:Sneakernet|Sneakernet]].
      
== Client ==
 
== Client ==
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This is what Network participants are interacting with. This is a software that let people get access to the Sugar Network and define how Sugar Network should look like from users point of view. User experience, that these clients provide, might be too different from a client to a client. Starting from a couple of elements in the already existing software's [[Wikipedia:Graphical_user_interface|GUI]] (when people even don't suspect they are interacting with the Sugar Network) and ending with clients that represent conceptual level as close as possible.
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Client side is represented by:
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* Client application that uses [[Platform_Team/Sugar_Network/API|API]] to interact with a server;
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* Client application that [[#Personal_server|provides]] limited [[Platform_Team/Sugar_Network/API|API]] to support server-less workflow.
    
Client application is local, for reasons:
 
Client application is local, for reasons:
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* Originally, Sugar Network was being developed for deployments where teachers' XOs will be distributed servers, thus, it will be useful to delegate some of computing to students' XOs;
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* Originally, Sugar Network was being developed for deployments where teachers' XOs will be Node servers, thus, it will be useful to delegate some of computing to students' XOs;
 
* Stimulate doing behaviour when it should be possible to create new client application or tweak existing on a client side;
 
* Stimulate doing behaviour when it should be possible to create new client application or tweak existing on a client side;
 
* It is all time possible to create Web application on a server side.
 
* It is all time possible to create Web application on a server side.
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=== Default client ===
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=== Personal server ===
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The default client is implemented using Web technologies to:
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This local application provides limited [[Platform_Team/Sugar_Network/API|API]] to get access to:
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* Using Web technologies might make client developing easier;
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* Private data in user's home directory,
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* Make it possible to reuse Sugar Network in any Web browser in any Desktop Environment, i.e., not only from Sugar Shell;
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* Data accessible from removable devices like USB sticks or SD cards.
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* It might be easier to find potential Sugar contributors within Web developers rather than developers who know GTK.
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It might sound a bit confusing to have local Web application, but this decision is based on:
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== Synchronization ==
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* Local Web applications serve only one user and are much simpler than singular applications that are intended to serve multiple users simultaneously;
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To let Network participant, connected to particular [[#Node_servers|Node server]], interact with people from another Node servers or with people from the Internet (Master server), Node servers need to be synchronized.
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* It might be useful to design simple and clean code using existing Web technics like MVC;
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* Thus, it will be easier for doers to learn, change, reimplement the new clients.
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=== Personal server ===
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Server might be synchronized:
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* With the Master, if connectivity presents;
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* With the Master or any other Node servers via the [[Wikipedia:Sneakernet|Sneakernet]].
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This local application provides limited [[Sugar_Network/API|API]] to get access to:
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== Getting involved ==
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* Private data in user's home directory,
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{{:Sugar_Network/Feedback}}
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* Data accessible from removable devices like USB sticks or SD cards.
      
== References ==
 
== References ==
    
* An [http://wiki.laptop.org/go/Sneakernet OLPC wiki page] about the [[Wikipedia:Sneakernet|Sneakernet]].
 
* An [http://wiki.laptop.org/go/Sneakernet OLPC wiki page] about the [[Wikipedia:Sneakernet|Sneakernet]].
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