The OceanStore Project OceanStore HelloWorld HOWTO by Hakim Weatherspoon, Chiu Wah Kelvin So, and Jason Lee

Step 3: Finding the Three Closest Servers

Goal

A client to send a message to more than one of the closest servers. The servers have to be unique. Then servers print out the messages, "Hello! How are you" and send a response "Great! The weather is wonderful today!" The client prints out the response. After all the responses have been received, client exits.

Directions

• Protocol:
  • All 10 HelloWorldServers publish DDPublishReq
  • The HelloWorldClient gathers information of virutual coordinate of any 7 different HelloWorldServer by sending a HelloWorldLocateMsg.
  • HelloWorldClient listens for HelloWorldLocateMsg which includes the information of the 7 HelloWorldServer. Send a VivaldiRequestVC to find out the local virutal coordinate.
  • HelloWorldClient listens for VivaldiReplyVC. Using local virutal coordinate in the VivaldiReplyVC, HelloWorldClient calculates the closest 3 HelloWorldServer, and sends them message using HelloWorldRouteMsg.
  • The 3 HelloWorldServers which have received a HelloWorldRouteMsg prints out the message and send back a response to HelloWorldClient using HelloWorldRouteMsg.
  • The HelloWorldClient listens for HelloWorldRouteMsg and prints out the message. After receving HelloWorldRouteMsg from 3 different HelloWorldServer, HelloWorldClient exits.

• For Step 3, there are only 5 files that needed to be modified
  • HelloWorldQueryState
  • HelloWorldQuery
  • HelloWorldClient
  • HelloWorldServer
  • HelloWorldLocateMsg
    
• HelloWorldLocateMsg
  • use HelloWorldLocateMsg to gather servers information by setting input forward to false. (Note: by setting forward to false, HelloWorldLocateMsg will not be forward to any of the HelloWorldServer. After HelloWorldLocateMsg is stopped by DDQueryResultMatch, HelloWorldLocateMsg returns to HelloWorldClient and gathered information would be stored in HelloWorldQueryState.)
    
• HelloWorldQueryState
  • constructor take in one input: number of servers that needed to be gathered information on
  • use a data structure map to keep track of the servers guid and virtual coordinates.
  • 4 methods:
    • void add(SecureHash src, VirtualCoordinate vc) - insert src and vc into the map
    • int numberOfRequestServers() - return the number of the input from the constructor
    • int size() - the current size of the set data structue
    • Map getMap() - return the map which contains the information
• HelloWorldQuery
  • Only need to modified the query method
  • bp_guid in the query method is the pointer to one of the servers, and bp_hinfo.coordinate is the virtual coordinate of the server
    
• HelloWorldClient
  • HelloWorldQueryState in HelloWorldLocateMsg has all the gathered information of the servers
  • Use bamboo.vivaldi.VivaldiReplyVC and bamboo.vivaldi.VivaldiRequestVC to find the local virtual coordinate.
  • local virtual coordinate is in VivaldiReplyVC.coordinate.
  • To calculate the differences in distance, use localVirtualCoordinate.distance(destinationVirtualCoordinate).
  • Send HelloWorldRouteMsg to the 3 closest HelloWorldServers.
    
• Example:
  • VivaldiReplyVC and VivaldiRequestVC: dd.host.impl.HostHb
  • VirtualCoordinate.distance(destinationVC): dd.ptr.impl.PtrMgr

Experiment file setting

• add another field NumOfClosestServers to HelloWorldClient3.stg
• add 10 servers and call them HelloWorldServers0 - HelloWorldServers9
• add 1 client
• set *.HostHb.AlarmTimeout 20000 to start up the virtual coordinate setup earlier
• also set HelloWorldClient.StartTime later