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changes.mady.by.user Bruce Schuchardt

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Once the coordinator's ID is known the new member sends a JoinRequest to it.  The new member will know that it has been accepted when it receives a membership view containing its ID.  At this point it sets the view-ID of its identifiers.  The view-ID, in combination with its IP address and membership port (the UDP port used by JGroups) uniquely identifies this member.

 

PlantUML
title state transitions for joining member
[*] -> Discovery
Discovery: search for coordinator
Discovery: using Locator service
Discovery -> Joining
Joining: join req sent to coordinator
Joining -> Member
Member: unique ID established
Member: membership view installed
Member -> [*]
 

Simultaneous joins and leaves

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PlantUML
title
Details of concurrent startup of two locators when the
locators are preferred as membership coordinators.  This
diagram focuses on the second locator, L2
end title
hide footbox

entity L1 #grey
entity C
entity L2

note right of L2
L1 and L2 have been killed.  C
detects loss and becomes coordinator.
L1 and L2 are restarted simultaneously
end note

L1 -> C : JoinRequest
C -> L1 : prepare/install view(coord=C,L1)

L2 -> L1 : recover
L1 --> L2 : old view + L1
note right of L2
L2 will try to join with L1 and then
fall into findCoordinatorFromView
end note

L2 -> L1 : JoinRequest
L1 -> L1 : queues JoinRequest from L2

C -> L1 : install view(coord=C,L1)
note left: L1 is a member now

L2 -> C : FindCoordinator
note right: (sent via UDP)
C --> L2 : response(coord=C)
note right
At this time C is still coordinator and
will tell L2, who will try to join with it
end note

L1 -> C : prepare/install view(coord=L1,C)

L2 -> C : JoinRequest
C --> L2 : JoinResponse(coord=L1)
note right
C has received the deposing view from L1
and will respond to L2's JoinRequest with
a response telling it that L1 is now coordinator
end note

L2 -> L2 : waits for response to initial JoinRequest 
L1 --> L2 : prepare/install view(coord=L1,C,L2)
L2 -> L2 : continues startup
 

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