@startuml
'https://plantuml.com/sequence-diagram

participant Matchmaker
participant Agones

participant "Canary Fleet\nResource" as CanaryFleet
participant "Stable Fleet\nResource" as StableFleet

Matchmaker -> Agones: Create: <i>GameServerAllocation</i>
note left
  <i>GameServerAllocation</i> is implemented to prefer
  allocating from the Canary <i>Fleet</i>, but if a Ready
  <i>GameServer</i> cannot be found in the Canary Fleet,
  to fall back to the Stable <i>Fleet</i>.
end note

group GameServerAllocation
else Check Canary Fleet first
Agones -> CanaryFleet: Check if <i>GameServer<i> is available
note right
  The Canary <i>Fleet</i> is
  usually a small, fixed size
end note
else None available in Canary Fleet
Agones -> StableFleet: Check if <i>GameServer<i> is available
note right
  When the Canary <i>Fleet</i> is fully allocated, the
  allocation falls over to the Stable <i>Fleet</i>.
end note
end group

Matchmaker <-- Agones: returns <i>Allocated GameServer</i> record

@enduml