Core ConceptsAdvanced

Three-Service Dependency Chain

DataService, InventoryService, and ShopService a real dependency graph and the OwlInit order it guarantees.

DependenciesOwlInitTopological Sort

ServerScriptService/Services/DataService.lua

local DataService = Owl.CreateService({
    Name = "DataService",
    Dependencies = {},
})
 
function DataService:OwlInit()
    print("[DataService] Ready.")
end
 
function DataService:OwlStart()
end
 
return DataService

ServerScriptService/Services/InventoryService.lua

local InventoryService = Owl.CreateService({
    Name = "InventoryService",
    Dependencies = { "DataService" },
})
 
function InventoryService:OwlInit()
    self.DataService = self.GetService("DataService")
    print("[InventoryService] Ready, DataService was already initialized.")
end
 
function InventoryService:OwlStart()
end
 
return InventoryService

ServerScriptService/Services/ShopService.lua

local ShopService = Owl.CreateService({
    Name = "ShopService",
    Dependencies = { "DataService", "InventoryService" },
})
 
function ShopService:OwlInit()
    self.DataService = self.GetService("DataService")
    self.InventoryService = self.GetService("InventoryService")
    print("[ShopService] Ready, both dependencies were already initialized.")
end
 
function ShopService:OwlStart()
end
 
return ShopService

What's happening here

Owl computes a topological sort from these three Dependencies tables the OwlInit order is always DataService, then InventoryService, then ShopService.
Even though ShopService lists two dependencies, Owl only guarantees THIS Service's own dependencies finished first not a global order across every unrelated Service.
Removing "DataService" from ShopService.Dependencies while still calling self.GetService("DataService") in OwlInit would keep working most of the time until a load-order change makes it fail intermittently, exactly the bug class this graph exists to prevent.

Related docs

Dependencies Lifecycle

PreviousPlayer Profiles with OwlData