OpenSimulator Internals/Connector Architecture

Overview

The connector handles network calls transparently. Calling code does not need to know whether the service is local (standalone) or remote (grid mode) -- the connector abstracts that distinction.

In standalone mode the connector calls the service directly in-process. In grid mode it makes an HTTP call to ROBUST. Same interface either way.

The Five Components

Up to five components are involved in connecting simulator code to a grid service.

Component	Location	Description
Simulator code	OpenSimulator core or a module	Makes the initial service call to get or set data.
Simulator service connector	OpenSim/Region/CoreModules/ServiceConnectorsOut (outbound), ServiceConnectorsIn (inbound)	Two flavours: local (same process, standalone -- calls service directly) and remote (grid mode -- delegates to remote service connector for network call).
Remote service connector	OpenSim/Services/Connectors	Marshals data and makes the network call to the remote service. Not used for in-process connections.
Remote service handler	OpenSim/Server/Handlers	Unpacks the incoming network call and passes it to the service. Not used for in-process connections.
The service	OpenSim/Services/[ServiceName] (e.g. OpenSim/Services/AssetService)	Actually services the call and returns data.

Configuration

Standalone

Connectors and service in the same process:

[Modules]
AssetServices = "LocalAssetServicesConnector"

[AssetService]
LocalServiceModule = "OpenSim.Services.AssetService.dll:AssetService"

Grid

Service runs remotely:

[Modules]
AssetServices = "RemoteAssetServicesConnector"

[AssetService]
AssetServerURI = "http://myassetserver.com:8003"

Example: Asset Get

Note: In OpenSimulator 0.9.2, LocalAssetServiceConnector, RemoteAssetServiceConnector, and HGAssetBroker were replaced by a single module RegionAssetConnector. LocalAssetServiceConnector is still present but only used in tests. The paths below reflect the current architecture.

Standalone path

Simulator calls Scene.AssetService.Get()
Routes to RegionAssetConnector.Get()
Checks cache
On miss, calls AssetService.Get() directly in-process
AssetService retrieves from persistent storage

Grid path

Simulator calls Scene.AssetService.Get()
Routes to RegionAssetConnector.Get()
Delegates to AssetServicesConnector (OpenSim/Services/Connectors)
Makes HTTP GET to http://yourassetserver/assets/assetId
Received by OpenSim/Server/Handlers/Asset/AssetServerConnector
AssetServerGetHandler unpacks request, calls AssetService
Returns asset as XML on success, 404 on miss

HyperGrid path

Simulator calls Scene.AssetService.Get()
Routes to RegionAssetConnector.Get()
RegionAssetConnector determines if asset is local or foreign grid
Foreign: instantiates GridAssetClient for the foreign grid
Makes HTTP GET to foreign asset server
Asset copied to local asset table on retrieval -- same UUID, no link back