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= OpenSimulator Internals/Connector Architecture/Simulation Connector =

== Overview ==

SimulationServiceConnector is the remote connector for ISimulationService. It handles inter-simulator communication: creating and updating agents during teleport and region crossing, and transferring objects between regions. Unlike the other connectors, it talks directly to region simulators, not to ROBUST.

Source file:

OpenSim/Services/Connectors/Simulation/SimulationServiceConnector.cs

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=== Initialisation ===

No config file reading. No service URI -- the destination URI comes from GridRegion.ServerURI on each call.

Two constructors:
* Default (no args)
* IConfigSource -- no-op, config argument unused

GetScene() and GetInnerService() always return null.

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=== Transport ===

Unlike all other connectors, SimulationServiceConnector does not use SynchronousRestFormsRequester. It uses WebUtil methods with OSDMap (LLSD) payloads:

* WebUtil.PostToServiceCompressed() -- compressed POST, used for CreateAgent first attempt
* WebUtil.PostToService() -- uncompressed POST, used as fallback
* WebUtil.PutToServiceCompressed() / PutToService() -- PUT, used for UpdateAgent
* WebUtil.ServiceOSDRequest() -- used for QueryAccess (QUERYACCESS method), ReleaseAgent and CloseAgent (DELETE)

URL pattern: destination.ServerURI + "agent/" + agentID + "/"

AgentPath() and ObjectPath() are virtual -- subclasses can override the path segments.

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=== Agent Methods ===

==== CreateAgent() ====

public bool CreateAgent(GridRegion source, GridRegion destination, AgentCircuitData aCircuit, uint flags, EntityTransferContext ctx, out string reason)

# Packs AgentCircuitData via aCircuit.PackAgentCircuitData(ctx)
# Adds context, source region info, destination region info, and teleport flags via PackData()
# Attempts compressed POST first (WebUtil.PostToServiceCompressed)
# On success: reads _Result map for actual success/reason
# On failure: falls back to uncompressed POST (WebUtil.PostToService) with warning that destination should be updated
# Returns false with reason on all failure paths

==== UpdateAgent(destination, AgentData, ctx) ====

Full agent data update (region crossing). Timeout 200 seconds.

==== UpdateAgent(destination, AgentPosition) ====

Position-only update. Called frequently during avatar movement.

Deduplication via m_updateAgentQueue dictionary keyed by URI:
* First thread for a URI becomes the worker; subsequent threads update the map and return
* Worker loops, sending the most recent position until no new update arrives
* On send failure: blacklists the destination URI for 120 seconds via _failedSims ExpiringCache
* Blacklisted destinations return false immediately without attempting contact

Private UpdateAgent(destination, IAgentData, ctx, timeout) handles the actual PUT:
* Uses PutToServiceCompressed
* If OutboundVersion >= 0.3: returns immediately on success
* If OutboundVersion < 0.2: falls back to uncompressed PutToService on failure

==== QueryAccess() ====

public bool QueryAccess(GridRegion destination, UUID agentID, string agentHomeURI, bool viaTeleport, Vector3 position, List<UUID> featuresAvailable, EntityTransferContext ctx, out string reason)

URL: destination.ServerURI + "agent/" + agentID + "/" + destination.RegionID + "/"

Sends simulation service version negotiation fields:
* simulation_service_supported_min/max
* simulation_service_accepted_min/max
* my_version (legacy field, set to minimum for safety)
* features (List of UUID capabilities)
* context

Response handling:
* Reads _Result map for success, reason, negotiated_inbound_version, negotiated_outbound_version
* Falls back to legacy "version" field (SIMULATION/N.N format) if negotiated fields absent
* Sets ctx.InboundVersion and ctx.OutboundVersion from response
* If MethodNotAllowed error received: logs it and returns true (legacy simulator compatibility)
* Sets ctx.WearablesCount based on OutboundVersion:
** < 0.5: LEGACY_VERSION_MAX_WEARABLES
** < 0.6: LEGACY_VERSION_MAX_WEARABLES + 1
** >= 0.6: -1 (send all)
* Clears featuresAvailable and repopulates from response

Comment in source notes the _Result success/failure is the authoritative one, not the sibling result node -- legacy issue from 0.7.3.1 era labelled "nte4.8 crap".

==== ReleaseAgent() ====

Sends DELETE to a provided URI (not constructed from destination). Always returns true regardless of result.

==== CloseAgent() ====

URL: destination.ServerURI + "agent/" + id + "/" + destination.RegionID + "/?auth=" + auth_code

Sends DELETE. Always returns true regardless of result.

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=== Object Methods ===

==== CreateObject(destination, newPosition, sog, isLocalCall) ====

URL: destination.ServerURI + "object/" + sog.UUID + "/"

Packs scene object as XML2 via sog.ToXml2(), extra state via ExtraToXmlString() and GetStateSnapshot(). Sends uncompressed POST. Returns false if result is null or success is false.

==== CreateObject(destination, userID, itemID) ====

Not implemented. Always returns false with a TODO comment.

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=== Notes ===

* This connector talks to region simulators, not ROBUST. The destination URI comes from GridRegion.ServerURI per call.
* The compressed/uncompressed fallback in CreateAgent() exists for backward compatibility with older simulators. A warning is logged when the fallback is needed.
* UpdateAgent position deduplication means only the most recent position is ever sent -- intermediate positions are silently dropped. This is intentional.
* The 200-second timeout on full AgentData UpdateAgent is notably long -- comment "yes, 200 seconds" is in the source.
* ReleaseAgent and CloseAgent always return true -- callers cannot detect failure from return value.
* CreateObject by userID+itemID is explicitly unimplemented with a "TODO, not that urgent" comment.

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== See Also ==

* [[OpenSimulator Internals/Connector Architecture]]
* [[OpenSimulator Internals/Code Map/ROBUST/GatekeeperService]]
* [[OpenSimulator Internals/Code Map/Scene]]

OpenSimulator Internals/Connector Architecture/Simulation Connector - Revision history

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