lmxopcua/docs/drivers/Galaxy-Repository.md

Galaxy Repository — Tag Discovery for the Galaxy Driver

GalaxyRepositoryService reads the Galaxy object hierarchy and attribute metadata from the System Platform Galaxy Repository SQL Server database. It is the Galaxy driver's implementation of ITagDiscovery.DiscoverAsync — every driver has its own discovery source, and the Galaxy driver's is a direct SQL query against the Galaxy Repository (the ZB database). Other drivers use completely different mechanisms:

Driver	ITagDiscovery source
Galaxy	ZB SQL hierarchy + attribute queries (this doc)
AB CIP	@tags walker against the PLC controller
AB Legacy	Data-table scan via PCCC LogicalRead on the PLC
TwinCAT	Beckhoff SymbolLoaderFactory — uploads the full symbol tree from the ADS runtime
S7	Config-DB enumeration (no native symbol upload for S7comm)
Modbus	Config-DB enumeration (flat register map, user-authored)
FOCAS	CNC queries (cnc_rdaxisname, cnc_rdmacroinfo, …) + optional Config-DB overlays
OPC UA Client	Session.Browse against the remote server

GalaxyRepositoryService lives in src/ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Host/Backend/GalaxyRepository/ — Host-side, .NET Framework 4.8 x86, same process that owns the MXAccess COM objects. The Proxy forwards discovery over IPC the same way it forwards reads and writes.

Connection Configuration

GalaxyRepositoryConfiguration controls database access:

Property	Default	Description
ConnectionString	Server=localhost;Database=ZB;Integrated Security=true;	SQL Server connection using Windows Authentication
ChangeDetectionIntervalSeconds	30	Polling frequency for deploy change detection
CommandTimeoutSeconds	30	SQL command timeout for all queries
ExtendedAttributes	false	When true, loads primitive-level attributes in addition to dynamic attributes
Scope	Galaxy	Galaxy loads all deployed objects. LocalPlatform filters to the local platform's subtree only
PlatformName	null	Explicit platform hostname for LocalPlatform filtering. When null, uses Environment.MachineName

The connection uses Windows Authentication because the Galaxy Repository database is local to the System Platform node and secured through domain credentials.

SQL Queries

All queries are embedded as const string fields in GalaxyRepositoryService. No dynamic SQL is used. Project convention GR-006 requires const string SQL queries; any new query must be added as a named constant rather than built at runtime.

Hierarchy query

Returns deployed Galaxy objects with their parent relationships, browse names, and template derivation chains:

• Joins gobject to template_definition to filter by relevant category_id values (1, 3, 4, 10, 11, 13, 17, 24, 26)
• Uses contained_name as the browse name, falling back to tag_name when contained_name is null or empty
• Resolves the parent using contained_by_gobject_id when non-zero, otherwise falls back to area_gobject_id
• Marks objects with category_id = 13 as areas
• Filters to is_template = 0 (instances only, not templates)
• Filters to deployed_package_id <> 0 (deployed objects only)
• Returns a template_chain column built by a recursive CTE that walks gobject.derived_from_gobject_id from each instance through its immediate template and ancestor templates (depth guard < 10). Template names are ordered by depth and joined with | via STUFF(... FOR XML PATH('')). Example: TestMachine_001 returns $TestMachine|$gMachine|$gUserDefined|$UserDefined. The C# repository reader splits the column on |, trims, and populates GalaxyObjectInfo.TemplateChain, which is consumed by AlarmObjectFilter for template-based alarm filtering. See Alarm Tracking.
• Returns template_definition.category_id as a category_id column, populated into GalaxyObjectInfo.CategoryId. The runtime status probe manager filters this down to CategoryId == 1 ($WinPlatform) and CategoryId == 3 ($AppEngine) to decide which objects get a <Host>.ScanState probe advised. Also used during the hosted-variables walk to identify Platform/Engine ancestors.
• Returns gobject.hosted_by_gobject_id as a hosted_by_gobject_id column, populated into GalaxyObjectInfo.HostedByGobjectId. This is the runtime host of the object (e.g., which $AppEngine actually runs it), not the browse-containment parent (contained_by_gobject_id). The two are often different — an object can live in one Area in the browse tree but be hosted by an Engine on a different Platform for runtime execution. The driver walks this chain during BuildHostedVariablesMap to find the nearest $WinPlatform or $AppEngine ancestor so subtree quality invalidation on a Stopped host reaches exactly the variables that were actually executing there. Note: the Galaxy schema column is named hosted_by_gobject_id (not host_gobject_id as some documentation sources guess). See Galaxy driver — Per-Host Runtime Status Probes.

Attributes query (standard)

Returns user-defined dynamic attributes for deployed objects:

• Uses a recursive CTE (deployed_package_chain) to walk the package inheritance chain from deployed_package_id through derived_from_package_id, limited to 10 levels
• Joins dynamic_attribute on each package in the chain to collect inherited attributes
• Uses ROW_NUMBER() OVER (PARTITION BY gobject_id, attribute_name ORDER BY depth) to pick the most-derived definition when an attribute is overridden at multiple levels
• Builds full_tag_reference as tag_name.attribute_name with [] appended for arrays
• Extracts array_dimension from the binary mx_value column (bytes 13-16, little-endian int32)
• Detects historized attributes by checking for a HistoryExtension primitive instance
• Detects alarm attributes by checking for an AlarmExtension primitive instance
• Excludes internal attributes (names starting with _) and .Description suffixes
• Filters by mx_attribute_category to include only user-relevant categories

Attributes query (extended)

When ExtendedAttributes = true, a more comprehensive query runs that unions two sources:

1. Primitive attributes — Joins through primitive_instance and attribute_definition to include system-level attributes from primitive components. Each attribute carries its primitive_name so the address space can group them under their parent variable.
2. Dynamic attributes — The same CTE-based query as the standard path, with an empty primitive_name.

The full_tag_reference for primitive attributes follows the pattern tag_name.primitive_name.attribute_name (e.g., TestMachine_001.AlarmAttr.InAlarm).

Change detection query

A single-column query: SELECT time_of_last_deploy FROM galaxy. The galaxy table contains one row with the timestamp of the most recent deployment.

Why deployed_package_id Instead of checked_in_package_id

The Galaxy maintains two package references for each object:

• checked_in_package_id — the latest saved version, which may include undeployed configuration changes
• deployed_package_id — the version currently running on the target platform

The queries filter on deployed_package_id <> 0 because the OPC UA address space must mirror what is actually running in the Galaxy runtime. Using checked_in_package_id would expose attributes and objects that exist in the IDE but have not been deployed, causing mismatches between the OPC UA address space and the MXAccess runtime.

Platform Scope Filter

When Scope is set to LocalPlatform, the repository applies a post-query C# filter to restrict the address space to objects hosted by the local platform. This reduces memory footprint, MXAccess subscription count, and address space size on multi-node Galaxy deployments where each OPC UA server instance only needs to serve its own platform's objects.

How it works

1. Platform lookup — A separate const string SQL query (PlatformLookupSql) reads platform_gobject_id and node_name from the platform table for all deployed platforms. This runs once per hierarchy load.
2. Platform matching — The configured PlatformName (or Environment.MachineName when null) is matched case-insensitively against the node_name column. If no match is found, a warning is logged listing the available platforms and the address space is empty.
3. Host chain collection — The filter collects the matching platform's gobject_id, then iterates the hierarchy to find all $AppEngine (category 3) objects whose HostedByGobjectId equals the platform. This produces the full set of host gobject_ids under the local platform.
4. Object inclusion — All non-area objects whose HostedByGobjectId is in the host set are included, along with the hosts themselves.
5. Area retention — ParentGobjectId chains are walked upward from included objects to pull in ancestor areas, keeping the browse tree connected. Areas that contain no local descendants are excluded.
6. Attribute filtering — The set of included gobject_id values is cached after GetHierarchyAsync and reused by GetAttributesAsync to filter attributes to the same scope.

Design rationale

The filter is applied in C# rather than SQL because project convention GR-006 requires const string SQL queries with no dynamic SQL. The hierarchy query already returns HostedByGobjectId and CategoryId on every row, so all information needed for filtering is already in memory after the query runs. The only new SQL is the lightweight platform lookup query.

Configuration

"GalaxyRepository": {
    "Scope": "LocalPlatform",
    "PlatformName": null
}

• Set Scope to "LocalPlatform" to enable filtering. Default is "Galaxy" (load everything).
• Set PlatformName to an explicit hostname to target a specific platform, or leave null to use the local machine name.

Startup log

When LocalPlatform is active, the startup log shows the filtering result:

GalaxyRepository.Scope="LocalPlatform", PlatformName=MYNODE
GetHierarchyAsync returned 49 objects
GetPlatformsAsync returned 2 platform(s)
Scope filter targeting platform 'MYNODE' (gobject_id=1042)
Scope filter retained 25 of 49 objects for platform 'MYNODE'
GetAttributesAsync returned 4206 attributes (extended=true)
Scope filter retained 2100 of 4206 attributes

Change Detection Polling and IRediscoverable

ChangeDetectionService runs a background polling loop in the Host process that calls GetLastDeployTimeAsync at the configured interval. It compares the returned timestamp against the last known value:

• On the first poll (no previous state), the timestamp is recorded and OnGalaxyChanged fires unconditionally
• On subsequent polls, OnGalaxyChanged fires only when time_of_last_deploy differs from the cached value

When the event fires, the Host re-runs the hierarchy and attribute queries and pushes the result back to the Server via an IPC RediscoveryNeeded message. That surfaces on GalaxyProxyDriver as the IRediscoverable.OnRediscoveryNeeded event; the Server's DriverNodeManager consumes it and calls SyncAddressSpace to compute the diff against the live address space.

The polling approach is used because the Galaxy Repository database does not provide change notifications. The galaxy.time_of_last_deploy column updates only on completed deployments, so the polling interval controls how quickly the OPC UA address space reflects Galaxy changes.

TestConnection

TestConnectionAsync runs SELECT 1 against the configured database. This is used at Host startup to verify connectivity before attempting the full hierarchy query.

Key source files

• src/ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Host/Backend/GalaxyRepository/GalaxyRepositoryService.cs — SQL queries and data access
• src/ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Host/Backend/GalaxyRepository/PlatformScopeFilter.cs — Platform-based hierarchy and attribute filtering
• src/ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Host/Backend/GalaxyRepository/ChangeDetectionService.cs — Deploy timestamp polling loop
• src/ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Host/Configuration/GalaxyRepositoryConfiguration.cs — Connection, polling, and scope settings
• src/ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Host/Domain/PlatformInfo.cs — Platform-to-hostname DTO
• src/ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Shared/Contracts/DiscoveryResponse.cs — IPC DTO the Host uses to return hierarchy + attribute results across the pipe