[Audit] Marten ↔ Polecat dedup — multi-tenancy slice

[jeremydmiller]

Status: in-flight
Third slice of the dedup audit deliverable under pillar #214.
Prior slices: #218 (database-manipulation), #219 (events / projections).
Scope: multi-tenancy strategies cluster — anything in Marten or Polecat that fits Rule 1 (non-database) targeting JasperFx.MultiTenancy, or Rule 2 (database) targeting Weasel.Core.MultiTenancy.

Headline

This slice is mostly already done, much like the events/projections slice. The heavy consolidation of the multi-tenancy substrate — IHasTenantId, TenantId, TenantIdStyle, UnknownTenantIdException, dynamic / static tenant sources — has already happened in JasperFx.MultiTenancy. The strategy implementations (MasterTableTenancy, SeparateDatabaseTenancy, etc.) are database-coupled and rightfully stay product-side. The shared options shell (MasterTableTenancyOptions<T>) and the assignment strategies (HashTenantAssignment, SmallestTenantAssignment, ExplicitTenantAssignment, ITenantDatabasePool) already live in Weasel.Core.MultiTenancy.

The audit found exactly two Polecat-side rows that warrant migration, plus a low-priority ergonomic addition to JasperFx.

Active migrations (sub-issues filed)

• Row 1 — Polecat ITenanted should extend IHasTenantId
  Marten's Marten.Metadata.ITenanted : IHasTenantId already extends the canonical JasperFx marker (a one-line implementation). Polecat's Polecat.Metadata.ITenanted re-declares its own string TenantId { get; set; } property without extending IHasTenantId, so Polecat-side framework code can't accept arbitrary IHasTenantId values. Migration: Polecat's ITenanted extends IHasTenantId (drop the local TenantId property since the base contributes it). Rule 1.
  → polecat#TBD (filed below)

• Row 2 — Polecat UnknownTenantException → JasperFx.MultiTenancy.UnknownTenantIdException
  Polecat has Polecat.Exceptions.UnknownTenantException with a TenantId property and a Polecat-specific message. JasperFx has JasperFx.MultiTenancy.UnknownTenantIdException with a generic message and no TenantId property. Marten already consumes the JasperFx one directly (see Marten.Storage.ITenancy.GetTenant XML doc). Migration: Polecat drops the local exception; consumes the JasperFx version. Rule 4 (exception duplicated across products) + Rule 1.
  → polecat#TBD (filed below)

Optional JasperFx-side ergonomic addition (low priority)

• Add TenantId property to JasperFx.MultiTenancy.UnknownTenantIdException
  Polecat's local exception carries a TenantId getter; the canonical JasperFx one does not. The id is in the message string but isn't programmatically accessible. Adding it is additive and unblocks Polecat consumers that want to catch + inspect. Worth doing alongside the Polecat migration so the Polecat side doesn't regress on diagnostics.
  → can be folded into Row 2's Polecat PR via a small JasperFx-side companion, or filed as a standalone JasperFx issue if preferred.

Already in JasperFx.MultiTenancy (no action needed)

The agent confirmed both products correctly consume these:

• IHasTenantId — marker interface with string? TenantId { get; set; }
• TenantId — value type
• TenantIdStyle enum (CaseSensitive, ForceUpperCase, ForceLowerCase) + MaybeCorrectTenantId extension
• UnknownTenantIdException (Marten consumes; Polecat doesn't yet — Row 2)
• IDynamicTenantSource — dynamic tenant lookup
• ITenantedSource — abstract tenanted source

Already in Weasel.Core.MultiTenancy (no action needed)

• MasterTableTenancyOptions<T> (Marten's MasterTableTenancyOptions is a Postgres NpgsqlDataSource shim over it)
• ExplicitTenantAssignment, HashTenantAssignment, SmallestTenantAssignment
• IDatabaseSizingStrategy, ITenantAssignmentStrategy, ITenantDatabasePool
• MasterTableMultiTenancyExtensions
• PooledDatabase

Polecat doesn't currently use the master-table tenancy pattern, so there's no Polecat-side gap here.

Correctly product-specific (no migration)

Audited and confirmed these stay where they are — they encode product-specific storage primitives or use-cases without cross-product parallels:

• Marten.Storage.ITenancy vs Polecat.Storage.ITenancy — different shapes. Marten's extends IDatabaseSource, IDisposable, IDatabaseUser and returns Marten.Storage.Tenant + IMartenDatabase; Polecat's exposes DatabaseCardinality, ConnectionFactory, PolecatDatabase. Both correctly DB-specific.
• Marten tenancy strategies — DefaultTenancy, MasterTableTenancy, ShardedTenancy, SingleServerMultiTenancy, StaticMultiTenancy. All Postgres-specific.
• Polecat tenancy strategies — DefaultTenancy, SeparateDatabaseTenancy. SQL-Server-specific.
• Marten.Storage.TenancyStyle — Single, Conjoined. Marten-only; Polecat doesn't model conjoined tenancy as an enum.
• Marten.Schema.Indexing.Unique.TenancyScope — Global, PerTenant. Index-tenancy scope; no Polecat equivalent.
• Polecat.Internal.DatabaseCardinality — different concept from Marten's TenancyStyle; describes connection routing, not data-scoping.
• Polecat.Linq.SqlGeneration.TenantInFilter — LINQ-tenancy filter. SQL-Server-specific.
• Marten.Metadata.TenancyPolicy — Marten-only document-mapping policy hook.

Slice exit criteria

• Both active sub-issues closed.
• No remaining duplicated multi-tenancy abstractions between Marten and Polecat (excluding the product-specific list above).
• No regressions in either product's tenancy tests.

Method

Same as the prior slices: focused structural compare across marten/src/Marten/Storage/, marten/src/Marten/Metadata/, polecat/src/Polecat/Storage/, polecat/src/Polecat/Metadata/, polecat/src/Polecat/Exceptions/, jasperfx/src/JasperFx/MultiTenancy/, and weasel/src/Weasel.Core/MultiTenancy/. Per-row decisions follow the propose-and-ratify pattern: propose target home + rule classification; ratify in conversation; reflect above.

Next slice

The pillar #214 inventory has four remaining clusters that could be candidate next slices:

• Document store metadata / descriptors — most of this already moved during the CritterWatch descriptor work, but a sweep would confirm nothing slipped.
• Schema migration & DDL diffing — Weasel charter territory; lower-priority because divergence is unlikely (both products use Weasel for DDL).
• Async daemon abstractions — partially confirmed in the events slice; a focused re-audit could close any leftover gaps.
• Helper utilities / JasperFx.Core overflow — any utility code that's grown product-side and is general-purpose.

Recommendation: document store metadata / descriptors as the next slice — the CritterWatch work was extensive and a verification pass closes the loop.

[jeremydmiller]

Status update — 2026-05-12

Caught a discrepancy doing the dedup-push planning today: both Row 1 and Row 2 were silently completed already but never marked here, and their "polecat#TBD (filed below)" placeholders never got real issue numbers because the work was done before the sub-issues got filed.

• Row 1 — Polecat.Metadata.ITenanted extends IHasTenantId → ✅ done. Polecat-side file src/Polecat/Metadata/ITenanted.cs declares public interface ITenanted : IHasTenantId and the local TenantId property is gone.

• Row 2 — Polecat drops UnknownTenantException, consumes JasperFx.MultiTenancy.UnknownTenantIdException → ✅ done. Polecat.Exceptions.UnknownTenantException no longer exists in the tree; throw sites in src/Polecat/Storage/ITenancy.cs:74,82 and the test at Polecat.Tests/MultiTenancy/separate_database_tenancy_tests.cs:187 use the JasperFx canonical UnknownTenantIdException.

What's actually left

• JasperFx-side ergonomic addition — add TenantId property to JasperFx.MultiTenancy.UnknownTenantIdException so Polecat consumers can catch (UnknownTenantIdException ex) { var id = ex.TenantId; ... } without parsing the message string. Polecat's old local exception had this getter; the canonical doesn't yet. Doing this today and cutting JasperFx 2.0.0-alpha.7.

[jeremydmiller]

Status update — JasperFx companion landed

PR #240 merged + JasperFx 2.0.0-alpha.7 is live on NuGet. UnknownTenantIdException now exposes TenantId as a property; Polecat consumers picking up alpha.7 (via polecat#61, CI all green) close the diagnostics regression that this slice surfaced.

With Rows 1 + 2 already complete (per the earlier status correction) and the companion landed, this slice is done end-to-end modulo the Polecat pin-bump merging.

[jeremydmiller]

Closing as complete:

Row	Status
1 — Polecat ITenanted extends IHasTenantId	✅ already in master before the audit was formalized (status correction posted earlier)
2 — Polecat drops UnknownTenantException, consumes JasperFx.MultiTenancy.UnknownTenantIdException	✅ already in master before the audit was formalized
Optional companion — TenantId property on UnknownTenantIdException	✅ #240, shipped in JasperFx 2.0.0-alpha.7