Implement UntenantedConnectionPool#size (#224)

so the mock object can be inspected for that config param. This allows,
e.g. Solid Queue to boot up on a tenanted database.

Author: flavorjones

CHANGELOG.md

@@ -2,7 +2,7 @@
 
 ## next / unreleased
 
-### Changed
+### Breaking change: Rake tasks
 
 Some rake task changes to rename tasks for the database name (like Rails does it):
 
@@ -24,6 +24,11 @@ Some additional changes:
 - `ActiveRecord::Tenanted.base_configs` is a new utility method that returns all the tenanted base configs for the current environment.
 
 
+### Added
+
+- `UntenantedConnectionPool#size` returns the database configuration's `max_connections` value, so that code (like Solid Queue) can inspect config params without a tenant context.
+
+
 ## v0.5.0 / 2025-10-12
 
 ### Fixed

GUIDE.md

@@ -10,7 +10,7 @@
 
 ## Contents
 
-<!-- regenerate TOC with `rake format:toc` -->
+<!-- regenerate TOC with `rake toc` -->
 
 <!-- toc -->
 
@@ -19,6 +19,7 @@
   * [1.2 High-level implementation](#12-high-level-implementation)
   * [1.3 Concepts](#13-concepts)
   * [1.4 Prior Art](#14-prior-art)
+  * [1.5 Shared state (WIP)](#15-shared-state-wip)
 - [2. Application Configuration](#2-application-configuration)
   * [2.1 The Default Configuration](#21-the-default-configuration)
   * [2.2 Configuring the Database](#22-configuring-the-database)
@@ -127,6 +128,17 @@ In December 2020, [Rails 6.1 was released](https://guides.rubyonrails.org/6_1_re
 In early 2025, Julik Tarkhanov published a [tenanting implementation named "Shardine"](https://blog.julik.nl/2025/04/a-can-of-shardines) that uses the Rails sharding API. However, it also provided very limited integration with the rest of the Rails framework.
 
 
+### 1.5 Shared state (WIP)
+
+- when we talk about "integration with the rest of rails" we're talking about Rails' assumptions about shared state
+- some of these assumptions are now busted
+  - database ids are no longer unique
+  - global ids are no longer global
+  - cache is no longer global
+  - cable channels are no longer global
+  - jobs are no longer global
+
+
 ## 2. Application Configuration
 
 This gem offers an "omakase" configuration that specifies:
@@ -384,19 +396,10 @@ TODO:
 
 Documentation outline:
 
-  - configuring either tenant-by-subdomain or a tenant-by-root-path-element
-  - fragment cache disambiguation
-  - global id disambiguation
-  - invalid characters in a tenant name
+  - invalid characters in a tenant name (which is database-dependent)
     - and how the application may want to do additional validation (e.g. ICANN subdomain restrictions)
   - `#tenant` is a readonly attribute on all tenanted model instances
   - `.current_tenant` returns the execution context for the model connection class
-- talk a bit about busted assumptions about shared state
-  - database ids are no longer unique
-  - global ids are no longer global
-  - cache is no longer global
-  - cable channels are no longer global
-  - jobs are no longer global
 - and what we do in this gem to help manage that "current tenant" state
 - logging
   - SQL query logs

lib/active_record/tenanted/untenanted_connection_pool.rb

@@ -28,6 +28,10 @@ def schema_cache
         ActiveRecord::ConnectionAdapters::BoundSchemaReflection.new(schema_reflection, self)
       end
 
+      def size
+        db_config.max_connections
+      end
+
       def lease_connection(...)
         raise Tenanted::NoTenantError, "Cannot connect to a tenanted database while untenanted (#{@model})."
       end

test/unit/untenanted_connection_pool_test.rb

@@ -19,5 +19,10 @@
         assert_equal("Cannot connect to a tenanted database while untenanted (User).", e.message)
       end
     end
+
+    test "size returns max_connections from db_config" do
+      def config.max_connections; 42; end
+      assert_equal 42, subject.size
+    end
   end
 end