FIX: Bump rails_multisite and update usage (#42684)

`with_connection`, `with_hostname` and `establish_connection` no longer
silently fallback to the default db. When we want that fallback
behavior, we have to specifically opt-in.

For example:
- Most hostname-based lookups in Discourse should fallback to the
default site, so that we match the existing behavior for any sites which
may have misconfigured hostnames

- Loops like CachedCounting, keep_readonly_mode and sidekiq-pausable
should defensively skip attempts to connect to sites which are now
missing, so that they don't get blocked by an exception for one missing
site

Depends on https://github.com/discourse/rails_multisite/pull/40

Gemfile.lock

@@ -535,9 +535,9 @@ GEM
       activerecord (>= 6.1, < 9.0)
       concurrent-ruby
       railties (>= 6.1, < 9.0)
-    rails_multisite (7.0.0)
-      activerecord (>= 7.1)
-      railties (>= 7.1)
+    rails_multisite (9.0.0)
+      activerecord (>= 7.2)
+      railties (>= 7.2)
     railties (8.0.5.1)
       actionpack (= 8.0.5.1)
       activesupport (= 8.0.5.1)
@@ -1218,7 +1218,7 @@ CHECKSUMS
   rails-dom-testing (2.3.0) sha256=8acc7953a7b911ca44588bf08737bc16719f431a1cc3091a292bca7317925c1d
   rails-html-sanitizer (1.7.1) sha256=e797a7c9b01e567307e317c576b49ab4168017e63eea4dba9ce3cb587e2f22c2
   rails_failover (2.3.0) sha256=eed6ea0674fd6f9f6b070ad297ad2ead121ecf9202920f6068b6a4f29d9491c9
-  rails_multisite (7.0.0) sha256=7aacf364ed86d2bee73fb679cbfe6c343ce89067b9746b3d5857fffc57f036f2
+  rails_multisite (9.0.0) sha256=2bc88f0405cb88d1055712095a11c4eb8ce1d4a36599d1226c6779946be495e6
   railties (8.0.5.1) sha256=da1958e1d9dab04691a2f8721b3ff7fab323715d37f103c19972dedfd644d5c7
   rainbow (3.1.1) sha256=039491aa3a89f42efa1d6dec2fc4e62ede96eb6acd95e52f1ad581182b79bc6a
   raindrops (0.20.1) sha256=aa0eb9ff6834f2d9e232ba688bd49cb30be893bc5a3452e74722c94c1fab4730

app/controllers/highlight_js_controller.rb

@@ -13,7 +13,10 @@ class HighlightJsController < ApplicationController
   def show
     no_cookies
 
-    RailsMultisite::ConnectionManagement.with_hostname(params[:hostname]) do
+    RailsMultisite::ConnectionManagement.with_hostname(
+      params[:hostname],
+      raise_on_missing: false,
+    ) do
       current_version = HighlightJs.version(SiteSetting.highlighted_languages)
 
       return redirect_to path(HighlightJs.path) if current_version != params[:version]

app/controllers/svg_sprite_controller.rb

@@ -18,7 +18,10 @@ class SvgSpriteController < ApplicationController
   def show
     no_cookies
 
-    RailsMultisite::ConnectionManagement.with_hostname(params[:hostname]) do
+    RailsMultisite::ConnectionManagement.with_hostname(
+      params[:hostname],
+      raise_on_missing: false,
+    ) do
       theme_id = params[:theme_id].to_i if params[:theme_id].present?
 
       if SvgSprite.version(theme_id) != params[:version]
@@ -70,7 +73,10 @@ class SvgSpriteController < ApplicationController
   def svg_icon
     no_cookies
 
-    RailsMultisite::ConnectionManagement.with_hostname(params[:hostname]) do
+    RailsMultisite::ConnectionManagement.with_hostname(
+      params[:hostname],
+      raise_on_missing: false,
+    ) do
       params.permit(:color)
       name = params.require(:name)
       icon = SvgSprite.search(name)

app/controllers/user_avatars_controller.rb

@@ -87,9 +87,10 @@ class UserAvatarsController < ApplicationController
     is_asset_path
 
     # we need multisite support to keep a single origin pull for CDNs
-    RailsMultisite::ConnectionManagement.with_hostname(params[:hostname]) do
-      hijack { show_in_site(params[:hostname]) }
-    end
+    RailsMultisite::ConnectionManagement.with_hostname(
+      params[:hostname],
+      raise_on_missing: false,
+    ) { hijack { show_in_site(params[:hostname]) } }
   end
 
   protected

app/models/concerns/cached_counting.rb

@@ -128,6 +128,10 @@ module CachedCounting
             # could be a race condition in test
             if val > 0
               klass_name, db, date, local_key = key.split(",", 4)
+
+              # the site may have been deleted since the count was recorded
+              next if !RailsMultisite::ConnectionManagement.has_db?(db)
+
               date = Date.strptime(date, "%Y%m%d")
               klass = Module.const_get(klass_name)
 

config/initializers/004-message_bus.rb

@@ -25,7 +25,7 @@ def setup_message_bus_env(env)
   end
 
   host = RailsMultisite::ConnectionManagement.host(env)
-  RailsMultisite::ConnectionManagement.with_hostname(host) do
+  RailsMultisite::ConnectionManagement.with_hostname(host, raise_on_missing: false) do
     cors_origin = Discourse.base_url_no_prefix
 
     if GlobalSetting.enable_cors && SiteSetting.cors_origins.present?

lib/discourse.rb

@@ -840,6 +840,11 @@ module Discourse
 
             @mutex.synchronize do
               @dbs.each do |db|
+                if !RailsMultisite::ConnectionManagement.has_db?(db)
+                  @dbs.delete(db)
+                  next
+                end
+
                 RailsMultisite::ConnectionManagement.with_connection(db) do
                   @dbs.delete(db) if !Discourse.redis.expire(key, ttl)
                 end

lib/sidekiq/pausable.rb

@@ -77,6 +77,11 @@ class SidekiqPauser
 
             @mutex.synchronize do
               @dbs.each do |db|
+                if !RailsMultisite::ConnectionManagement.has_db?(db)
+                  @dbs.delete(db)
+                  next
+                end
+
                 RailsMultisite::ConnectionManagement.with_connection(db) do
                   if !Discourse.redis.expire(PAUSED_KEY, TTL)
                     # if it was unpaused in another process we got to remove the
@@ -135,8 +140,9 @@ class Sidekiq::Pausable
   private
 
   def sidekiq_paused?(msg)
-    if site_id = msg["args"]&.first&.dig("current_site_id")
-      RailsMultisite::ConnectionManagement.with_connection(site_id) { Sidekiq.paused? }
-    end
+    site_id = msg["args"]&.first&.dig("current_site_id")
+    return false if !site_id || !RailsMultisite::ConnectionManagement.has_db?(site_id)
+
+    RailsMultisite::ConnectionManagement.with_connection(site_id) { Sidekiq.paused? }
   end
 end

spec/lib/concern/cached_counting_spec.rb

@@ -48,6 +48,20 @@ RSpec.describe CachedCounting do
 
         expect(TestCachedCounting.data).to eq({ "a,a" => 2, "b" => 1 })
       end
+
+      it "drops counts for a site that no longer exists" do
+        Discourse.redis.without_namespace.hincrby(
+          CachedCounting::COUNTER_REDIS_HASH,
+          "TestCachedCounting,gone-site,#{Time.zone.now.strftime("%Y%m%d")},a",
+          1,
+        )
+        CachedCounting.queue("b", TestCachedCounting)
+
+        CachedCounting.flush_in_memory
+        CachedCounting.flush_to_db
+
+        expect(TestCachedCounting.data).to eq({ "b" => 1 })
+      end
     end
   end
 

spec/lib/scheduler/defer_spec.rb

@@ -120,6 +120,13 @@ RSpec.describe Scheduler::Defer do
     let!(:ivar) { Concurrent::IVar.new }
     let!(:responses) { Thread::Queue.new }
 
+    before do
+      # "site1"/"site2" here are fairness-queue tags, not real dbs
+      allow(RailsMultisite::ConnectionManagement).to receive(:with_connection) do |_db, &blk|
+        blk.call
+      end
+    end
+
     def later(db, current_user, request)
       @defer.later(nil, db, current_user: current_user) do
         ivar.value

spec/multisite/pausable_multisite_spec.rb

@@ -65,5 +65,14 @@ RSpec.describe Sidekiq::Pausable, type: :multisite do
         expect(called2).to eq(true)
       end
     end
+
+    it "runs a job for a site this process does not know about" do
+      Sidekiq.pause!
+
+      called = false
+      call_middleware("unknown-site") { called = true }
+
+      expect(called).to eq(true)
+    end
   end
 end

spec/requests/asset_hostname_multisite_spec.rb

@@ -0,0 +1,32 @@
+# frozen_string_literal: true
+
+# The asset routes below take the site's hostname as a path segment so a CDN can
+# pull every site through a single origin. The segment is unvalidated, so an
+# unknown one has to fall back to the default site rather than error.
+RSpec.describe "Asset routes with a hostname segment", type: %i[multisite request] do
+  it "serves svg sprites for an unknown hostname" do
+    get "/svg-sprite/unknown.example.com/svg--#{SecureRandom.hex(20)}.js"
+
+    expect(response.status).to eq(302)
+  end
+
+  it "serves svg icons for an unknown hostname" do
+    get "/svg-sprite/unknown.example.com/icon/heart.svg"
+
+    expect(response.status).to eq(200)
+  end
+
+  it "serves highlight.js for an unknown hostname" do
+    get "/highlight-js/unknown.example.com/stale.js"
+
+    expect(response.status).to eq(302)
+  end
+
+  it "serves avatars for an unknown hostname" do
+    user = Fabricate(:user)
+
+    get "/user_avatar/unknown.example.com/#{user.username}/45/1.png"
+
+    expect(response.status).to eq(200)
+  end
+end