feat: print warning if db pool is less than rpc pool

CHANGELOG.md

@@ -2,7 +2,9 @@
 
 ## master
 
-- Add support for broadcast options (e.g., `exclude_socket`). ([@palkan][])
+- Print warning if the database pool size is less than RPC pool size. ([@palkan][])
+
+- Add support for broadcast options (e.g., `exclude_socket`) and `broadcast ..., to_others: true`. ([@palkan][])
 
 - Add `batch_broadcasts` option to automatically batch broadcasts for code wrapped in Rails executor. ([@palkan][])
 

lib/anycable/rails/config.rb

@@ -17,6 +17,7 @@
   embedded: false,
   http_rpc_mount_path: nil,
   batch_broadcasts: false,
-  socket_id_header: "X-Socket-ID"
+  socket_id_header: "X-Socket-ID",
+  disable_rpc_pool_size_warning: false
 )
 AnyCable::Config.ignore_options :access_logs_disabled, :persistent_session_enabled

lib/anycable/rails/railtie.rb

@@ -108,6 +108,25 @@ class Railtie < ::Rails::Railtie # :nodoc:
         end
       end
 
+      initializer "anycable.verify_pool_sizes" do
+        next if AnyCable.config.disable_rpc_pool_size_warning?
+        # Skip if non-gRPC server is used
+        next unless AnyCable.config.respond_to?(:rpc_pool_size)
+
+        # Log current db vs. gRPC pool sizes
+        AnyCable.configure_server do
+          db_pool_size = ActiveRecord::Base.connection_pool.size
+          rpc_pool_size = AnyCable.config.rpc_pool_size
+
+          if rpc_pool_size > db_pool_size
+            ::Kernel.warn(
+              "\n⛔️ WARNING: AnyCable RPC pool size (#{rpc_pool_size}) is greater than DB pool size (#{db_pool_size})\n" \
+              "Please, consider adjusting the database pool size to avoid connection wait times and increase throughput of your RPC server\n\n"
+            )
+          end
+        end
+      end
+
       # Since Rails 6.1
       if respond_to?(:server)
         server do

spec/integrations/rails_integration_spec.rb

@@ -60,4 +60,13 @@ def app
       expect(context[:payload]).to be_a(Hash)
     end
   end
+
+  context "database pool check" do
+    before { allow(Kernel).to receive(:warn) }
+
+    specify do
+      AnyCable.server_callbacks.last.call
+      expect(Kernel).to have_received(:warn).with(/is greater than DB pool size/)
+    end
+  end
 end