chore: enhance log lack of connections

lib/realtime/database.ex

@@ -87,9 +87,6 @@ defmodule Realtime.Database do
 
   @available_connection_factor 0.95
 
-  defguardp can_connect?(available_connections, required_pool)
-            when required_pool * @available_connection_factor < available_connections
-
   @doc """
   Checks if the Tenant CDC extension information is properly configured and that we're able to query against the tenant database.
   """
@@ -110,12 +107,19 @@ defmodule Realtime.Database do
           "select (current_setting('max_connections')::int - count(*))::int from pg_stat_activity where application_name != 'realtime_connect'"
 
         case Postgrex.query(conn, query, []) do
-          {:ok, %{rows: [[available_connections]]}}
-          when can_connect?(available_connections, required_pool) ->
-            {:ok, conn}
-
-          {:ok, _} ->
-            {:error, :tenant_db_too_many_connections}
+          {:ok, %{rows: [[available_connections]]}} ->
+            requirement = ceil(required_pool * @available_connection_factor)
+
+            if requirement < available_connections do
+              {:ok, conn}
+            else
+              log_error(
+                "DatabaseLackOfConnections",
+                "Only #{available_connections} available connections. At least #{requirement} connections are required."
+              )
+
+              {:error, :tenant_db_too_many_connections}
+            end
 
           {:error, e} ->
             Process.exit(conn, :kill)

mix.exs

@@ -4,7 +4,7 @@ defmodule Realtime.MixProject do
   def project do
     [
       app: :realtime,
-      version: "2.55.1",
+      version: "2.55.2",
       elixir: "~> 1.17.3",
       elixirc_paths: elixirc_paths(Mix.env()),
       start_permanent: Mix.env() == :prod,

test/realtime/database_test.exs

@@ -48,11 +48,13 @@ defmodule Realtime.DatabaseTest do
 
     # Connection limit for docker tenant db is 100
     @tag db_pool: 50,
-         subs_pool_size: 50,
-         subcriber_pool_size: 50
+         subs_pool_size: 21,
+         subcriber_pool_size: 33
     test "restricts connection if tenant database cannot receive more connections based on tenant pool",
          %{tenant: tenant} do
-      assert {:error, :tenant_db_too_many_connections} = Database.check_tenant_connection(tenant)
+      assert capture_log(fn ->
+               assert {:error, :tenant_db_too_many_connections} = Database.check_tenant_connection(tenant)
+             end) =~ ~r/Only \d+ available connections\. At least 126 connections are required/
     end
   end