Add manual load test file

spec/manual/load_test.cr

@@ -0,0 +1,54 @@
+# This file is to be executed as:
+#
+# % crystal ./spec/manual/load_test.cr
+#
+# It generated a number of producers and consumers. If the process hangs
+# it means that the connection pool is not working properly. Likely a race condition.
+#
+
+require "../dummy_driver"
+require "../../src/db"
+require "json"
+
+CONNECTION = "dummy://host?initial_pool_size=5&max_pool_size=5&max_idle_pool_size=5"
+
+alias TChannel = Channel(Int32)
+alias TDone = Channel(Bool)
+
+COUNT = 200
+
+def start_consumer(channel : TChannel, done : TDone)
+  spawn do
+    indeces = Set(Int32).new
+    loop do
+      indeces << channel.receive
+      puts "Received size=#{indeces.size}"
+      break if indeces.size == COUNT
+    end
+    done.send true
+  end
+end
+
+def start_producers(channel : TChannel)
+  db = DB.open CONNECTION do |db|
+    sql = "1,title,description,2023 " * 100_000
+
+    COUNT.times do |index|
+      spawn(name: "prod #{index}") do
+        puts "Sending #{index}"
+        _films = db.query_all(sql, as: {Int32, String, String, Int32})
+      rescue ex
+        puts "Error: #{ex.message}"
+      ensure
+        channel.send index
+      end
+    end
+  end
+end
+
+channel = TChannel.new
+done = TDone.new
+start_consumer(channel, done)
+start_producers(channel)
+
+done.receive