FEATURE: basic implementation of stats socket

lib/stats_socket.rb

@@ -0,0 +1,63 @@
+require 'socket'
+
+class StatsSocket
+
+  def initialize(socket_path)
+    @socket_path = socket_path
+    @server = nil
+  end
+
+  def start
+    @server = UNIXServer.new(@socket_path)
+    @accept_thread = new_accept_thread
+  end
+
+  def stop
+    @server.close if @server
+    @server = nil
+  end
+
+  protected
+
+  def new_accept_thread
+    server = @server
+    Thread.new do
+      done = false
+      while !done
+        done = !accept_connection(server)
+      end
+    end
+  end
+
+  def accept_connection(server)
+    socket = nil
+    begin
+      socket = server.accept
+    rescue IOError
+      # socket was shut down or something catastrophic like that happened
+      return false
+    end
+
+    line = socket.readline
+    socket.write get_response(line.strip)
+    socket.close
+    true
+  rescue IOError
+    # nothing to do here, case its normal on shutdown
+  rescue => e
+    Rails.logger.warn("Failed to handle connection in stats socket #{e}")
+  end
+
+  def get_response(command)
+    result =
+      case command
+      when "gc_stat"
+        GC.stat.to_json
+      else
+        "[\"UNKNOWN COMMAND\"]"
+      end
+
+    result << "\n"
+  end
+
+end

spec/components/stats_socket_spec.rb

@@ -0,0 +1,37 @@
+require 'rails_helper'
+require_dependency 'stats_socket'
+
+describe StatsSocket do
+  let :socket_path do
+    "#{Dir.tmpdir}/#{SecureRandom.hex}"
+  end
+
+  let :stats_socket do
+    StatsSocket.new(socket_path)
+  end
+
+  before do
+    stats_socket.start
+  end
+
+  after do
+    stats_socket.stop
+  end
+
+  it "can respond to various stats commands" do
+    line = nil
+
+    # ensure this works more than once :)
+    2.times do
+      socket = UNIXSocket.new(socket_path)
+      socket.send "gc_stat\n", 0
+      line = socket.readline
+      socket.close
+    end
+
+    parsed = JSON.parse(line)
+
+    expect(parsed.keys.sort).to eq(GC.stat.keys.map(&:to_s).sort)
+  end
+
+end