diff --git a/shard.lock b/shard.lock
index 00cf4ce..f6251c4 100644
--- a/shard.lock
+++ b/shard.lock
@@ -2,7 +2,7 @@ version: 2.0
 shards:
   ameba:
     git: https://github.com/crystal-ameba/ameba.git
-    version: 1.6.1
+    version: 1.6.4
 
   amq-protocol:
     git: https://github.com/cloudamqp/amq-protocol.cr.git
@@ -10,5 +10,5 @@ shards:
 
   amqp-client:
     git: https://github.com/cloudamqp/amqp-client.cr.git
-    version: 1.2.5
+    version: 1.3.0
 
diff --git a/spec/spec_helper.cr b/spec/spec_helper.cr
index b0036bf..2c3106b 100644
--- a/spec/spec_helper.cr
+++ b/spec/spec_helper.cr
@@ -31,6 +31,7 @@ end
 def with_http_server(idle_connection_timeout = 5, &)
   with_server do |server, amqp_url|
     http_server = AMQProxy::HTTPServer.new(server, "127.0.0.1", 15673)
+    spawn { http_server.listen }
     begin
       yield http_server, server, amqp_url
     ensure
@@ -45,6 +46,7 @@ def verify_running_amqp!
   port = UPSTREAM_URL.port || 5762
   port = 5671 if tls && UPSTREAM_URL.port.nil?
   TCPSocket.new(host, port, connect_timeout: 3.seconds).close
+  puts "AMQP running"
 rescue Socket::ConnectError
   STDERR.puts "[ERROR] Specs require a running rabbitmq server on #{host}:#{port}"
   exit 1
diff --git a/src/amqproxy.cr b/src/amqproxy.cr
index e3b019a..9eb827a 100644
--- a/src/amqproxy.cr
+++ b/src/amqproxy.cr
@@ -1,2 +1,15 @@
 require "./amqproxy/cli"
+{% begin %}
+  {%
+    flags = [] of String
+    flags << "-Dpreview_mt" if flag?(:preview_mt)
+    flags << "-Dmt" if flag?(:mt)
+    flags << "-Dexecution_context" if flag?(:execution_context)
+    flags << "-Dtracing" if flag?(:tracing)
+    flags << "--release" if flag?(:release)
+    flags << "--static" if flag?(:static)
+    flags << "--debug" if flag?(:debug)
+  %}
+  puts "Built with #{Crystal::VERSION} #{Crystal::BUILD_COMMIT} {{flags.join(" ").id}}"
+{% end %}
 AMQProxy::CLI.new.run(ARGV)
diff --git a/src/amqproxy/cli.cr b/src/amqproxy/cli.cr
index 24e5ce2..7d9cced 100644
--- a/src/amqproxy/cli.cr
+++ b/src/amqproxy/cli.cr
@@ -119,9 +119,9 @@ class AMQProxy::CLI
 
     server = @server = AMQProxy::Server.new(u.hostname || "", port, tls, @idle_connection_timeout)
 
-    HTTPServer.new(server, @listen_address, @http_port.to_i)
+    http_server = HTTPServer.new(server, @listen_address, @http_port.to_i)
+    spawn http_server.listen, name: "HTTP Server"
     server.listen(@listen_address, @listen_port.to_i)
-
     shutdown
 
     # wait until all client connections are closed
@@ -133,11 +133,12 @@ class AMQProxy::CLI
 
   @first_shutdown = true
 
-  def initiate_shutdown(_s : Signal)
+  def initiate_shutdown(signal : Signal)
     unless server = @server
       exit 0
     end
     if @first_shutdown
+      Log.info { "Shutting down due to signal #{signal}" }
       @first_shutdown = false
       server.stop_accepting_clients
     else
diff --git a/src/amqproxy/client.cr b/src/amqproxy/client.cr
index ffdc8a6..73a955d 100644
--- a/src/amqproxy/client.cr
+++ b/src/amqproxy/client.cr
@@ -40,9 +40,13 @@ module AMQProxy
       end
     end
 
+    private def with_channel_map(&)
+      yield @channel_map
+    end
+
     private def finish_publish(channel)
       buffer = @publish_buffers[channel]
-      if upstream_channel = @channel_map[channel]
+      if upstream_channel = with_channel_map &.[channel]
         upstream_channel.write(buffer.publish)
         upstream_channel.write(buffer.header)
         buffer.bodies.each do |body|
@@ -61,6 +65,7 @@ module AMQProxy
       socket.read_timeout = (@heartbeat / 2).ceil.seconds if @heartbeat > 0
       loop do
         frame = AMQ::Protocol::Frame.from_io(socket, IO::ByteFormat::NetworkEndian)
+        Log.trace { "Received frame: #{frame}" }
         @last_heartbeat = Time.monotonic
         case frame
         when AMQ::Protocol::Frame::Heartbeat # noop
@@ -70,13 +75,15 @@ module AMQProxy
           write AMQ::Protocol::Frame::Connection::CloseOk.new
           return
         when AMQ::Protocol::Frame::Channel::Open
-          raise "Channel already opened" if @channel_map.has_key? frame.channel
-          upstream_channel = channel_pool.get(DownstreamChannel.new(self, frame.channel))
-          @channel_map[frame.channel] = upstream_channel
+          with_channel_map do |channel_map|
+            raise "Channel already opened" if channel_map.has_key? frame.channel
+            upstream_channel = channel_pool.get(DownstreamChannel.new(self, frame.channel))
+            channel_map[frame.channel] = upstream_channel
+          end
           write AMQ::Protocol::Frame::Channel::OpenOk.new(frame.channel)
         when AMQ::Protocol::Frame::Channel::CloseOk
           # Server closed channel, CloseOk reply to server is already sent
-          @channel_map.delete(frame.channel)
+          with_channel_map &.delete(frame.channel)
         when AMQ::Protocol::Frame::Basic::Publish
           @publish_buffers[frame.channel] = PublishBuffer.new(frame)
         when AMQ::Protocol::Frame::Header
@@ -92,7 +99,7 @@ module AMQProxy
         else
           src_channel = frame.channel
           begin
-            if upstream_channel = @channel_map[frame.channel]
+            if upstream_channel = with_channel_map &.[frame.channel]?
               upstream_channel.write(frame)
             else
               # Channel::Close is sent, waiting for CloseOk
@@ -121,7 +128,7 @@ module AMQProxy
         end
       end
     rescue ex : IO::Error
-      Log.debug { "Disconnected #{ex.inspect}" }
+      Log.debug(exception: ex) { "Disconnected #{ex.inspect}" }
     else
       Log.debug { "Disconnected" }
     ensure
@@ -132,6 +139,7 @@ module AMQProxy
     # Send frame to client, channel id should already be remapped by the caller
     def write(frame : AMQ::Protocol::Frame)
       @lock.synchronize do
+        Log.trace { "Sending frame: #{frame}" }
         case frame
         when AMQ::Protocol::Frame::BytesBody
           # Upstream might send large frames, split them to support lower client frame_max
@@ -149,9 +157,9 @@ module AMQProxy
       end
       case frame
       when AMQ::Protocol::Frame::Channel::Close
-        @channel_map[frame.channel] = nil
+        with_channel_map &.[frame.channel] = nil
       when AMQ::Protocol::Frame::Channel::CloseOk
-        @channel_map.delete(frame.channel)
+        with_channel_map &.delete(frame.channel)
       when AMQ::Protocol::Frame::Connection::CloseOk
         @socket.close rescue nil
       end
@@ -174,13 +182,15 @@ module AMQProxy
     end
 
     private def close_all_upstream_channels(code = 500_u16, reason = "CLIENT_DISCONNECTED")
-      @channel_map.each_value do |upstream_channel|
-        upstream_channel.try &.close(code, reason)
-      rescue Upstream::WriteError
-        Log.debug { "Upstream write error while closing client's channels" }
-        next # Nothing to do
+      with_channel_map do |channel_map|
+        channel_map.each_value do |upstream_channel|
+          upstream_channel.try &.close(code, reason)
+        rescue Upstream::WriteError
+          Log.debug { "Upstream write error while closing client's channels" }
+          next # Nothing to do
+        end
+        channel_map.clear
       end
-      @channel_map.clear
     end
 
     private def expect_more_frames?(frame) : Bool
@@ -221,6 +231,7 @@ module AMQProxy
         socket.write AMQ::Protocol::PROTOCOL_START_0_9_1.to_slice
         socket.flush
         socket.close
+        Log.debug { "Invalid protocol start: #{proto}" }
         raise IO::EOFError.new("Invalid protocol start")
       end
 
diff --git a/src/amqproxy/http_server.cr b/src/amqproxy/http_server.cr
index 5e6db22..cd97802 100644
--- a/src/amqproxy/http_server.cr
+++ b/src/amqproxy/http_server.cr
@@ -22,7 +22,6 @@ module AMQProxy
         end
       end
       bind_tcp
-      spawn @http.listen, name: "HTTP Server"
       Log.info { "HTTP server listening on #{@address}:#{@port}" }
     end
 
@@ -31,6 +30,10 @@ module AMQProxy
       Log.info { "Bound to #{addr}" }
     end
 
+    def listen
+      @http.listen
+    end
+
     def metrics(context)
       writer = PrometheusWriter.new(context.response, "amqproxy")
       writer.write({name:   "identity_info",
diff --git a/src/amqproxy/server.cr b/src/amqproxy/server.cr
index 92af3e9..320daa9 100644
--- a/src/amqproxy/server.cr
+++ b/src/amqproxy/server.cr
@@ -12,6 +12,8 @@ module AMQProxy
     @clients_lock = Mutex.new
     @clients = Array(Client).new
 
+    @channel_pools_lock = Mutex.new
+
     def self.new(url : URI)
       tls = url.scheme == "amqps"
       host = url.host || "127.0.0.1"
@@ -29,12 +31,18 @@ module AMQProxy
       Log.info { "Proxy upstream: #{upstream_host}:#{upstream_port} #{upstream_tls ? "TLS" : ""}" }
     end
 
+    private def with_channel_pools(&)
+      @channel_pools_lock.synchronize do
+        yield @channel_pools
+      end
+    end
+
     def client_connections
       @clients.size
     end
 
     def upstream_connections
-      @channel_pools.each_value.sum &.connections
+      with_channel_pools &.each_value.sum(&.connections)
     end
 
     def listen(address, port)
@@ -43,10 +51,11 @@ module AMQProxy
 
     def listen(@server : TCPServer)
       Log.info { "Proxy listening on #{server.local_address}" }
+
       while socket = server.accept?
         begin
-          addr = socket.remote_address
-          spawn handle_connection(socket, addr), name: "Client#read_loop #{addr}"
+          Log.debug { "Accepted new client from #{socket.remote_address} (#{socket.inspect})" }
+          handle_connection(socket)
         rescue IO::Error
           next
         end
@@ -72,18 +81,22 @@ module AMQProxy
       end
     end
 
-    private def handle_connection(socket, remote_address)
-      c = Client.new(socket)
-      active_client(c) do
-        channel_pool = @channel_pools[c.credentials]
-        c.read_loop(channel_pool)
+    private def handle_connection(socket)
+      spawn(name: "Client #{socket.remote_address}") do
+        c = Client.new(socket)
+        channel_pool = with_channel_pools &.[c.credentials]
+        remote_address = socket.remote_address
+        Log.debug { "Client created for #{remote_address}" }
+        active_client(c) do
+          c.read_loop(channel_pool)
+        end
+      rescue IO::EOFError
+        # Client closed connection before/while negotiating
+      rescue ex # only raise from constructor, when negotating
+        Log.debug(exception: ex) { "Client negotiation failure (#{remote_address}) #{ex.inspect}" }
+      ensure
+        socket.close rescue nil
       end
-    rescue IO::EOFError
-      # Client closed connection before/while negotiating
-    rescue ex # only raise from constructor, when negotating
-      Log.debug(exception: ex) { "Client negotiation failure (#{remote_address}) #{ex.inspect}" }
-    ensure
-      socket.close rescue nil
     end
 
     private def active_client(client, &)
diff --git a/src/amqproxy/upstream.cr b/src/amqproxy/upstream.cr
index 2b840c8..31c6777 100644
--- a/src/amqproxy/upstream.cr
+++ b/src/amqproxy/upstream.cr
@@ -9,7 +9,6 @@ module AMQProxy
     Log = ::Log.for(self)
     @socket : IO
     @channels = Hash(UInt16, DownstreamChannel).new
-    @channels_lock = Mutex.new
     @channel_max : UInt16
     @lock = Mutex.new
     @remote_address : String
@@ -45,10 +44,10 @@ module AMQProxy
     end
 
     private def create_upstream_channel(downstream_channel : DownstreamChannel)
-      @channels_lock.synchronize do
+      with_channels do |channels|
         1_u16.upto(@channel_max) do |i|
-          unless @channels.has_key?(i)
-            @channels[i] = downstream_channel
+          unless channels.has_key?(i)
+            channels[i] = downstream_channel
             return UpstreamChannel.new(self, i)
           end
         end
@@ -56,12 +55,16 @@ module AMQProxy
       end
     end
 
+    private def with_channels(&)
+      yield @channels
+    end
+
     def close_channel(id, code, reason)
       send AMQ::Protocol::Frame::Channel::Close.new(id, code, reason, 0_u16, 0_u16)
     end
 
     def channels
-      @channels.size
+      with_channels &.size
     end
 
     # Frames from upstream (to client)
@@ -86,15 +89,15 @@ module AMQProxy
         when AMQ::Protocol::Frame::Channel::OpenOk # assume it always succeeds
         when AMQ::Protocol::Frame::Channel::Close
           send AMQ::Protocol::Frame::Channel::CloseOk.new(frame.channel)
-          if downstream_channel = @channels_lock.synchronize { @channels.delete(frame.channel) }
+          if downstream_channel = with_channels &.delete(frame.channel)
             downstream_channel.write frame
           end
         when AMQ::Protocol::Frame::Channel::CloseOk # when client requested channel close
-          if downstream_channel = @channels_lock.synchronize { @channels.delete(frame.channel) }
+          if downstream_channel = with_channels &.delete(frame.channel)
             downstream_channel.write(frame)
           end
         else
-          if downstream_channel = @channels_lock.synchronize { @channels[frame.channel]? }
+          if downstream_channel = with_channels &.[frame.channel]?
             downstream_channel.write(frame)
           else
             Log.debug { "Frame for unmapped channel from upstream: #{frame}" }
@@ -114,21 +117,21 @@ module AMQProxy
     end
 
     private def close_all_client_channels(code = 500_u16, reason = "UPSTREAM_ERROR")
-      @channels_lock.synchronize do
-        return if @channels.empty?
-        Log.debug { "Upstream connection closed, closing #{@channels.size} client channels" }
-        @channels.each_value do |downstream_channel|
+      with_channels do |channels|
+        return if channels.empty?
+        Log.debug { "Upstream connection closed, closing #{channels.size} client channels" }
+        channels.each_value do |downstream_channel|
           downstream_channel.close(code, reason)
         end
-        @channels.clear
+        channels.clear
       end
     end
 
     private def send_to_all_clients(frame : AMQ::Protocol::Frame::Connection)
       Log.debug { "Sending broadcast frame to all client connections" }
       clients = Set(Client).new
-      @channels_lock.synchronize do
-        @channels.each_value do |downstream_channel|
+      with_channels do |channels|
+        channels.each_value do |downstream_channel|
           clients << downstream_channel.client
         end
       end
@@ -144,9 +147,7 @@ module AMQProxy
         raise "Connection frames should not be sent through here: #{frame}"
       when AMQ::Protocol::Frame::Channel::CloseOk
         # when upstream server requested a channel close and client confirmed
-        @channels_lock.synchronize do
-          @channels.delete(frame.channel)
-        end
+        with_channels &.delete(frame.channel)
       end
       send frame
     end