Add support for global tags (lexmag#19)

lib/statix.ex

@@ -49,6 +49,8 @@ defmodule Statix do
       Defaults to `"127.0.0.1"`.
     * `:port` - (integer) the port (on `:host`) where the StatsD-compatible
       server is running. Defaults to `8125`.
+    * `:tags` - ([binary]) a list of global tags that will be sent with all
+      metrics. By default this option is not present.
 
   By default, the configuration is evaluated once, at compile time. If you plan
   on changing the configuration at runtime, you must specify the
@@ -347,7 +349,7 @@ defmodule Statix do
     sample_rate = Keyword.get(options, :sample_rate)
 
     if is_nil(sample_rate) or sample_rate >= :rand.uniform() do
-      Conn.transmit(conn, type, key, to_string(val), options)
+      Conn.transmit(conn, type, key, to_string(val), put_global_tags(conn.sock, options))
     else
       :ok
     end
@@ -376,4 +378,16 @@ defmodule Statix do
       {_p1, _p2} -> [part1, ?., part2, ?.]
     end
   end
+
+  defp put_global_tags(module, options) do
+    conn_tags =
+      :statix
+      |> Application.get_env(module, [])
+      |> Keyword.get(:tags, [])
+
+    app_tags = Application.get_env(:statix, :tags, [])
+    global_tags = conn_tags ++ app_tags
+
+    Keyword.update(options, :tags, global_tags, &(&1 ++ global_tags))
+  end
 end

lib/statix/packet.ex

@@ -44,6 +44,8 @@ defmodule Statix.Packet do
     [packet | ["|@", :erlang.float_to_binary(sample_rate, [:compact, decimals: 2])]]
   end
 
+  defp set_option(packet, :tags, []), do: packet
+
   defp set_option(packet, :tags, tags) when is_list(tags) do
     [packet | ["|#", Enum.join(tags, ",")]]
   end

test/statix_test.exs

@@ -244,4 +244,28 @@ defmodule StatixTest do
     OverridingStatix.set("sample", 3, tags: ["foo"])
     assert_receive {:server, "sample-overridden:3|s|#foo"}
   end
+
+  test "sends global tags when present" do
+    Application.put_env(:statix, :tags, ["tag:test"])
+
+    TestStatix.increment("sample", 3)
+    assert_receive {:server, "sample:3|c|#tag:test"}
+
+    TestStatix.increment("sample", 3, tags: ["foo"])
+    assert_receive {:server, "sample:3|c|#foo,tag:test"}
+  after
+    Application.delete_env(:statix, :tags)
+  end
+
+  test "sends global connection-specific tags" do
+    Application.put_env(:statix, TestStatix, tags: ["tag:test"])
+
+    TestStatix.increment("sample", 3)
+    assert_receive {:server, "sample:3|c|#tag:test"}
+
+    TestStatix.increment("sample", 3, tags: ["foo"])
+    assert_receive {:server, "sample:3|c|#foo,tag:test"}
+  after
+    Application.delete_env(:statix, TestStatix)
+  end
 end