Add sample rate support

lib/statix.ex

@@ -59,7 +59,11 @@ defmodule Statix do
   end
 
   def transmit(conn, type, key, val, options \\ []) when is_binary(key) or is_list(key) do
-    Statix.Conn.transmit(conn, type, key, to_string(val), options)
+    if Keyword.get(options, :sample_rate, 1.0) >= :rand.uniform() do
+      Statix.Conn.transmit(conn, type, key, to_string(val), options)
+    else
+      :ok
+    end
   end
 
   def config(module) do

lib/statix/packet.ex

@@ -16,8 +16,9 @@ defmodule Statix.Packet do
   end
 
   def build(header, name, key, val, options) do
-    [header, key, ?:, val, ?| , metric_type(name)]
-    |> set_tags_option(options[:tags])
+    [header, key, ?:, val,  ?|,  metric_type(name)]
+    |> set_option(:sample_rate, options[:sample_rate])
+    |> set_option(:tags, options[:tags])
   end
 
   metrics = %{
@@ -31,11 +32,15 @@ defmodule Statix.Packet do
     defp metric_type(unquote(name)), do: unquote(type)
   end
 
-  defp set_tags_option(packet, nil) do
+  defp set_option(packet, _kind, nil) do
     packet
   end
 
-  defp set_tags_option(packet, tags) do
+  defp set_option(packet, :sample_rate, sample_rate) do
+    [packet | ["|@", :erlang.float_to_binary(sample_rate, [:compact, decimals: 2])]]
+  end
+
+  defp set_option(packet, :tags, tags) do
     [packet | ["|#", Enum.join(tags, ",")]]
   end
 end

test/statix_test.exs

@@ -46,6 +46,11 @@ defmodule StatixTest do
     Sample.increment("sample", 3, tags: ["foo:bar", "baz"])
     assert_receive {:server, "sample:3|c|#foo:bar,baz"}
 
+    Sample.increment("sample", 3, sample_rate: 1.0, tags: ["foo", "bar"])
+    assert_receive {:server, "sample:3|c|@1.0|#foo,bar"}
+
+    Sample.increment("sample", 3, sample_rate: 0.0)
+
     refute_received _any
   end
 
@@ -61,6 +66,11 @@ defmodule StatixTest do
 
     Sample.decrement("sample", 3, tags: ["foo:bar", "baz"])
     assert_receive {:server, "sample:-3|c|#foo:bar,baz"}
+    Sample.decrement("sample", 3, sample_rate: 1.0, tags: ["foo", "bar"])
+
+    assert_receive {:server, "sample:-3|c|@1.0|#foo,bar"}
+
+    Sample.decrement("sample", 3, sample_rate: 0.0)
 
     refute_received _any
   end
@@ -75,6 +85,11 @@ defmodule StatixTest do
     Sample.gauge("sample", 3, tags: ["foo:bar", "baz"])
     assert_receive {:server, "sample:3|g|#foo:bar,baz"}
 
+    Sample.gauge("sample", 3, sample_rate: 1.0, tags: ["foo", "bar"])
+    assert_receive {:server, "sample:3|g|@1.0|#foo,bar"}
+
+    Sample.gauge("sample", 3, sample_rate: 0.0)
+
     refute_received _any
   end
 
@@ -88,6 +103,11 @@ defmodule StatixTest do
     Sample.histogram("sample", 3, tags: ["foo:bar", "baz"])
     assert_receive {:server, "sample:3|h|#foo:bar,baz"}
 
+    Sample.histogram("sample", 3, sample_rate: 1.0, tags: ["foo", "bar"])
+    assert_receive {:server, "sample:3|h|@1.0|#foo,bar"}
+
+    Sample.histogram("sample", 3, sample_rate: 0.0)
+
     refute_received _any
   end
 
@@ -101,10 +121,15 @@ defmodule StatixTest do
     Sample.timing("sample", 3, tags: ["foo:bar", "baz"])
     assert_receive {:server, "sample:3|ms|#foo:bar,baz"}
 
+    Sample.timing("sample", 3, sample_rate: 1.0, tags: ["foo", "bar"])
+    assert_receive {:server, "sample:3|ms|@1.0|#foo,bar"}
+
+    Sample.timing("sample", 3, sample_rate: 0.0)
+
     refute_received _any
   end
 
-  test "measure/2" do
+  test "measure/2,3" do
     expected_result = "the stuff."
     fun_result = Sample.measure(["sample"], fn ->
       :timer.sleep(100)
@@ -113,10 +138,12 @@ defmodule StatixTest do
     assert_receive {:server, <<"sample:10", _, "|ms">>}
     assert fun_result == expected_result
 
-    Sample.measure("sample", [tags: ["foo:bar", "baz"]], fn ->
+    Sample.measure("sample", [sample_rate: 1.0, tags: ["foo", "bar"]], fn ->
       :timer.sleep(100)
     end)
-    assert_receive {:server, <<"sample:10", _, "|ms|#foo:bar,baz">>}
+    assert_receive {:server, <<"sample:10", _, "|ms|@1.0|#foo,bar">>}
+
+    refute_received _any
   end
 
   test "set/2,3" do
@@ -129,6 +156,11 @@ defmodule StatixTest do
     Sample.set("sample", 3, tags: ["foo:bar", "baz"])
     assert_receive {:server, "sample:3|s|#foo:bar,baz"}
 
+    Sample.set("sample", 3, sample_rate: 1.0, tags: ["foo", "bar"])
+    assert_receive {:server, "sample:3|s|@1.0|#foo,bar"}
+
+    Sample.set("sample", 3, sample_rate: 0.0)
+
     refute_received _any
   end
 end