add support for service checks

lib/custom_functions.ex

@@ -81,6 +81,11 @@ defmodule Instruments.CustomFunctions do
       def measure(key, options \\ [], func) do
         Instruments.measure([unquote(prefix_with_dot), key], options, func)
       end
+
+      @doc false
+      def send_service_check(key, status, options \\ []) do
+        Instruments.send_service_check([unquote(prefix_with_dot), key], status, options)
+      end
     end
   end
 end

lib/instruments.ex

@@ -214,6 +214,79 @@ defmodule Instruments do
     end
   end
 
+  @doc """
+  Sends a service check to DataDog
+
+  Reports the health status of a service. Status must be one of:
+  `:ok` (0), `:warning` (1), `:critical` (2), or `:unknown` (3).
+
+  ## Options
+
+    * `tags` - A list of String tags
+    * `message` - A description of the current status
+    * `hostname` - The hostname to associate with the check
+    * `timestamp` - A Unix timestamp for the check
+
+  ## Examples
+
+      Instruments.send_service_check("my.service", :ok)
+      Instruments.send_service_check("my.service", :critical,
+        tags: ["env:prod"],
+        message: "connection refused",
+        hostname: "web-01",
+        timestamp: 1234567890
+      )
+
+  """
+  defmacro send_service_check(name_ast, status, opts \\ []) do
+    name_iodata = MacroHelpers.to_iolist(name_ast, __CALLER__)
+
+    quote do
+      status_code =
+        case unquote(status) do
+          :ok -> "0"
+          :warning -> "1"
+          :critical -> "2"
+          :unknown -> "3"
+        end
+
+      header = ["_sc", "|", unquote(name_iodata), "|", status_code]
+
+      opts = unquote(opts)
+
+      message =
+        Enum.reduce([:timestamp, :hostname, :tags, :message], header, fn
+          :timestamp, acc ->
+            case Keyword.get(opts, :timestamp) do
+              nil -> acc
+              ts -> [acc, "|d:", Integer.to_string(ts)]
+            end
+
+          :hostname, acc ->
+            case Keyword.get(opts, :hostname) do
+              nil -> acc
+              h -> [acc, "|h:", h]
+            end
+
+          :tags, acc ->
+            case Keyword.get(opts, :tags) do
+              nil -> acc
+              tag_list -> [acc, "|#", Enum.intersperse(tag_list, ",")]
+            end
+
+          :message, acc ->
+            case Keyword.get(opts, :message) do
+              nil -> acc
+              m -> [acc, "|m:", m]
+            end
+        end)
+
+      unquote(@metrics_module)
+      |> Process.whereis()
+      |> :gen_udp.send(Instruments.statsd_host(), Instruments.statsd_port(), message)
+    end
+  end
+
   @doc false
   def flush_all_probes(wait_for_flush \\ true, flush_timeout_ms \\ 10_000) do
     Probe.Supervisor

lib/macro_helpers.ex

@@ -3,7 +3,7 @@ defmodule Instruments.MacroHelpers do
 
   alias Instruments.RateTracker
 
-  @safe_metric_types [:increment, :decrement, :gauge, :event, :set]
+  @safe_metric_types [:increment, :decrement, :gauge, :event, :set, :service_check]
 
   @metrics_module Application.get_env(:instruments, :reporter_module, Instruments.Statix)
 

test/custom_functions_test.exs

@@ -83,6 +83,14 @@ defmodule Instruments.CustomFunctionsTest do
 
       assert_metric_reported(:timing, "custom.my.measure", 10..11, tags: ["timing:short"])
     end
+
+    test "to send_service_check calls" do
+      Custom.send_service_check("my.check", :ok)
+      assert_metric_reported(:service_check, "custom.my.check", :ok)
+
+      Custom.send_service_check("my.check", :critical, tags: ["env:prod"])
+      assert_metric_reported(:service_check, "custom.my.check", :critical, tags: ["env:prod"])
+    end
   end
 
   test "setting a runtime prefix" do

test/instruments_test.exs

@@ -137,6 +137,36 @@ defmodule InstrumentsTest do
     assert_metric_reported(:event, "my_title", "my text", tags: ["host:any", "another:tag"])
   end
 
+  test "sending service checks" do
+    Instruments.send_service_check("my.service", :ok)
+    assert_metric_reported(:service_check, "my.service", :ok)
+
+    Instruments.send_service_check("my.service", :warning)
+    assert_metric_reported(:service_check, "my.service", :warning)
+
+    Instruments.send_service_check("my.service", :critical)
+    assert_metric_reported(:service_check, "my.service", :critical)
+
+    Instruments.send_service_check("my.service", :unknown)
+    assert_metric_reported(:service_check, "my.service", :unknown)
+  end
+
+  test "sending service checks with all options" do
+    Instruments.send_service_check("my.service", :critical,
+      timestamp: 1_234_567_890,
+      hostname: "web-01",
+      tags: ["env:prod"],
+      message: "connection refused"
+    )
+
+    assert_metric_reported(:service_check, "my.service", :critical,
+      timestamp: 1_234_567_890,
+      hostname: "web-01",
+      tags: ["env:prod"],
+      message: "connection refused"
+    )
+  end
+
   test "sending events with a title that's a variable blows up" do
     quoted =
       quote do

test/support/fake_statsd.ex

@@ -28,6 +28,19 @@ defmodule FakeStatsd do
     |> do_decode
   end
 
+  defp do_decode(["_sc", name, status | rest]) do
+    status_atom =
+      case status do
+        "0" -> :ok
+        "1" -> :warning
+        "2" -> :critical
+        "3" -> :unknown
+      end
+
+    opts = decode_service_check_metadata(rest)
+    {:service_check, name, status_atom, opts}
+  end
+
   defp do_decode([name_and_val, type | rest]) do
     opts = decode_tags_and_sampling(rest)
     {name, val} = decode_name_and_value(name_and_val)
@@ -109,4 +122,27 @@ defmodule FakeStatsd do
         end
     end
   end
+
+  defp decode_service_check_metadata(fields),
+    do: decode_service_check_metadata(fields, [])
+
+  defp decode_service_check_metadata([], accum), do: Enum.reverse(accum)
+
+  defp decode_service_check_metadata([<<"d:", ts::binary>> | rest], accum) do
+    {timestamp, ""} = Integer.parse(ts)
+    decode_service_check_metadata(rest, Keyword.put(accum, :timestamp, timestamp))
+  end
+
+  defp decode_service_check_metadata([<<"h:", hostname::binary>> | rest], accum) do
+    decode_service_check_metadata(rest, Keyword.put(accum, :hostname, hostname))
+  end
+
+  defp decode_service_check_metadata([<<"#", tags::binary>> | rest], accum) do
+    tag_list = String.split(tags, ",")
+    decode_service_check_metadata(rest, Keyword.put(accum, :tags, tag_list))
+  end
+
+  defp decode_service_check_metadata([<<"m:", message::binary>> | rest], accum) do
+    decode_service_check_metadata(rest, Keyword.put(accum, :message, message))
+  end
 end

test/test_helper.exs

@@ -1,7 +1,7 @@
 ExUnit.start()
 
 defmodule MetricsAssertions do
-  @safe_metric_types [:increment, :decrement, :gauge, :event, :set]
+  @safe_metric_types [:increment, :decrement, :gauge, :event, :set, :service_check]
   use ExUnit.Case
 
   def assert_metric_reported(metric_type, metric_name) do