Make StatsD configurable

Agent StatsD server is now configurable using the new `enable_statsd`
config option. It's disabled by default.

.changesets/add-new-config-option-to-enable-disable-statsd.md

@@ -0,0 +1,5 @@
+---
+bump: "patch"
+---
+
+Add new config option to enable/disable StatsD server in the AppSignal agent. This new config option is called `enable_statsd` and is set to `false` by default. If set to `true`, the AppSignal agent will start a StatsD server on port 8125 on the host.

lib/appsignal/config.ex

@@ -10,6 +10,7 @@ defmodule Appsignal.Config do
     dns_servers: [],
     enable_host_metrics: true,
     enable_minutely_probes: true,
+    enable_statsd: false,
     endpoint: "https://push.appsignal.com",
     diagnose_endpoint: "https://appsignal.com/diag",
     env: :dev,
@@ -196,6 +197,7 @@ defmodule Appsignal.Config do
     "APPSIGNAL_WORKING_DIRECTORY_PATH" => :working_directory_path,
     "APPSIGNAL_ENABLE_HOST_METRICS" => :enable_host_metrics,
     "APPSIGNAL_ENABLE_MINUTELY_PROBES" => :enable_minutely_probes,
+    "APPSIGNAL_ENABLE_STATSD" => :enable_statsd,
     "APPSIGNAL_SKIP_SESSION_DATA" => :skip_session_data,
     "APPSIGNAL_TRANSACTION_DEBUG_MODE" => :transaction_debug_mode,
     "APPSIGNAL_FILES_WORLD_ACCESSIBLE" => :files_world_accessible,
@@ -213,6 +215,7 @@ defmodule Appsignal.Config do
     APPSIGNAL_ENABLE_ALLOCATION_TRACKING APPSIGNAL_ENABLE_GC_INSTRUMENTATION APPSIGNAL_RUNNING_IN_CONTAINER
     APPSIGNAL_ENABLE_HOST_METRICS APPSIGNAL_SKIP_SESSION_DATA APPSIGNAL_TRANSACTION_DEBUG_MODE
     APPSIGNAL_FILES_WORLD_ACCESSIBLE APPSIGNAL_SEND_PARAMS APPSIGNAL_ENABLE_MINUTELY_PROBES
+    APPSIGNAL_ENABLE_STATSD
   )
   @atom_keys ~w(APPSIGNAL_APP_ENV APPSIGNAL_OTP_APP)
   @string_list_keys ~w(

test/appsignal/config_test.exs

@@ -194,6 +194,10 @@ defmodule Appsignal.ConfigTest do
                with_config(%{enable_minutely_probes: false}, &init_config/0)
     end
 
+    test "enable_statsd" do
+      assert %{enable_statsd: true} = with_config(%{enable_statsd: true}, &init_config/0)
+    end
+
     test "endpoint" do
       assert %{endpoint: "https://push.staging.lol"} =
                with_config(%{endpoint: "https://push.staging.lol"}, &init_config/0)
@@ -429,6 +433,13 @@ defmodule Appsignal.ConfigTest do
              ) == default_configuration() |> Map.put(:enable_minutely_probes, false)
     end
 
+    test "enable_statsd" do
+      assert with_env(
+               %{"APPSIGNAL_ENABLE_STATSD" => "true"},
+               &init_config/0
+             ) == default_configuration() |> Map.put(:enable_statsd, true)
+    end
+
     test "endpoint" do
       assert with_env(
                %{"APPSIGNAL_PUSH_API_ENDPOINT" => "https://push.staging.lol"},
@@ -949,6 +960,7 @@ defmodule Appsignal.ConfigTest do
       dns_servers: [],
       enable_host_metrics: true,
       enable_minutely_probes: true,
+      enable_statsd: false,
       endpoint: "https://push.appsignal.com",
       diagnose_endpoint: "https://appsignal.com/diag",
       env: :dev,