Warn on missing backend only.

lib/metrics/backend.rb

@@ -3,11 +3,17 @@
 # Released under the MIT License.
 # Copyright, 2021-2023, by Samuel Williams.
 
+require 'console/event/failure'
+
 module Metrics
 	# Require a specific trace backend.
 	def self.require_backend(env = ENV)
-		if path = env['METRICS_BACKEND']
-			require(path)
+		if backend = env['METRICS_BACKEND']
+			begin
+				require(backend)
+			rescue LoadError => error
+				::Console::Event::Failure.for(error).emit(self, "Unable to load metrics backend!", backend: backend, severity: :warn)
+			end
 
 			Metrics.extend(Backend::Interface)
 		end

test/metrics/backend.rb

@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+# Released under the MIT License.
+# Copyright, 2022-2023, by Samuel Williams.
+
+require "metrics/backend"
+require "json"
+
+require "sus/fixtures/console"
+
+describe Metrics do
+	with ".require_backend" do
+		include_context Sus::Fixtures::Console::CapturedLogger
+
+		it "logs a warning if backend cannot be loaded" do
+			subject.require_backend({"METRICS_BACKEND" => "metrics/backend/missing"})
+
+			expect_console.to have_logged(
+				severity: be == :warn,
+			)
+		end
+	end
+end