From 21848ff91b29df14b8e78f1b1994ad2d2a671d2a Mon Sep 17 00:00:00 2001
From: Stephen Paul Weber <singpolyma@singpolyma.net>
Date: Tue, 19 Jul 2022 09:38:31 -0500
Subject: [PATCH] Log in background thread

File IO is fast, but can still block reactor.
---
 .rubocop.yml          |  1 +
 lib/background_log.rb | 29 +++++++++++++++++++++++++++++
 sgx_jmp.rb            |  4 +++-
 3 files changed, 33 insertions(+), 1 deletion(-)
 create mode 100644 lib/background_log.rb

diff --git a/.rubocop.yml b/.rubocop.yml
index 325e600..f46799f 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -29,6 +29,7 @@ Metrics/ParameterLists:
 Naming/MethodParameterName:
   AllowNamesEndingInNumbers: false
   AllowedNames:
+    - io
     - m
     - e
     - q
diff --git a/lib/background_log.rb b/lib/background_log.rb
new file mode 100644
index 0000000..617a4f1
--- /dev/null
+++ b/lib/background_log.rb
@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+
+# Subclass IO because Logger does an is_a? check
+class BackgroundLog < IO
+	def initialize(io)
+		@io = io
+		@q = Queue.new
+		thread
+		at_exit do
+			@q << :done
+			thread.join
+		end
+	end
+
+	def thread
+		@thread ||= Thread.new do
+			loop do
+				m = @q.pop
+				break if m == :done
+
+				@io.write m
+			end
+		end
+	end
+
+	def write(s)
+		@q << s
+	end
+end
diff --git a/sgx_jmp.rb b/sgx_jmp.rb
index ecd50ec..50c1764 100644
--- a/sgx_jmp.rb
+++ b/sgx_jmp.rb
@@ -14,8 +14,10 @@ require "ruby-bandwidth-iris"
 require "sentry-ruby"
 require "statsd-instrument"
 
+require_relative "lib/background_log"
+
 $stdout.sync = true
-LOG = Ougai::Logger.new($stdout)
+LOG = Ougai::Logger.new(BackgroundLog.new($stdout))
 LOG.level = ENV.fetch("LOG_LEVEL", "info")
 LOG.formatter = Ougai::Formatters::Readable.new(
 	nil,
-- 
2.38.5