add Prometheus metrics

Gemfile

@@ -14,6 +14,8 @@ gem "cuid2"
 gem "jwt"
 gem "httparty"
 
+gem "prometheus-client"
+
 group :development do
   gem "ruby-lsp"
   gem "rack-test"

Gemfile.lock

@@ -33,6 +33,8 @@ GEM
       ast (~> 2.4.1)
       racc
     prism (1.4.0)
+    prometheus-client (4.2.5)
+      base64
     puma (6.6.0)
       nio4r (~> 2.0)
     racc (1.8.1)
@@ -136,6 +138,7 @@ DEPENDENCIES
   ksuid
   minitest
   nanoid
+  prometheus-client
   puma
   rack-test
   rake

app.rb

@@ -23,6 +23,14 @@ $LOAD_PATH.unshift File.dirname(__FILE__) + "/lib"
 
 require "config"
 
+require "rack"
+require "prometheus/middleware/collector"
+require "prometheus/middleware/exporter"
+
+use Rack::Deflater
+use Prometheus::Middleware::Collector
+use Prometheus::Middleware::Exporter
+
 VERSION = "0.2.3"
 
 CHUNK_SIZE = 1024**2