Added X-Request-Id tracking and TaggedLogging to easily log that and other production concerns

2 files changed, 48 insertions, 0 deletions

diff --git a/actionpack/lib/action_dispatch/http/request.rb b/actionpack/lib/action_dispatch/http/request.rb
index 37d0a3e0b8..7a5237dcf3 100644
--- a/actionpack/lib/action_dispatch/http/request.rb
+++ b/actionpack/lib/action_dispatch/http/request.rb
@@ -177,6 +177,16 @@ module ActionDispatch
       @remote_ip ||= (@env["action_dispatch.remote_ip"] || ip).to_s
     end
 
+    # Returns the unique request id, which is based off either the X-Request-Id header that can
+    # be generated by a firewall, load balancer, or web server or by the RequestId middleware
+    # (which sets the action_dispatch.request_id environment variable).
+    #
+    # This unique ID is useful for tracing a request from end-to-end as part of logging or debugging.
+    # This relies on the rack variable set by the ActionDispatch::RequestId middleware.
+    def uuid
+      @uuid ||= env["action_dispatch.request_id"]
+    end
+
     # Returns the lowercase name of the HTTP server software.
     def server_software
       (@env['SERVER_SOFTWARE'] && /^([a-zA-Z]+)/ =~ @env['SERVER_SOFTWARE']) ? $1.downcase : nil
diff --git a/actionpack/lib/action_dispatch/middleware/request_id.rb b/actionpack/lib/action_dispatch/middleware/request_id.rb
new file mode 100644
index 0000000000..968ad6c28d
--- /dev/null
+++ b/actionpack/lib/action_dispatch/middleware/request_id.rb
@@ -0,0 +1,38 @@
+require 'digest/md5'
+
+module ActionDispatch
+  # Makes a unique request id available to the action_dispatch.request_id env variable (which is then accessible through
+  # ActionDispatch::Request#uuid) and sends the same id to the client via the X-Request-Id header.
+  #
+  # The unique request id is either based off the X-Request-Id header in the request, which would typically be generated
+  # by a firewall, load balancer, or the web server, or, if this header is not available, a random uuid. If the
+  # header is accepted from the outside world, we sanitize it to a max of 255 chars and alphanumeric and dashes only.
+  #
+  # The unique request id can be used to trace a request end-to-end and would typically end up being part of log files
+  # from multiple pieces of the stack.
+  class RequestId
+    def initialize(app)
+      @app = app
+    end
+
+    def call(env)
+      env["action_dispatch.request_id"] = external_request_id(env) || internal_request_id
+
+      status, headers, body = @app.call(env)
+
+      headers["X-Request-Id"] = env["action_dispatch.request_id"]
+      [ status, headers, body ]
+    end
+    
+    private
+      def external_request_id(env)
+        if env["HTTP_X_REQUEST_ID"].present?
+          env["HTTP_X_REQUEST_ID"].gsub(/[^\w\d\-]/, "").first(255)
+        end
+      end
+    
+      def internal_request_id
+        SecureRandom.uuid
+      end
+  end
+end