feature: conditional per request timeout setting

README.markdown

@@ -58,6 +58,20 @@ require "rack-timeout"
 use Rack::Timeout, service_timeout: 5
 ```
 
+### Conditional timeout
+
+You can set a conditional timeout per request.
+Although make sure to always meet your requirements (e.g. Heroku 30s timeout) in all cases.
+If the block returns `nil` or `false`, timeout will be disabled for this request.
+
+```ruby
+# set conditional_timeout to a callable block
+# config/initializers/rack_timeout.rb
+Rack::Timeout.conditional_timeout = proc { |env| env["PATH_INFO"] =~ /^\/admin/ ? 20 : 5 }
+
+# equivalent for Sinatra/Rack apps
+use Rack::Timeout, conditional_timeout: ->(env) { env["PATH_INFO"] =~ /^\/admin/ ? 20 : 5 }
+```
 
 The Rabbit Hole
 ---------------

lib/rack/timeout/core.rb

@@ -58,16 +58,18 @@ def read_timeout_property value, default
     end
 
     attr_reader \
-      :service_timeout,   # How long the application can take to complete handling the request once it's passed down to it.
-      :wait_timeout,      # How long the request is allowed to have waited before reaching rack. If exceeded, the request is 'expired', i.e. dropped entirely without being passed down to the application.
-      :wait_overtime,     # Additional time over @wait_timeout for requests with a body, like POST requests. These may take longer to be received by the server before being passed down to the application, but should not be expired.
-      :service_past_wait  # when false, reduces the request's computed timeout from the service_timeout value if the complete request lifetime (wait + service) would have been longer than wait_timeout (+ wait_overtime when applicable). When true, always uses the service_timeout value. we default to false under the assumption that the router would drop a request that's not responded within wait_timeout, thus being there no point in servicing beyond seconds_service_left (see code further down) up until service_timeout.
-
-    def initialize(app, service_timeout:nil, wait_timeout:nil, wait_overtime:nil, service_past_wait:false)
-      @service_timeout   = read_timeout_property service_timeout, 15
-      @wait_timeout      = read_timeout_property wait_timeout,    30
-      @wait_overtime     = read_timeout_property wait_overtime,   60
-      @service_past_wait = service_past_wait
+      :service_timeout,    # How long the application can take to complete handling the request once it's passed down to it.
+      :wait_timeout,       # How long the request is allowed to have waited before reaching rack. If exceeded, the request is 'expired', i.e. dropped entirely without being passed down to the application.
+      :wait_overtime,      # Additional time over @wait_timeout for requests with a body, like POST requests. These may take longer to be received by the server before being passed down to the application, but should not be expired.
+      :service_past_wait,  # when false, reduces the request's computed timeout from the service_timeout value if the complete request lifetime (wait + service) would have been longer than wait_timeout (+ wait_overtime when applicable). When true, always uses the service_timeout value. we default to false under the assumption that the router would drop a request that's not responded within wait_timeout, thus being there no point in servicing beyond seconds_service_left (see code further down) up until service_timeout.
+      :conditional_timeout # service_timeout is determined on the fly, evaluating the given block in the middleware context
+
+    def initialize(app, service_timeout:nil, wait_timeout:nil, wait_overtime:nil, service_past_wait:false, conditional_timeout:nil)
+      @service_timeout     = read_timeout_property service_timeout, 15
+      @wait_timeout        = read_timeout_property wait_timeout,    30
+      @wait_overtime       = read_timeout_property wait_overtime,   60
+      @service_past_wait   = service_past_wait
+      @conditional_timeout = conditional_timeout
       @app = app
     end
 
@@ -96,6 +98,9 @@ def call(env)
         end
       end
 
+      # set service timeout from configuration or by calling conditional_timeout block with env
+      service_timeout = conditional_timeout.respond_to?(:call) ? conditional_timeout.call(env) : self.service_timeout
+
       # pass request through if service_timeout is false (i.e., don't time it out at all.)
       return @app.call(env) unless service_timeout
 

lib/rack/timeout/legacy.rb

@@ -8,14 +8,15 @@
 module Rack::Timeout::ClassLevelProperties
 
   module ClassMethods
-    attr_accessor :service_timeout, :wait_timeout, :wait_overtime, :service_past_wait
+    attr_accessor :service_timeout, :wait_timeout, :wait_overtime, :service_past_wait, :conditional_timeout
     alias_method :timeout=, :service_timeout=
 
     [ :service_timeout=,
       :timeout=,
       :wait_timeout=,
       :wait_overtime=,
       :service_past_wait=,
+      :conditional_timeout=
     ].each do |isetter|
       setter = instance_method(isetter)
       define_method(isetter) do |x|
@@ -31,6 +32,10 @@ module InstanceMethods
       define_method(m) { read_timeout_property self.class.send(m), super() }
     end
 
+    def conditional_timeout
+      self.class.conditional_timeout || super
+    end
+
     def service_past_wait
       self.class.service_past_wait || super
     end