Add half_open_resource_timeout for net http

.rubocop.yml

@@ -42,6 +42,8 @@ Metrics/MethodLength:
 
 Metrics/ClassLength:
   Max: 500
+  Exclude:
+    - test/**/*
 
 Metrics/AbcSize:
   Max: 50

README.md

@@ -431,7 +431,7 @@ There are three configuration parameters for circuit breakers in Semian:
   again.
 * **success_threshold**. The amount of successes on the circuit until closing it
   again, that is to start accepting all requests to the circuit.
-* **half_open_resource_timeout**. Timeout for the resource in seconds when the circuit is half-open (only supported for MySQL).
+* **half_open_resource_timeout**. Timeout for the resource in seconds when the circuit is half-open (only supported for MySQL and Net::HTTP).
 
 ### Bulkheading
 

lib/semian/circuit_breaker.rb

@@ -125,15 +125,14 @@ def disabled?
     end
 
     def maybe_with_half_open_resource_timeout(resource, &block)
-      result = nil
-
-      if half_open? && @half_open_resource_timeout && resource.respond_to?(:with_resource_timeout)
-        resource.with_resource_timeout(@half_open_resource_timeout) do
-          result = block.call
+      result =
+        if half_open? && @half_open_resource_timeout && resource.respond_to?(:with_resource_timeout)
+          resource.with_resource_timeout(@half_open_resource_timeout) do
+            block.call
+          end
+        else
+          block.call
         end
-      else
-        result = block.call
-      end
 
       result
     end

lib/semian/net_http.rb

@@ -90,6 +90,19 @@ def transport_request(*)
       end
     end
 
+    def with_resource_timeout(timeout)
+      prev_read_timeout = read_timeout
+      prev_open_timeout = open_timeout
+      begin
+        self.read_timeout = timeout
+        self.open_timeout = timeout
+        yield
+      ensure
+        self.read_timeout = prev_read_timeout
+        self.open_timeout = prev_open_timeout
+      end
+    end
+
     private
 
     def handle_error_responses(result)

test/net_http_test.rb

@@ -42,6 +42,42 @@ def test_semian_identifier
     end
   end
 
+  def test_changes_timeout_when_half_open_and_configured
+    http = Net::HTTP.new(SemianConfig['toxiproxy_upstream_host'], SemianConfig['http_toxiproxy_port'])
+    expected_read_timeout = http.read_timeout
+    expected_open_timeout = http.open_timeout
+    options = proc do |host, port|
+      {
+        tickets: 3,
+        success_threshold: 2,
+        error_threshold: 2,
+        error_timeout: 10,
+        open_circuit_server_errors: true,
+        name: "#{host}_#{port}",
+        half_open_resource_timeout: 1,
+      }
+    end
+
+    with_semian_configuration(options) do
+      with_server do
+        Toxiproxy['semian_test_net_http'].downstream(:latency, latency: 2000).apply do
+          http.get('/200')
+        end
+
+        half_open_cicuit!
+
+        Toxiproxy['semian_test_net_http'].downstream(:latency, latency: 2000).apply do
+          assert_raises Net::ReadTimeout do
+            http.get('/200')
+          end
+        end
+      end
+    end
+
+    assert_equal expected_read_timeout, http.read_timeout
+    assert_equal expected_open_timeout, http.open_timeout
+  end
+
   def test_trigger_open
     with_semian_configuration do
       with_server do
@@ -396,6 +432,12 @@ def test_persistent_state_after_server_restart
 
   private
 
+  def half_open_cicuit!(backwards_time_travel = 10)
+    Timecop.travel(Time.now - backwards_time_travel) do
+      open_circuit!
+    end
+  end
+
   def with_semian_configuration(options = DEFAULT_SEMIAN_CONFIGURATION)
     orig_semian_options = Semian::NetHTTP.semian_configuration
     Semian::NetHTTP.instance_variable_set(:@semian_configuration, nil)