Merge pull request rails#55092 from francesco-loreti/add_render_json_to_health

Add render json to health

Author: rafaelfranca

actionpack/CHANGELOG.md

@@ -1,3 +1,19 @@
+*   Add JSON support to the built-in health controller.
+
+    The health controller now responds to JSON requests with a structured response
+    containing status and timestamp information. This makes it easier for monitoring
+    tools and load balancers to consume health check data programmatically.
+
+    ```ruby
+    # /up.json
+    {
+      "status": "up",
+      "timestamp": "2025-09-19T12:00:00Z"
+    }
+    ```
+
+    *Francesco Loreti*, *Juan Vásquez*
+
 *   Allow to open source file with a crash from the browser.
 
     *Igor Kasyanchuk*

railties/lib/rails/health_controller.rb

@@ -43,11 +43,17 @@ def show
 
     private
       def render_up
-        render html: html_status(color: "green")
+        respond_to do |format|
+          format.html { render html: html_status(color: "green") }
+          format.json { render json: { status: "up", timestamp: Time.current.iso8601 } }
+        end
       end
 
       def render_down
-        render html: html_status(color: "red"), status: 500
+        respond_to do |format|
+          format.html { render html: html_status(color: "red"), status: 500 }
+          format.json { render json: { status: "down", timestamp: Time.current.iso8601 }, status: 500 }
+        end
       end
 
       def html_status(color:)

railties/test/rails_health_controller_test.rb

@@ -12,20 +12,47 @@ def setup
     @routes = Rails.application.routes
   end
 
-  test "health controller renders green success page" do
-    get :show
+  test "health controller renders green success page in HTML" do
+    get :show, format: :html
     assert_response :success
     assert_match(/background-color: green/, @response.body)
   end
 
-  test "health controller renders red internal server error page" do
+  test "health controller renders red internal server error page in HTML" do
     @controller.instance_eval do
       def render_up
         raise Exception, "some exception"
       end
     end
-    get :show
+    get :show, format: :html
     assert_response :internal_server_error
     assert_match(/background-color: red/, @response.body)
   end
+
+  test "health controller returns JSON success response" do
+    get :show, format: :json
+    assert_response :success
+    assert_includes @response.content_type, "application/json"
+
+    json_response = JSON.parse(@response.body)
+    assert_equal "up", json_response["status"]
+    assert_includes json_response, "timestamp"
+    assert_match(/\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}/, json_response["timestamp"])
+  end
+
+  test "health controller returns JSON error response" do
+    @controller.instance_eval do
+      def render_up
+        raise Exception, "some exception"
+      end
+    end
+    get :show, format: :json
+    assert_response :internal_server_error
+    assert_includes @response.content_type, "application/json"
+
+    json_response = JSON.parse(@response.body)
+    assert_equal "down", json_response["status"]
+    assert_includes json_response, "timestamp"
+    assert_match(/\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}/, json_response["timestamp"])
+  end
 end