Add option to return default value if endpoint errored for json_endpo…

…int. (#106)

The current behavior is to terminate after a number of consecutive errors. With this option enabled consul-templaterb will not terminate, and return a default value instead. This is done with additional property because many users may already rely on the default behavior.

Co-authored-by: a.chuzhynov <[email protected]>

TemplateAPI.md

@@ -631,11 +631,12 @@ secret('secret/foo', [force_ttl: intInSecond])
 
 ## remote_resource
 
-### as_json(url, default_value, [refresh_delay_secs: intInSecond])
+### as_json(url, default_value, [refresh_delay_secs: intInSecond, default_value_on_error: bool])
 
 Fetch json data from any url. This allows to create templates with consul/vault data mixed in with data coming from other services/api.
 Polling interval can be controlled with `refresh_delay_secs` option.
 Request method (`GET`, `POST`, ...) can be controlled with `request_method` option.
+To return default value on the case of error, set `default_value_on_error` to true.
 
 ```erb
 remote_resource.as_json('http://my-api.dev/fridge/list.json', [])

lib/consul/async/consul_template.rb

@@ -29,14 +29,14 @@ def initialize(endpoints_manager)
         @endp_manager = endpoints_manager
       end
 
-      def as_json(url, default_value, refresh_delay_secs: 10, **opts)
+      def as_json(url, default_value, refresh_delay_secs: 10, default_value_on_error: false, **opts)
         conf = JSONConfiguration.new(url: url, min_duration: refresh_delay_secs, retry_on_non_diff: refresh_delay_secs, **opts)
         endpoint_id = url + opts.hash.to_s
         @endp_manager.create_if_missing(url, {}, endpoint_id: endpoint_id) do
           if default_value.is_a?(Array)
-            ConsulTemplateJSONArray.new(JSONEndpoint.new(conf, url, default_value))
+            ConsulTemplateJSONArray.new(JSONEndpoint.new(conf, url, default_value, default_value_on_error: default_value_on_error))
           else
-            ConsulTemplateJSONObject.new(JSONEndpoint.new(conf, url, default_value))
+            ConsulTemplateJSONObject.new(JSONEndpoint.new(conf, url, default_value, default_value_on_error: default_value_on_error))
           end
         end
       end

lib/consul/async/json_endpoint.rb

@@ -93,9 +93,10 @@ def initialize(http, override_nil_response = nil)
     # Endpoint (aka URL) of a remote API that might be called
     class JSONEndpoint
       attr_reader :conf, :url, :queue, :stats, :last_result, :enforce_json_200, :start_time, :default_value, :query_params
-      def initialize(conf, url, default_value, enforce_json_200 = true, query_params = {})
+      def initialize(conf, url, default_value, enforce_json_200: true, query_params: {}, default_value_on_error: false)
         @conf = conf.create(url)
         @default_value = default_value
+        @default_value_on_error = default_value_on_error
         @url = url
         @queue = EM::Queue.new
         @s_callbacks = []
@@ -174,7 +175,7 @@ def _handle_error(http)
         retry_in = _compute_retry_in([600, conf.retry_duration + 2**@consecutive_errors].min)
         ::Consul::Async::Debug.puts_error "[#{url}] - #{http.error} - Retry in #{retry_in}s #{stats.body_bytes_human}"
         @consecutive_errors += 1
-        http_result = HttpResponse.new(http)
+        http_result = @default_value_on_error ? HttpResponse.new(http, @default_value.to_json) : HttpResponse.new(http)
         EventMachine.add_timer(retry_in) do
           yield
           queue.push(Object.new)
@@ -203,6 +204,7 @@ def fetch
           http = connection[:conn].send(request_method, build_request)
           http.callback do
             if enforce_json_200 && !(200..299).cover?(http.response_header.status) && http.response_header['Content-Type'] != 'application/json'
+              handle_default_on_error(http) if @default_value_on_error
               _handle_error(http) do
                 warn "[RETRY][#{url}] (#{@consecutive_errors} errors)" if (@consecutive_errors % 10) == 1
               end
@@ -227,6 +229,7 @@ def fetch
           end
 
           http.errback do
+            handle_default_on_error(http) if @default_value_on_error
             unless @stopping
               _handle_error(http) do
                 if (@consecutive_errors % 10) == 1
@@ -243,6 +246,15 @@ def fetch
         end
         queue.pop(&cb)
       end
+
+      def handle_default_on_error(http)
+        ::Consul::Async::Debug.puts_error "[#{url}] response status #{http.response_header.status}; using default value"
+        @consecutive_errors = 0
+        json_result = JSONResult.new(@default_value.to_json, false, HttpResponse.new(http, ''), stats, 10, fake: true)
+        @last_result = json_result
+        @ready = true
+        @s_callbacks.each { |c| c.call(json_result) }
+      end
     end
   end
 end

spec/consul/async/json_endpoint_spec.rb

@@ -7,8 +7,8 @@
 
 RSpec.describe Consul::Async do
   context 'default parameters' do
-    it 'request 200' do
-      mock_url = 'http://perfectly.working.url'
+    it 'response 200' do
+      mock_url = 'http://working.url'
       conf = Consul::Async::JSONConfiguration.new(url: mock_url)
       default_value = '[]'
 
@@ -23,7 +23,7 @@
       expect(json_endpoint.last_result.data).to eq(response_body.to_json)
     end
 
-    it 'request 500' do
+    it 'response 500' do
       mock_url = 'http://error.working.url'
       conf = Consul::Async::JSONConfiguration.new(url: mock_url)
       default_value = ''
@@ -52,4 +52,68 @@
       expect(json_endpoint.last_result.retry_in).to be_positive
     end
   end
+
+  context 'when default_value_on_error on' do
+    let(:default_value_on_error) { true }
+    context 'when response 500' do
+      it 'return default value' do
+        mock_url = 'http://not.working.url'
+        conf = Consul::Async::JSONConfiguration.new(url: mock_url, min_duration: 10, retry_on_non_diff: 20)
+        default_value = '["default", "value"]'
+
+        json_endpoint = nil
+        stub_request(:get, mock_url)
+          .to_return(body: '', status: 500)
+        EM.run_block do
+          json_endpoint = Consul::Async::JSONEndpoint.new(conf, mock_url, default_value, default_value_on_error: default_value_on_error)
+        end
+        EM.run_block do
+          expect(json_endpoint.ready?).to eq(true)
+          expect(json_endpoint.last_result.data).to eq(default_value.to_json)
+          expect(json_endpoint.last_result.retry_in).to be_positive
+        end
+      end
+    end
+
+    context 'when address is not reachable' do
+      it 'return default value' do
+        mock_url = 'http://not.working.url'
+        conf = Consul::Async::JSONConfiguration.new(url: mock_url, min_duration: 10, retry_on_non_diff: 20)
+        default_value = '["default", "value"]'
+
+        json_endpoint = nil
+        stub_request(:get, mock_url).to_timeout
+        EM.run_block do
+          json_endpoint = Consul::Async::JSONEndpoint.new(conf, mock_url, default_value, default_value_on_error: default_value_on_error)
+        end
+        EM.run_block do
+          expect(json_endpoint.ready?).to eq(true)
+          expect(json_endpoint.last_result.data).to eq(default_value.to_json)
+          expect(json_endpoint.last_result.retry_in).to be_positive
+        end
+      end
+    end
+
+    context 'when response 200' do
+      it 'return value from endpoint' do
+        mock_url = 'http://working.url'
+        conf = Consul::Async::JSONConfiguration.new(url: mock_url, min_duration: 10, retry_on_non_diff: 20)
+        default_value = '["default", "value"]'
+        endpoint_body = '{"a": "b"}'
+
+        json_endpoint = nil
+        stub_request(:get, mock_url)
+          .to_return(body: endpoint_body, status: 200)
+
+        EM.run_block do
+          json_endpoint = Consul::Async::JSONEndpoint.new(conf, mock_url, default_value, default_value_on_error: default_value_on_error)
+        end
+        EM.run_block do
+          expect(json_endpoint.ready?).to eq(true)
+          expect(json_endpoint.last_result.data.to_json).to eq(endpoint_body.to_json)
+          expect(json_endpoint.last_result.retry_in).to be_positive
+        end
+      end
+    end
+  end
 end