Allow PostAgent headers to interpolate event data (#1606)

app/models/agents/post_agent.rb

@@ -122,17 +122,19 @@ module Agents
 
     def receive(incoming_events)
       incoming_events.each do |event|
-        outgoing = interpolated(event)['payload'].presence || {}
-        if boolify(interpolated['no_merge'])
-          handle outgoing, event.payload
-        else
-          handle outgoing.merge(event.payload), event.payload
+        interpolate_with(event) do
+          outgoing = interpolated['payload'].presence || {}
+          if boolify(interpolated['no_merge'])
+            handle outgoing, event.payload, headers(interpolated[:headers])
+          else
+            handle outgoing.merge(event.payload), event.payload, headers(interpolated[:headers])
+          end
         end
       end
     end
 
     def check
-      handle interpolated['payload'].presence || {}
+      handle interpolated['payload'].presence || {}, headers
     end
 
     private
@@ -160,9 +162,8 @@ module Agents
       }
     end
 
-    def handle(data, payload = {})
+    def handle(data, payload = {}, headers)
       url = interpolated(payload)[:post_url]
-      headers = headers()
 
       case method
       when 'get', 'delete'

spec/models/agents/post_agent_spec.rb

@@ -33,7 +33,7 @@ describe Agents::PostAgent do
     stub_request(:any, /:/).to_return { |request|
       method = request.method
       @requests += 1
-      @sent_requests[method] << req = OpenStruct.new(uri: request.uri)
+      @sent_requests[method] << req = OpenStruct.new(uri: request.uri, headers: request.headers)
       case method
       when :get, :delete
         req.data = request.uri.query
@@ -137,6 +137,18 @@ describe Agents::PostAgent do
       expect(uri.path).to eq('/a_variable')
       expect(uri.query).to eq("existing_param=existing_value")
     end
+
+    it "interpolates outgoing headers with the event payload" do
+      @checker.options['headers'] = {
+        "Foo" => "{{ variable }}"
+      }
+      @event.payload = {
+        'variable' => 'a_variable'
+      }
+      @checker.receive([@event])
+      headers = @sent_requests[:post].first.headers
+      expect(headers["Foo"]).to eq("a_variable")
+    end
   end
 
   describe "#check" do
@@ -199,6 +211,15 @@ describe Agents::PostAgent do
       expect(@sent_requests[:post][0].data).to eq('<test>hello</test>')
     end
 
+    it "interpolates outgoing headers" do
+      @checker.options['headers'] = {
+        "Foo" => "{% credential aws_key %}"
+      }
+      @checker.check
+      headers = @sent_requests[:post].first.headers
+      expect(headers["Foo"]).to eq("2222222222-jane")
+    end
+
     describe "emitting events" do
       context "when emit_events is not set to true" do
         it "does not emit events" do