Add an option event_headers_style to PostAgent

It is defaulted to `capitalized`, normalizing emitted headers by capitalizing the names so downstream agents don't need to bother with the letter cases. Previously, the style of header names in an emitted event would vary depending on the server and the backend HTTP library. Most notably, the `net_http` backend downcases header names whereas other backends do not. For backward compatibility, preexisting PostAgents are automatically configured to have `event_headers_style` set to `raw` via migration.
huginn · Apr 5, 2016 · dce5bfc · dce5bfc
1 parent feeb3d8
commit dce5bfc
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Showing 3 changed files with 76 additions and 3 deletions.
diff --git a/app/models/agents/post_agent.rb b/app/models/agents/post_agent.rb
@@ -25,6 +25,13 @@ class PostAgent < Agent
 
       If `emit_events` is set to `true`, the server response will be emitted as an Event and can be fed to a WebsiteAgent for parsing (using its `data_from_event` and `type` options). No data processing
       will be attempted by this Agent, so the Event's "body" value will always be raw text.
+      The Event will also have a "headers" hash and a "status" integer value.
+      Set `event_headers_style` to one of the following values to normalize the keys of "headers" for downstream agents' convenience:
+
+        * `capitalized` (default) - Header names are capitalized; e.g. "Content-Type"
+        * `downcased` - Header names are downcased; e.g. "content-type"
+        * `snakecased` - Header names are snakecased; e.g. "content_type"
+        * `raw` - Backward compatibility option to leave them unmodified from what the underlying HTTP library returns.
 
       Other Options:
 
@@ -92,6 +99,12 @@ def validate_options
         errors.add(:base, "if provided, emit_events must be true or false")
       end
 
+      begin
+        normalize_response_headers({})
+      rescue ArgumentError => e
+        errors.add(:base, e.message)
+      end
+
       unless %w[post get put delete patch].include?(method)
         errors.add(:base, "method must be 'post', 'get', 'put', 'delete', or 'patch'")
       end
@@ -124,6 +137,33 @@ def check
 
     private
 
+    def normalize_response_headers(headers)
+      case interpolated['event_headers_style']
+      when nil, '', 'capitalized'
+        normalize = ->name {
+          name.gsub(/(?:\A|(?<=-))([[:alpha:]])|([[:alpha:]]+)/) {
+            $1 ? $1.upcase : $2.downcase
+          }
+        }
+      when 'downcased'
+        normalize = :downcase.to_proc
+      when 'snakecased', nil
+        normalize = ->name { name.tr('A-Z-', 'a-z_') }
+      when 'raw'
+        if Object.method_defined?(:itself)  # Ruby >= 2.2
+          normalize = :itself.to_proc
+        else
+          normalize = ->name { name }
+        end
+      else
+        raise ArgumentError, "if provided, event_headers_style must be 'capitalized', 'downcased', 'snakecased' or 'raw'"
+      end
+
+      headers.each_with_object({}) { |(key, value), hash|
+        hash[normalize[key]] = value
+      }
+    end
+
     def handle(data, payload = {})
       url = interpolated(payload)[:post_url]
       headers = headers()
@@ -156,7 +196,11 @@ def handle(data, payload = {})
       }
 
       if boolify(interpolated['emit_events'])
-        create_event payload: { body: response.body, headers: response.headers, status: response.status }
+        create_event payload: {
+          body: response.body,
+          headers: normalize_response_headers(response.headers),
+          status: response.status
+        }
       end
     end
   end

diff --git a/db/migrate/20160405072512_post_agent_set_event_header_style.rb b/db/migrate/20160405072512_post_agent_set_event_header_style.rb
@@ -0,0 +1,11 @@
+class PostAgentSetEventHeaderStyle < ActiveRecord::Migration
+  def up
+    Agent.of_type("Agents::PostAgent").each do |post_agent|
+      if post_agent.send(:boolify, post_agent.options['emit_events']) &&
+         !post_agent.options.key?('event_headers_style')
+        post_agent.options['event_headers_style'] = 'raw'
+        post_agent.save!
+      end
+    end
+  end
+end
diff --git a/spec/models/agents/post_agent_spec.rb b/spec/models/agents/post_agent_spec.rb
@@ -52,7 +52,7 @@
           raise "unexpected Content-Type: #{content_type}"
         end
       end
-      { status: 200, body: "<html>a webpage!</html>", headers: { 'Content-Type' => 'text/html' } }
+      { status: 200, body: "<html>a webpage!</html>", headers: { 'Content-type' => 'text/html' } }
     }
   end
 
@@ -226,10 +226,28 @@
           expect(@checker.events.last.payload['body']).to eq '<html>a webpage!</html>'
         end
 
-        it "emits the response headers" do
+        it "emits the response headers capitalized by default" do
           @checker.check
           expect(@checker.events.last.payload['headers']).to eq({ 'Content-Type' => 'text/html' })
         end
+
+        it "emits the response headers capitalized" do
+          @checker.options['event_headers_style'] = 'capitalized'
+          @checker.check
+          expect(@checker.events.last.payload['headers']).to eq({ 'Content-Type' => 'text/html' })
+        end
+
+        it "emits the response headers downcased" do
+          @checker.options['event_headers_style'] = 'downcased'
+          @checker.check
+          expect(@checker.events.last.payload['headers']).to eq({ 'content-type' => 'text/html' })
+        end
+
+        it "emits the response headers snakecased" do
+          @checker.options['event_headers_style'] = 'snakecased'
+          @checker.check
+          expect(@checker.events.last.payload['headers']).to eq({ 'content_type' => 'text/html' })
+        end
       end
     end
   end