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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.

Akinori MUSHA 9 years ago
parent
feeb3d8903
commit
b095317e4c
3 changed files with 72 additions and 3 deletions
Show Diff Stats
  1. 41 1
      app/models/agents/post_agent.rb
  2. 11 0
      db/migrate/20160405072512_post_agent_set_event_header_style.rb
  3. 20 2
      spec/models/agents/post_agent_spec.rb

+ 41 - 1
app/models/agents/post_agent.rb
View File 

@@ -25,6 +25,13 @@ module Agents
25 25
26 26 
       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
27 27 
       will be attempted by this Agent, so the Event's "body" value will always be raw text.
28 
+      The Event will also have a "headers" hash and a "status" integer value.
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+      Set `event_headers_style` to one of the following values to normalize the keys of "headers" for downstream agents' convenience:
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+
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+        * `capitalized` (default) - Header names are capitalized; e.g. "Content-Type"
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+        * `downcased` - Header names are downcased; e.g. "content-type"
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+        * `snakecased` - Header names are snakecased; e.g. "content_type"
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+        * `raw` - Backward compatibility option to leave them unmodified from what the underlying HTTP library returns.
28 35
29 36 
       Other Options:
30 37 
 
@@ -92,6 +99,12 @@ module Agents
92 99 
         errors.add(:base, "if provided, emit_events must be true or false")
93 100 
       end
94 101
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+      begin
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+        normalize_response_headers({})
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+      rescue ArgumentError => e
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+        errors.add(:base, e.message)
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+      end
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+
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       unless %w[post get put delete patch].include?(method)
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         errors.add(:base, "method must be 'post', 'get', 'put', 'delete', or 'patch'")
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       end
 
@@ -124,6 +137,29 @@ module Agents
124 137
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     private
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+    def normalize_response_headers(headers)
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+      case interpolated['event_headers_style']
142 
+      when nil, '', 'capitalized'
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+        normalize = ->name {
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+          name.gsub(/(?:\A|(?<=-))([[:alpha:]])|([[:alpha:]]+)/) {
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+            $1 ? $1.upcase : $2.downcase
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+          }
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+        }
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+      when 'downcased'
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+        normalize = :downcase.to_proc
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+      when 'snakecased', nil
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+        normalize = ->name { name.tr('A-Z-', 'a-z_') }
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+      when 'raw'
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+        normalize = ->name { name }  # :itself.to_proc in Ruby >= 2.2
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+      else
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+        raise ArgumentError, "if provided, event_headers_style must be 'capitalized', 'downcased', 'snakecased' or 'raw'"
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+      end
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+
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+      headers.each_with_object({}) { |(key, value), hash|
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+        hash[normalize[key]] = value
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+      }
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+    end
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+
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     def handle(data, payload = {})
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       url = interpolated(payload)[:post_url]
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       headers = headers()
 
@@ -156,7 +192,11 @@ module Agents
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       }
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       if boolify(interpolated['emit_events'])
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-        create_event payload: { body: response.body, headers: response.headers, status: response.status }
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+        create_event payload: {
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+          body: response.body,
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+          headers: normalize_response_headers(response.headers),
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+          status: response.status
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+        }
160 200 
       end
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     end
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   end

+ 11 - 0
db/migrate/20160405072512_post_agent_set_event_header_style.rb
View File 

@@ -0,0 +1,11 @@
1 
+class PostAgentSetEventHeaderStyle < ActiveRecord::Migration
2 
+  def up
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+    Agent.of_type("Agents::PostAgent").each do |post_agent|
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+      if post_agent.send(:boolify, post_agent.options['emit_events']) &&
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+         !post_agent.options.key?('event_headers_style')
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+        post_agent.options['event_headers_style'] = 'raw'
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+        post_agent.save!
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+      end
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+    end
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+  end
11 
+end

+ 20 - 2
spec/models/agents/post_agent_spec.rb
View File 

@@ -52,7 +52,7 @@ describe Agents::PostAgent do
52 52 
           raise "unexpected Content-Type: #{content_type}"
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         end
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       end
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-      { status: 200, body: "<html>a webpage!</html>", headers: { 'Content-Type' => 'text/html' } }
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+      { status: 200, body: "<html>a webpage!</html>", headers: { 'Content-type' => 'text/html' } }
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     }
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   end
58 58 
 
@@ -226,10 +226,28 @@ describe Agents::PostAgent do
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           expect(@checker.events.last.payload['body']).to eq '<html>a webpage!</html>'
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         end
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-        it "emits the response headers" do
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+        it "emits the response headers capitalized by default" do
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           @checker.check
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           expect(@checker.events.last.payload['headers']).to eq({ 'Content-Type' => 'text/html' })
232 232 
         end
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+
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+        it "emits the response headers capitalized" do
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+          @checker.options['event_headers_style'] = 'capitalized'
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+          @checker.check
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+          expect(@checker.events.last.payload['headers']).to eq({ 'Content-Type' => 'text/html' })
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+        end
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+
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+        it "emits the response headers downcased" do
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+          @checker.options['event_headers_style'] = 'downcased'
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+          @checker.check
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+          expect(@checker.events.last.payload['headers']).to eq({ 'content-type' => 'text/html' })
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+        end
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+
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+        it "emits the response headers snakecased" do
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+          @checker.options['event_headers_style'] = 'snakecased'
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+          @checker.check
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+          expect(@checker.events.last.payload['headers']).to eq({ 'content_type' => 'text/html' })
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+        end
233 251 
       end
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     end
235 253 
   end