Log errors for messages that exceed the maximum size

lib/segment/analytics/defaults.rb

@@ -17,6 +17,10 @@ module Queue
         MAX_SIZE = 10000
       end
 
+      module Message
+        MAX_BYTES = 32768 # 32Kb
+      end
+
       module BackoffPolicy
         MIN_TIMEOUT_MS = 100
         MAX_TIMEOUT_MS = 10000

lib/segment/analytics/message.rb

@@ -0,0 +1,22 @@
+require 'segment/analytics/defaults'
+
+module Segment
+  class Analytics
+    # Represents a message to be sent to the API
+    class Message
+      def initialize(hash)
+        @hash = hash
+      end
+
+      def too_big?
+        to_json.bytesize > Defaults::Message::MAX_BYTES
+      end
+
+      # Since the hash is expected to not be modified (set at initialization),
+      # the JSON version can be cached after the first computation.
+      def to_json(*args)
+        @json ||= @hash.to_json(*args)
+      end
+    end
+  end
+end

lib/segment/analytics/message_batch.rb

@@ -0,0 +1,28 @@
+require 'segment/analytics/logging'
+
+module Segment
+  class Analytics
+    # A batch of `Message`s to be sent to the API
+    class MessageBatch
+      extend Forwardable
+      include Segment::Analytics::Logging
+
+      def initialize
+        @messages = []
+      end
+
+      def <<(message)
+        if message.too_big?
+          logger.error('a message exceeded the maximum allowed size')
+        else
+          @messages << message
+        end
+      end
+
+      def_delegators :@messages, :to_json
+      def_delegators :@messages, :clear
+      def_delegators :@messages, :empty?
+      def_delegators :@messages, :length
+    end
+  end
+end

lib/segment/analytics/worker.rb

@@ -1,7 +1,8 @@
 require 'segment/analytics/defaults'
-require 'segment/analytics/utils'
-require 'segment/analytics/defaults'
+require 'segment/analytics/message'
+require 'segment/analytics/message_batch'
 require 'segment/analytics/request'
+require 'segment/analytics/utils'
 
 module Segment
   class Analytics
@@ -26,7 +27,7 @@ def initialize(queue, write_key, options = {})
         @write_key = write_key
         @batch_size = options[:batch_size] || Queue::BATCH_SIZE
         @on_error = options[:on_error] || proc { |status, error| }
-        @batch = []
+        @batch = MessageBatch.new
         @lock = Mutex.new
       end
 
@@ -38,7 +39,7 @@ def run
 
           @lock.synchronize do
             until @batch.length >= @batch_size || @queue.empty?
-              @batch << @queue.pop
+              @batch << Message.new(@queue.pop)
             end
           end
 

spec/segment/analytics/message_batch_spec.rb

@@ -0,0 +1,25 @@
+require 'spec_helper'
+
+module Segment
+  class Analytics
+    describe MessageBatch do
+      describe '#<<' do
+        subject { described_class.new }
+
+        it 'appends messages' do
+          subject << Message.new('a' => 'b')
+          expect(subject.length).to eq(1)
+        end
+
+        it 'rejects messages that exceed the maximum allowed size' do
+          max_bytes = Segment::Analytics::Defaults::Message::MAX_BYTES
+          hash = { 'a' => 'b' * max_bytes }
+          message = Message.new(hash)
+
+          subject << message
+          expect(subject.length).to eq(0)
+        end
+      end
+    end
+  end
+end

spec/segment/analytics/message_spec.rb

@@ -0,0 +1,35 @@
+require 'spec_helper'
+
+module Segment
+  class Analytics
+    describe Message do
+      describe '#to_json' do
+        it 'caches JSON conversions' do
+          # Keeps track of the number of times to_json was called
+          nested_obj = Class.new do
+            attr_reader :to_json_call_count
+
+            def initialize
+              @to_json_call_count = 0
+            end
+
+            def to_json(*_)
+              @to_json_call_count += 1
+              '{}'
+            end
+          end.new
+
+          message = Message.new('some_key' => nested_obj)
+          expect(nested_obj.to_json_call_count).to eq(0)
+
+          message.to_json
+          expect(nested_obj.to_json_call_count).to eq(1)
+
+          # When called a second time, the call count shouldn't increase
+          message.to_json
+          expect(nested_obj.to_json_call_count).to eq(1)
+        end
+      end
+    end
+  end
+end