Log the original event to the error_flow if Flow#write raises an error

lib/rackstash/flow.rb

@@ -345,7 +345,7 @@ module Rackstash
           @adapter.write @encoder.encode(event)
           true
         rescue Exception => exception
-          log_error("write failed for adapter #{adapter.inspect}", exception)
+          log_error("write failed for adapter #{adapter.inspect}", exception, event)
           raise unless exception.is_a?(StandardError)
           raise if synchronous?
         end
@@ -354,7 +354,7 @@ module Rackstash
 
     private
 
-    def log_error(message, exception)
+    def log_error(message, exception, event = nil)
       message = Rackstash::Message.new(message, severity: ERROR)
 
       error_event = {
@@ -366,6 +366,8 @@ module Rackstash
         FIELD_MESSAGE => [message],
         FIELD_TIMESTAMP => message.time
       }
+      error_event['event'] = event unless event.nil?
+
       error_flow.write(error_event)
     rescue
       # At this place, writing to the error log has also failed. This is a bad

spec/rackstash/flow_spec.rb

@@ -488,7 +488,8 @@ RSpec.describe Rackstash::Flow do
             'error_trace' => instance_of(String),
             'tags' => [],
             'message' => [instance_of(Rackstash::Message)],
-            '@timestamp' => instance_of(Time)
+            '@timestamp' => instance_of(Time),
+            'event' => event
           )
         expect(adapter).to receive(:write).and_raise('ERROR')
         expect { flow.write(event) }.not_to raise_error
@@ -521,7 +522,8 @@ RSpec.describe Rackstash::Flow do
             'error_trace' => instance_of(String),
             'tags' => [],
             'message' => [instance_of(Rackstash::Message)],
-            '@timestamp' => instance_of(Time)
+            '@timestamp' => instance_of(Time),
+            'event' => event
           )
         expect(adapter).to receive(:write).and_raise('ERROR')