Add high priority fields to beginning of JSON object when json format

CHANGELOG.md

@@ -5,6 +5,8 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 
 ## [unreleased]
 
+- Add high priority fields (timestamp, level, level index and message) to beginning of JSON object output when using JSON formatter to ensure log entries are parsable even when JSON logs are mangled
+
 ## [4.17.0]
 
 - Correct `source_code_uri` URL

lib/semantic_logger/formatters/raw.rb

@@ -117,19 +117,19 @@ def call(log, logger)
         self.log    = log
         self.logger = logger
 
+        time
+        level
+        message
         host
         application
         environment
-        time
-        level
         pid
         thread_name
         file_name_and_line
         duration
         tags
         named_tags
         name
-        message
         payload
         exception
         metric

test/formatters/json_test.rb

@@ -0,0 +1,45 @@
+require_relative "../test_helper"
+
+module SemanticLogger
+  module Formatters
+    class JsonTest < Minitest::Test
+      describe Json do
+        let(:log_time) do
+          Time.utc(2017, 1, 14, 8, 32, 5.375276)
+        end
+
+        let(:level) do
+          :debug
+        end
+
+        let(:log) do
+          log      = SemanticLogger::Log.new("JsonTest", level)
+          log.time = log_time
+          log
+        end
+
+        let(:expected_time) do
+          SemanticLogger::Formatters::Base::PRECISION == 3 ? "2017-01-14T08:32:05.375Z" : "2017-01-14T08:32:05.375276Z"
+        end
+
+        let(:formatter) do
+          formatter = SemanticLogger::Formatters::Json.new(log_host: false)
+          # Does not use the logger instance for formatting purposes
+          formatter.call(log, nil)
+          formatter
+        end
+
+        describe "call" do
+          it "sets timestamp, level, level_index, and message at the beginning of the JSON object" do
+            log.message = "Some message"
+            expected_start = %({"timestamp":"#{expected_time}","level":"debug","level_index":1,"message":"Some message")
+
+            is_starting_with_high_priority_fields = formatter.call(log, nil).start_with?(expected_start)
+
+            assert is_starting_with_high_priority_fields, "Expected #{formatter.call(log, nil)} to start with #{expected_start}"
+          end
+        end
+      end
+    end
+  end
+end