diff --git a/lib/fluent/plugin/parser_syslog.rb b/lib/fluent/plugin/parser_syslog.rb
index a8f2182ee0..452830a31b 100644
--- a/lib/fluent/plugin/parser_syslog.rb
+++ b/lib/fluent/plugin/parser_syslog.rb
@@ -63,18 +63,23 @@ class SyslogParser < Parser
       def initialize
         super
         @mutex = Mutex.new
-        @space_count = nil
+        @regexp = nil
+        @regexp3164 = nil
+        @regexp5424 = nil
+        @regexp_parser = nil
+        @time_parser_rfc3164 = nil
+        @time_parser_rfc5424 = nil
+        @space_count_rfc3164 = nil
         @space_count_rfc5424 = nil
-        @skip_space_count = false
+        @skip_space_count_rfc3164 = false
         @skip_space_count_rfc5424 = false
+        @support_rfc5424_without_subseconds = false
+        @time_parser_rfc5424_without_subseconds = nil
       end
 
       def configure(conf)
         super
 
-        @time_parser_rfc3164 = @time_parser_rfc5424 = nil
-        @time_parser_rfc5424_without_subseconds = nil
-        @support_rfc5424_without_subseconds = false
         @regexp_parser = @parser_type == :regexp
         @regexp = case @message_format
                   when :rfc3164
@@ -87,6 +92,7 @@ class << self
                         alias_method :parse, :parse_rfc3164
                       end
                     end
+                    setup_time_parser_3164(@time_format)
                     RFC3164_WITHOUT_TIME_AND_PRI_REGEXP
                   when :rfc5424
                     if @regexp_parser
@@ -99,27 +105,37 @@ class << self
                       end
                     end
                     @time_format = @rfc5424_time_format unless conf.has_key?('time_format')
-                    @support_rfc5424_without_subseconds = true
-                    @skip_space_count_rfc5424 = @time_format.count(' ').zero?
+                    setup_time_parser_5424(@time_format)
                     RFC5424_WITHOUT_TIME_AND_PRI_REGEXP
                   when :auto
                     class << self
                       alias_method :parse, :parse_auto
                     end
-                    @time_parser_rfc3164 = time_parser_create(format: @time_format)
-                    @time_parser_rfc5424 = time_parser_create(format: @rfc5424_time_format)
-                    @skip_space_count_rfc5424 = @rfc5424_time_format.count(' ').zero?
+                    setup_time_parser_3164(@time_format)
+                    setup_time_parser_5424(@rfc5424_time_format)
                     nil
                   end
 
-        @space_count = @time_format.squeeze(' ').count(' ') + 1
-        @space_count_rfc5424 = @rfc5424_time_format.squeeze(' ').count(' ') + 1
-        @time_parser = time_parser_create
-        @time_parser_rfc5424_without_subseconds = time_parser_create(format: "%Y-%m-%dT%H:%M:%S%z")
+        if @regexp_parser
+          @regexp3164 = RFC3164_WITHOUT_TIME_AND_PRI_REGEXP
+          @regexp5424 = RFC5424_WITHOUT_TIME_AND_PRI_REGEXP
+        end
+      end
 
-        if ['%b %d %H:%M:%S', '%b %d %H:%M:%S.%N'].include?(@time_format)
-          @skip_space_count = true
+      def setup_time_parser_3164(time_fmt)
+        @time_parser_rfc3164 = time_parser_create(format: time_fmt)
+        if ['%b %d %H:%M:%S', '%b %d %H:%M:%S.%N'].include?(time_fmt)
+          @skip_space_count_rfc3164 = true
         end
+        @space_count_rfc3164 = time_fmt.squeeze(' ').count(' ') + 1
+      end
+
+      def setup_time_parser_5424(time_fmt)
+        @time_parser_rfc5424 = time_parser_create(format: time_fmt)
+        @time_parser_rfc5424_without_subseconds = time_parser_create(format: "%Y-%m-%dT%H:%M:%S%z")
+        @skip_space_count_rfc5424 = time_fmt.count(' ').zero?
+        @space_count_rfc5424 = time_fmt.squeeze(' ').count(' ') + 1
+        @support_rfc5424_without_subseconds = true
       end
 
       # this method is for tests
@@ -133,8 +149,6 @@ def parse(text)
 
       def parse_auto(text, &block)
         if REGEXP_DETECT_RFC5424.match?(text)
-          @regexp = RFC5424_WITHOUT_TIME_AND_PRI_REGEXP
-          @time_parser = @time_parser_rfc5424
           @support_rfc5424_without_subseconds = true
           if @regexp_parser
             parse_rfc5424_regex(text, &block)
@@ -142,8 +156,6 @@ def parse_auto(text, &block)
             parse_rfc5424(text, &block)
           end
         else
-          @regexp = RFC3164_WITHOUT_TIME_AND_PRI_REGEXP
-          @time_parser = @time_parser_rfc3164
           if @regexp_parser
             parse_rfc3164_regex(text, &block)
           else
@@ -171,7 +183,7 @@ def parse_rfc3164_regex(text, &block)
 
         i = idx - 1
         sq = false
-        @space_count.times do
+        @space_count_rfc3164.times do
           while text[i + 1] == SPLIT_CHAR
             sq = true
             i += 1
@@ -181,12 +193,12 @@ def parse_rfc3164_regex(text, &block)
         end
 
         time_str = sq ? text.slice(idx, i - idx).squeeze(SPLIT_CHAR) : text.slice(idx, i - idx)
-        time = @mutex.synchronize { @time_parser.parse(time_str) }
+        time = @mutex.synchronize { @time_parser_rfc3164.parse(time_str) }
         if @keep_time_key
           record['time'] = time_str
         end
 
-        parse_plain(time, text, i + 1, record, RFC3164_CAPTURES, &block)
+        parse_plain(@regexp3164, time, text, i + 1, record, RFC3164_CAPTURES, &block)
       end
 
       def parse_rfc5424_regex(text, &block)
@@ -217,7 +229,7 @@ def parse_rfc5424_regex(text, &block)
         time_str = sq ? text.slice(idx, i - idx).squeeze(SPLIT_CHAR) : text.slice(idx, i - idx)
         time = @mutex.synchronize do
           begin
-            @time_parser.parse(time_str)
+            @time_parser_rfc5424.parse(time_str)
           rescue Fluent::TimeParser::TimeParseError => e
             if @support_rfc5424_without_subseconds
               log.trace(e)
@@ -231,15 +243,15 @@ def parse_rfc5424_regex(text, &block)
         if @keep_time_key
           record['time'] = time_str
         end
-        parse_plain(time, text, i + 1, record, RFC5424_CAPTURES, &block)
+        parse_plain(@regexp5424, time, text, i + 1, record, RFC5424_CAPTURES, &block)
       end
 
       # @param time [EventTime]
       # @param idx [Integer] note: this argument is needed to avoid string creation
       # @param record [Hash]
       # @param capture_list [Array] for performance
-      def parse_plain(time, text, idx, record, capture_list, &block)
-        m = @regexp.match(text, idx)
+      def parse_plain(re, time, text, idx, record, capture_list, &block)
+        m = re.match(text, idx)
         if m.nil?
           yield nil, nil
           return
@@ -282,7 +294,7 @@ def parse_rfc3164(text, &block)
           end
         end
 
-        if @skip_space_count
+        if @skip_space_count_rfc3164
           # header part
           time_size = 15 # skip Mmm dd hh:mm:ss
           time_end = text[cursor + time_size]
@@ -301,7 +313,7 @@ def parse_rfc3164(text, &block)
         else
           i = cursor - 1
           sq = false
-          @space_count.times do
+          @space_count_rfc3164.times do
             while text[i + 1] == SPLIT_CHAR
               sq = true
               i += 1
@@ -358,7 +370,7 @@ def parse_rfc3164(text, &block)
         msg.chomp!
         record['message'] = msg
 
-        time = @time_parser.parse(time_str)
+        time = @time_parser_rfc3164.parse(time_str)
         record['time'] = time_str if @keep_time_key
 
         yield time, record
@@ -393,7 +405,7 @@ def parse_rfc5424(text, &block)
         else
           i = cursor - 1
           sq = false
-          @space_count.times do
+          @space_count_rfc5424.times do
             while text[i + 1] == SPLIT_CHAR
               sq = true
               i += 1
@@ -478,7 +490,7 @@ def parse_rfc5424(text, &block)
         end
 
         time = begin
-                 @time_parser.parse(time_str)
+                 @time_parser_rfc5424.parse(time_str)
                rescue Fluent::TimeParser::TimeParseError => e
                  if @support_rfc5424_without_subseconds
                    @time_parser_rfc5424_without_subseconds.parse(time_str)
diff --git a/test/plugin/test_parser_syslog.rb b/test/plugin/test_parser_syslog.rb
index 45cab4e597..d75aae748c 100644
--- a/test/plugin/test_parser_syslog.rb
+++ b/test/plugin/test_parser_syslog.rb
@@ -481,7 +481,6 @@ def test_auto_with_legacy_syslog_message(param)
         assert_equal(event_time("Feb 28 00:00:12", format: '%b %d %M:%S:%H'), time)
         assert_equal(@expected, record)
       end
-      assert_equal(Fluent::Plugin::SyslogParser::RFC3164_WITHOUT_TIME_AND_PRI_REGEXP, @parser.instance.patterns['format'])
     end
 
     data('regexp' => 'regexp', 'string' => 'string')
@@ -497,7 +496,6 @@ def test_auto_with_legacy_syslog_priority_message(param)
         assert_equal(event_time("Feb 28 12:00:00", format: '%b %d %M:%S:%H'), time)
         assert_equal(@expected.merge('pri' => 6), record)
       end
-      assert_equal(Fluent::Plugin::SyslogParser::RFC3164_WITHOUT_TIME_AND_PRI_REGEXP, @parser.instance.patterns['format'])
     end
 
     data('regexp' => 'regexp', 'string' => 'string')
@@ -517,7 +515,6 @@ def test_parse_with_rfc5424_message(param)
         assert_equal 16, record["pri"]
         assert_equal "Hi, from Fluentd!", record["message"]
       end
-      assert_equal(Fluent::Plugin::SyslogParser::RFC5424_WITHOUT_TIME_AND_PRI_REGEXP, @parser.instance.patterns['format'])
     end
 
     data('regexp' => 'regexp', 'string' => 'string')
@@ -537,7 +534,7 @@ def test_parse_with_rfc5424_structured_message(param)
                      record["extradata"]
         assert_equal "Hi, from Fluentd!", record["message"]
       end
-      assert_equal(Fluent::Plugin::SyslogParser::RFC5424_WITHOUT_TIME_AND_PRI_REGEXP, @parser.instance.patterns['format'])end
+    end
 
     data('regexp' => 'regexp', 'string' => 'string')
     def test_parse_with_both_message_type(param)
@@ -553,7 +550,6 @@ def test_parse_with_both_message_type(param)
         assert_equal(event_time("Feb 28 12:00:00", format: '%b %d %M:%S:%H'), time)
         assert_equal(@expected.merge('pri' => 1), record)
       end
-      assert_equal(Fluent::Plugin::SyslogParser::RFC3164_WITHOUT_TIME_AND_PRI_REGEXP, @parser.instance.patterns['format'])
 
       text = '<16>1 2017-02-06T13:14:15.003Z 192.168.0.1 fluentd 11111 ID24224 [exampleSDID@20224 iut="3" eventSource="Application" eventID="11211"] Hi, from Fluentd!'
       @parser.instance.parse(text) do |time, record|
@@ -564,21 +560,18 @@ def test_parse_with_both_message_type(param)
                      record["extradata"]
         assert_equal "Hi, from Fluentd!", record["message"]
       end
-      assert_equal(Fluent::Plugin::SyslogParser::RFC5424_WITHOUT_TIME_AND_PRI_REGEXP, @parser.instance.patterns['format'])
 
       text = '<1>Feb 28 12:00:02 192.168.0.1 fluentd[11111]: [error] Syslog test 2>1'
       @parser.instance.parse(text) do |time, record|
         assert_equal(event_time("Feb 28 12:00:02", format: '%b %d %M:%S:%H'), time)
         assert_equal(@expected.merge('pri' => 1, 'message'=> '[error] Syslog test 2>1'), record)
       end
-      assert_equal(Fluent::Plugin::SyslogParser::RFC3164_WITHOUT_TIME_AND_PRI_REGEXP, @parser.instance.patterns['format'])
 
       text = '<1>Feb 28 12:00:02 192.168.0.1 fluentd[11111]: [error] Syslog test'
       @parser.instance.parse(text) do |time, record|
         assert_equal(event_time("Feb 28 12:00:02", format: '%b %d %M:%S:%H'), time)
         assert_equal(@expected.merge('pri' => 1), record)
       end
-      assert_equal(Fluent::Plugin::SyslogParser::RFC3164_WITHOUT_TIME_AND_PRI_REGEXP, @parser.instance.patterns['format'])
 
       text = '<16>1 2017-02-06T13:14:15.003Z 192.168.0.1 fluentd - - - Hi, from Fluentd!'
       @parser.instance.parse(text) do |time, record|
@@ -588,7 +581,6 @@ def test_parse_with_both_message_type(param)
         assert_equal "-", record["extradata"]
         assert_equal "Hi, from Fluentd!", record["message"]
       end
-      assert_equal(Fluent::Plugin::SyslogParser::RFC5424_WITHOUT_TIME_AND_PRI_REGEXP, @parser.instance.patterns['format'])
     end
 
     data('regexp' => 'regexp', 'string' => 'string')
@@ -605,7 +597,6 @@ def test_parse_with_both_message_type_and_priority(param)
         assert_equal(event_time("Feb 28 12:00:00", format: '%b %d %M:%S:%H'), time)
         assert_equal(@expected.merge('pri' => 6), record)
       end
-      assert_equal(Fluent::Plugin::SyslogParser::RFC3164_WITHOUT_TIME_AND_PRI_REGEXP, @parser.instance.patterns['format'])
 
       text = '<16>1 2017-02-06T13:14:15.003Z 192.168.0.1 fluentd 11111 ID24224 [exampleSDID@20224 iut="3" eventSource="Application" eventID="11211"] Hi, from Fluentd!'
       @parser.instance.parse(text) do |time, record|
@@ -616,14 +607,12 @@ def test_parse_with_both_message_type_and_priority(param)
                      record["extradata"]
         assert_equal "Hi, from Fluentd!", record["message"]
       end
-      assert_equal(Fluent::Plugin::SyslogParser::RFC5424_WITHOUT_TIME_AND_PRI_REGEXP, @parser.instance.patterns['format'])
 
       text = '<16>Feb 28 12:00:02 192.168.0.1 fluentd[11111]: [error] Syslog test'
       @parser.instance.parse(text) do |time, record|
         assert_equal(event_time("Feb 28 12:00:02", format: '%b %d %M:%S:%H'), time)
         assert_equal(@expected.merge('pri' => 16), record)
       end
-      assert_equal(Fluent::Plugin::SyslogParser::RFC3164_WITHOUT_TIME_AND_PRI_REGEXP, @parser.instance.patterns['format'])
 
       text = '<16>1 2017-02-06T13:14:15.003Z 192.168.0.1 fluentd - - - Hi, from Fluentd!'
       @parser.instance.parse(text) do |time, record|
@@ -633,7 +622,6 @@ def test_parse_with_both_message_type_and_priority(param)
         assert_equal "-", record["extradata"]
         assert_equal "Hi, from Fluentd!", record["message"]
       end
-      assert_equal(Fluent::Plugin::SyslogParser::RFC5424_WITHOUT_TIME_AND_PRI_REGEXP, @parser.instance.patterns['format'])
 
       text = '<16>1 2017-02-06T13:14:15Z 192.168.0.1 fluentd - - - Hi, from Fluentd without subseconds!'
       @parser.instance.parse(text) do |time, record|
@@ -643,7 +631,6 @@ def test_parse_with_both_message_type_and_priority(param)
         assert_equal "-", record["extradata"]
         assert_equal "Hi, from Fluentd without subseconds!", record["message"]
       end
-      assert_equal(Fluent::Plugin::SyslogParser::RFC5424_WITHOUT_TIME_AND_PRI_REGEXP, @parser.instance.patterns['format'])
     end
   end
 end