Logstash-output-kafka 导致CPU使用率过高

我们产线上使用 logstash-input-file 从文件抓数据，然后通过logstash-output-kafka 将数据发送到kafka，现在就是output线程使用CPU很高。
1. 环境： CT7. 
2. 版本： Logstash 5.6.9  AND logstash-output-kafka 4.0.5
3. TOP的结果：
   两个worker消耗CPU
   PID USER      PR  NI    VIRT    RES    SHR S %CPU %MEM     TIME+ COMMAND
   3714 root      20   0 4253288 769760  16332 R 86.7  4.7   3324:30 [main]>worker0
   3715 root      20   0 4253288 769760  16332 R 86.7  4.7   3320:29 [main]>worker1
4. thread dump 结果(看起来是卡在发送的encode阶段)
"[main]>worker0" #33 daemon prio=5 os_prio=0 tid=0x00007f344021e000 nid=0xe82 runnable [0x00007f344e92f000]
   java.lang.Thread.State: RUNNABLE
        at java.lang.StringCoding$StringEncoder.encode(StringCoding.java:304)
        at java.lang.StringCoding.encode(StringCoding.java:344)
        at java.lang.String.getBytes(String.java:918)
        at org.apache.kafka.common.serialization.StringSerializer.serialize(StringSerializer.java:43)
        at org.apache.kafka.common.serialization.StringSerializer.serialize(StringSerializer.java:24)
        at org.apache.kafka.clients.producer.KafkaProducer.doSend(KafkaProducer.java:453)
        at org.apache.kafka.clients.producer.KafkaProducer.send(KafkaProducer.java:430)
        at org.apache.kafka.clients.producer.KafkaProducer.send(KafkaProducer.java:353)
        at sun.reflect.GeneratedMethodAccessor49.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)
        at org.jruby.javasupport.JavaMethod.invokeDirectWithExceptionHandling(JavaMethod.java:451)
        at org.jruby.javasupport.JavaMethod.invokeDirect(JavaMethod.java:312)
        at org.jruby.java.invokers.InstanceMethodInvoker.call(InstanceMethodInvoker.java:45)
        at org.jruby.runtime.callsite.CachingCallSite.call(CachingCallSite.java:168)
        at rubyjit.LogStash::Outputs::Kafka$$retrying_send_01d07881566e5bd041a791dccd6743425c81cea8589431969.chained_1_rescue_2$RUBY$SYNTHETIC__file__(/usr/share/logstash/vendor/bundle/jruby/1.9/gems/logstash-output-kafka-5.1.11/lib/logstash/outputs/kafka.rb:258)
        at rubyjit.LogStash::Outputs::Kafka$$retrying_send_01d07881566e5bd041a791dccd6743425c81cea8589431969.block_0$RUBY$__file__(/usr/share/logstash/vendor/bundle/jruby/1.9/gems/logstash-output-kafka-5.1.11/lib/logstash/outputs/kafka.rb:256)
        at rubyjit$LogStash::Outputs::Kafka$$retrying_send_01d07881566e5bd041a791dccd6743425c81cea8589431969$block_0$RUBY$__file__.call(rubyjit$LogStash::Outputs::Kafka$$retrying_send_01d07881566e5bd041a791dccd6743425c81cea8589431969$block_0$RUBY$__file__)
        at org.jruby.runtime.CompiledBlock19.yield(CompiledBlock19.java:135)
5. 文件编码
  [root@vssj1cal001 logs]# file vssj1cal001.webex.com_access_log.2019-08-29.txt
  vssj1cal001.webex.com_access_log.2019-08-29.txt: ASCII text, with very long lines
 
现在我知道问题可能是数据的编码问题，但是我不知道该如何排查，我检查了读取文件的除了有一些大的event之外，还没看出来有啥问题，请教一下我改如何排查这个问题，谢谢！