背景
初學filebeat和logstash，於是根據官方文檔，做了個最簡單的filebeat採集日誌，然後輸出到logstash的最簡配置。本以爲可以愉快的輸出“helloworld”的…
問題
啓動配置好的filebeat和logstash，正想見證奇蹟的時刻，沒想到logstash啓動完之後，緊接着給我來個當頭棒喝，拋了下面一個很長的異常：
io.netty.handler.codec.DecoderException: org.logstash.beats.BeatsParser$InvalidFrameProtocolException: Invalid Frame Type, received: 69
at io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:472) ~[netty-all-4.1.30.Final.jar:4.1.30.Final]
at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:278) ~[netty-all-4.1.30.Final.jar:4.1.30.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362) ~[netty-all-4.1.30.Final.jar:4.1.30.Final]
at io.netty.channel.AbstractChannelHandlerContext.access$600(AbstractChannelHandlerContext.java:38) ~[netty-all-4.1.30.Final.jar:4.1.30.Final]
at io.netty.channel.AbstractChannelHandlerContext$7.run(AbstractChannelHandlerContext.java:353) ~[netty-all-4.1.30.Final.jar:4.1.30.Final]
at io.netty.util.concurrent.DefaultEventExecutor.run(DefaultEventExecutor.java:66) ~[netty-all-4.1.30.Final.jar:4.1.30.Final]
at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:897) [netty-all-4.1.30.Final.jar:4.1.30.Final]
at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30) [netty-all-4.1.30.Final.jar:4.1.30.Final]
at java.lang.Thread.run(Thread.java:834) [?:?]
Caused by: org.logstash.beats.BeatsParser$InvalidFrameProtocolException: Invalid Frame Type, received: 69
at org.logstash.beats.BeatsParser.decode(BeatsParser.java:92) ~[logstash-input-beats-6.0.0.jar:?]
at io.netty.handler.codec.ByteToMessageDecoder.decodeRemovalReentryProtection(ByteToMessageDecoder.java:502) ~[netty-all-4.1.30.Final.jar:4.1.30.Final]
at io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:441) ~[netty-all-4.1.30.Final.jar:4.1.30.Final]
... 8 more
////////////////////////////此處省略一些異常////////////////////////////////////
[INFO ] 2020-03-03 10:39:29.943 [defaultEventExecutorGroup-4-1] BeatsHandler - [local: 127.0.0.1:5044, remote: 127.0.0.1:44356] Handling exception: org.logstash.beats.BeatsParser$InvalidFrameProtocolException: Invalid Frame Type, received: 84
[WARN ] 2020-03-03 10:39:29.943 [nioEventLoopGroup-2-2] DefaultChannelPipeline - An exceptionCaught() event was fired, and it reached at the tail of the pipeline. It usually means the last handler in the pipeline did not handle the exception.
io.netty.handler.codec.DecoderException: org.logstash.beats.BeatsParser$InvalidFrameProtocolException: Invalid Frame Type, received: 84
at io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:472) ~[netty-all-4.1.30.Final.jar:4.1.30.Final]
at io.netty.handler.codec.ByteToMessageDecoder.channelInputClosed(ByteToMessageDecoder.java:405) ~[netty-all-4.1.30.Final.jar:4.1.30.Final]
at io.netty.handler.codec.ByteToMessageDecoder.channelInputClosed(ByteToMessageDecoder.java:372) ~[netty-all-4.1.30.Final.jar:4.1.30.Final]
at io.netty.handler.codec.ByteToMessageDecoder.channelInactive(ByteToMessageDecoder.java:355) ~[netty-all-4.1.30.Final.jar:4.1.30.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelInactive(AbstractChannelHandlerContext.java:245) ~[netty-all-4.1.30.Final.jar:4.1.30.Final]
at io.netty.channel.AbstractChannelHandlerContext.access$300(AbstractChannelHandlerContext.java:38) ~[netty-all-4.1.30.Final.jar:4.1.30.Final]
at io.netty.channel.AbstractChannelHandlerContext$4.run(AbstractChannelHandlerContext.java:236) ~[netty-all-4.1.30.Final.jar:4.1.30.Final]
at io.netty.util.concurrent.DefaultEventExecutor.run(DefaultEventExecutor.java:66) ~[netty-all-4.1.30.Final.jar:4.1.30.Final]
at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:897) [netty-all-4.1.30.Final.jar:4.1.30.Final]
at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30) [netty-all-4.1.30.Final.jar:4.1.30.Final]
at java.lang.Thread.run(Thread.java:834) [?:?]
Caused by: org.logstash.beats.BeatsParser$InvalidFrameProtocolException: Invalid Frame Type, received: 84
at org.logstash.beats.BeatsParser.decode(BeatsParser.java:92) ~[logstash-input-beats-6.0.0.jar:?]
at io.netty.handler.codec.ByteToMessageDecoder.decodeRemovalReentryProtection(ByteToMessageDecoder.java:502) ~[netty-all-4.1.30.Final.jar:4.1.30.Final]
at io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:441) ~[netty-all-4.1.30.Final.jar:4.1.30.Final]
... 10 more
^C[WARN ] 2020-03-03 10:39:32.845 [SIGINT handler] runner - SIGINT received. Shutting down.
看到io.netty.handler.codec.DecoderException，第一感覺就是解碼出錯，於是把logstash的input的codec換了幾個試試，都是一樣的報錯！
於是沒頭緒的我，趕緊在某度搜索一番，終於在stackoverflow看到一個類似的異常，裏面看到有個回覆是這樣的：
意思是沒有在filebeat.yml裏設置logstash。當時我就不以爲然：怎麼可能呢。不過我還是去看了一眼我的filebeat.yml，這下可自己打臉了：
結果發現是自己還沒把logstash配置中的output.logstash前面的註釋符給去掉，因爲這個默認是註釋調的，我配置logstash的時候只管設置了hosts，忘了把上一截註釋打開了。
修正之後，再重新啓動filebeat，發現logstash已經可以正常接收了。
我不由得感嘆，這logstash報的這個異常也太具迷惑性了，直接把我差錯的路帶偏了，而且偏得離譜。不過事情的發生也是由於自己太粗心！