logstash消费kafka数据，根据ID写入hdfs的对应路径下

开发新需求，需要消费kafka的数据，根据业务主键ID写入到对应的hdfs路径下

最开始实验的logstash为7.4版本，发现和本地的kafka版本不对应，报错信息：broker may not be available，后来查看logstash版本，发现需要使用logstash2.4版本才可以和本地的kafka0.9版本对应

日志的格式为：

2020-06-11 11:02:02.632 -- {"gradeId":"2","role":"STUDENT","userStatus":1,"data":{"publishExamClassId":"47c50966f34b41cf819358d077691cce","examSubmitType":2,"examQuestionCount":41,"questionResultSet":[{"questionId":"xl_a543bbe2ca1e4b8e8029c1148ed34abf_v4","originalQueType":11,"questionResult":"1","questionType":1,"userAnswerContent":"["1"]"},{"questionId":"xl_4367b003c0a14d2390470b89ece9184e_v4","originalQueType":11,"questionResult":"1","questionType":1,"userAnswerContent":"["3"]"}],"examSubmitTime":1591843564000,"examId":203877,"unifyType":1,"examRightQuestionCount":32,"subjectId":"010","questionAnswerTime":0},"actId":"3000005","classId":"47c50966f34b41cf819358d077691cce","countyId":"421024","schoolId":"154986","localIp":"10.0.183.13","userIp":"","originCode":"1","functionModule":"exam","time":1591844522631,"userIcon":"00000000000000000000000000000000"}

包含两部分：前面为时间字符串 ，后面为json串，通过 -- 进行的链接，需要根据后半部分json串中的examId写入到hdfs中对应的目录下

切换到logstash2.4版本后，研究了对应filter参数，最后的实际配置为：

input{
#  stdin{
     # codec=>rubydebug
#        }
    kafka {
        zk_cOnnect=>"SANDBOX-HADOOP-02.xuele.net"
        topic_id=>"exam_log"
        codec => plain
    }

}
filter{
    mutate{
        split=>["message"," -- "]
        add_field => {
            "field2" => "%{[message][1]}"
        }
    }
    json{
        source => "field2"
        add_field => {
            "field3" => "%{data}"
        }
    }
    json{
        source => "field3"
    }
    mutate {
        join => ["message", " -- "]
    }
}
output{
    webhdfs {
        host => "SANDBOX-HADOOP-01.xuele.net"
        port => 50070
        user => "bigdata"
        path => "/test/%{examId}/%{examSubmitTime}"
        codec => line {
            format => "%{message}"
        }
    }
#  stdout{
#        codec=>rubydebug
#  }
}

在之上配置的基础上，还需要做出对应修改，例如日期格式需要通过date参数进行格式化

而且输出的codec中需要加上：

codec => line {
            format => "%{message}"
        }

不然会在落地的文件内容前加上默认的时间戳

另附logstash和kafka的版本对应信息：