【原创】大数据基础之Gobblin（2）持久化kafka到hdfs

gobblin 0.10

想要持久化kafka到hdfs有很多种方式，比如flume、logstash、gobblin，其中flume和logstash是流式的，gobblin是批处理式的，gobblin通过定时任务触发来完成数据持久化，在任务和任务之间是没有任何读写的，这点是和flume、logstash的最大不同；

gobblin有几种部署方式：

1）standalone+cron；

2）mr+oozie/azkaban等

3）docker；

其中第3中方式最为方便，因为gobblin可以把任务的状态都写到hdfs上，所以在哪个节点启动gobblin并没有什么区别，而且只有数据同步之后才会修改元数据，保证不会因为kafka或者hdfs或者自身故障导致丢数据；

1 配置

#job
job.name=test_job
job.group=test_group
job.schedule=0 0 */1 * * ?
job.lock.enabled=false

#source
source.class=gobblin.source.extractor.extract.kafka.KafkaSimpleSource
extract.namespace=gobblin.extract.kafka
kafka.brokers=$kafka_brokers
bootstrap.with.offset=latest
topic.whitelist=$kafka_topics

mr.job.max.mappers=1

#writer
writer.builder.class=gobblin.writer.SimpleDataWriterBuilder
writer.file.path.type=tablename
writer.destination.type=HDFS
writer.output.format=txt
writer.partitioner.class=gobblin.writer.partitioner.TimeBasedWriterPartitioner
writer.partition.columns=time
writer.partition.level=hourly
writer.partition.pattern=yyyyMMdd/HH
writer.partition.timezone=Asia/Shanghai
data.publisher.type=gobblin.publisher.TimePartitionedDataPublisher

#metrics
metrics.reporting.file.enabled=true
metrics.reporting.file.suffix=txt

#fs
fs.uri=hdfs://$name_node:8020
writer.fs.uri=${fs.uri}
state.store.fs.uri=${fs.uri}

data.publisher.final.dir=${env:GOBBLIN_WORK_DIR}/job-output
metrics.log.dir=${env:GOBBLIN_WORK_DIR}/metrics
state.store.dir=${env:GOBBLIN_WORK_DIR}/state-store
mr.job.root.dir=${env:GOBBLIN_WORK_DIR}/working
task.data.root.dir=${env:GOBBLIN_WORK_DIR}/task-data

修改其中的$kafka_brokers,$kafka_topics,$name_node即可；

这里的配置为standalone每小时执行一次，每次执行时根据数据中的time字段来格式化为时间分区进行存放到hdfs上的指定目录；

2 启动

export GOBBLIN_JOB_CONFIG_DIR=/opt/gobblin/gobblin-dist/job_conf
export GOBBLIN_WORK_DIR=/opt/gobblin/gobblin-dist/work_dir

bin/gobblin-standalone.sh start

3 定制化

1）希望按照当前时间（而不是数据中的时间）进行时间分区

package gobblin.writer.partitioner;

import gobblin.configuration.State;

public class DefaultTimeBasedWriterPartitioner extends TimeBasedWriterPartitioner {
    public DefaultTimeBasedWriterPartitioner(State state, int numBranches, int branchId) {
        super(state, numBranches, branchId);
    }
    public long getRecordTimestamp(Object record) {
        return System.currentTimeMillis();
    }
}

配置：

writer.partitioner.class=gobblin.writer.partitioner.DefaultTimeBasedWriterPartitioner

2）只保存json数据，并且添加换行

package gobblin.source.extractor.extract.kafka;

import gobblin.configuration.WorkUnitState;
import gobblin.source.extractor.Extractor;

import java.io.IOException;

public class JsonKafkaSimpleSource extends KafkaSimpleSource {
    public JsonKafkaSimpleSource() {}
    @Override
    public Extractor<String, byte[]> getExtractor(WorkUnitState state) throws IOException {
        return new JsonKafkaSimpleExtractor(state);
    }
}

package gobblin.source.extractor.extract.kafka;

import gobblin.configuration.WorkUnitState;
import gobblin.kafka.client.ByteArrayBasedKafkaRecord;

import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class JsonKafkaSimpleExtractor extends KafkaSimpleExtractor {
    public JsonKafkaSimpleExtractor(WorkUnitState state) {
        super(state);
    }

    @Override
    protected byte[] decodeRecord(ByteArrayBasedKafkaRecord kafkaConsumerRecord) throws IOException {
        byte[] resultBytes = kafkaConsumerRecord.getMessageBytes();
        String result = new String(resultBytes, "UTF-8");
        if (result != null && result.length() > 2 && result.charAt(0) == '{' && result.charAt(result.length() - 1) == '}')
            return (result + "\n").getBytes("UTF-8");
        else {
            System.out.println("[" + new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date()) + "]found invalid json : " + result);
            return "".getBytes();
        }
    }
}

配置：

source.class=gobblin.source.extractor.extract.kafka.JsonKafkaSimpleSource

4 docker image

https://hub.docker.com/r/gobblin/gobblin-standalone

docker run -d gobblin/gobblin-standalone:ubuntu-gobblin-0.10.0

参考：

https://gobblin.readthedocs.io/en/latest/case-studies/Kafka-HDFS-Ingestion/

https://gobblin.readthedocs.io/en/latest/user-guide/Configuration-Properties-Glossary/