[Feature] Show offset lag for routine load job

[morningman]

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Description

Show the lag of each kafka offset in show routine load stmt's result.
So that we can easily monitor the status of routine load job

Use case

mysql> show routine load\G
*************************** 1. row ***************************
                  Id: 10013
                Name: test4
          CreateTime: 2021-11-13 18:59:01
           PauseTime: NULL
             EndTime: NULL
              DbName: default_cluster:db1
           TableName: tbl1
               State: RUNNING
      DataSourceType: KAFKA
      CurrentTaskNum: 1
       JobProperties: {"timezone":"Asia/Shanghai","send_batch_parallelism":"1","columnSeparator":"','","lineDelimiter":"\n","maxBatchSizeBytes":"209715200","exec_mem_limit":"2147483648","strict_mode":"false","jsonpaths":"","currentTaskConcurrentNum":"1","fuzzy_parse":"false","partitions":"*","columnToColumnExpr":"k1,k2","maxBatchIntervalS":"20","whereExpr":"*","precedingFilter":"*","mergeType":"APPEND","format":"csv","json_root":"","deleteCondition":"*","desireTaskConcurrentNum":"3","maxErrorNum":"0","strip_outer_array":"false","execMemLimit":"2147483648","num_as_string":"false","maxBatchRows":"300000"}
DataSourceProperties: {"topic":"test","currentKafkaPartitions":"0","brokerList":"xxxxx:9093"}
    CustomProperties: {"kafka_default_offsets":"OFFSET_BEGINNING","group.id":"test4"}
           Statistic: {"receivedBytes":9,"runningTxns":[],"errorRows":0,"committedTaskNum":1,"loadedRows":3,"loadRowsRate":0,"abortedTaskNum":0,"errorRowsAfterResumed":0,"totalRows":3,"unselectedRows":0,"receivedBytesRate":0,"taskExecuteTimeMs":20058}
            Progress: {"0":"2"}
                 Lag: {"0":1}
ReasonOfStateChanged:
        ErrorLogUrls:
            OtherMsg:
1 row in set (0.02 sec)

the Lag: {"0":1} shows there is 1 offset behind the latest offset of partition 0.

Related issues

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Are you willing to submit PR?

• Yes I am willing to submit a PR!

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