hehuiyuan opened a new pull request #23997: Branch 2.4
URL: https://github.com/apache/spark/pull/23997
 
 
   ## What changes were proposed in this pull request?
   
   In streaming-programming-guide.md, as follows:
   
   *Setting the max receiving rate* - If the cluster resources is not large 
enough for the streaming
     application to process data as fast as it is being received, the receivers 
can be rate limited
     by setting a maximum rate limit in terms of records / sec.
     See the [configuration parameters](configuration.html#spark-streaming)
     `spark.streaming.receiver.maxRate` for receivers and 
`spark.streaming.kafka.maxRatePerPartition`
     for Direct Kafka approach. In Spark 1.5, we have introduced a feature 
called *backpressure* that
     eliminate the need to set this rate limit, as Spark Streaming 
automatically figures out the
     rate limits and dynamically adjusts them if the processing conditions 
change. This backpressure
     can be enabled by setting the [configuration 
parameter](configuration.html#spark-streaming)
     `spark.streaming.backpressure.enabled` to `true`.
   
   I think we should be more rigorous. The first batch may be processing all 
the time and can not run normally when the first batch of data is very large 
for Direct Kafka approach .
   
   Add additional explanation:
   
   In Spark 1.5, we have introduced a feature called *backpressure* that
     eliminate the need to set this rate limit, as Spark Streaming 
automatically figures out the
     rate limits and dynamically adjusts them if the processing conditions 
change.Setting this rate limit when  the first batch of data is very large 
which causes the task not to work properly,
   
   
   

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