DataStax Enterprise:Spark Cassandra批量大小

Question

我在SparkConf中设置参数spark.cassandra.output.batch.size.rows,如下所示:

val conf = new SparkConf(true)
        .set("spark.cassandra.connection.host", "host")
        .set("spark.cassandra.auth.username", "cassandra")            
        .set("spark.cassandra.auth.password", "cassandra")
        .set("spark.cassandra.output.batch.size.rows", "5120")
        .set("spark.cassandra.output.concurrent.writes", "10")

但是当我表演的时候

saveToCassandra( "数据", "ten_days")

我继续在我的system.log中看到警告

NFO [FlushWriter:7] 2014-11-20 11:11:16,498 Memtable.java (line 395) Completed flushing /var/lib/cassandra/data/system/hints/system-hints-jb-76-Data.db (5747287 bytes) for commitlog position ReplayPosition(segmentId=1416480663951, position=44882909)
 INFO [FlushWriter:7] 2014-11-20 11:11:16,499 Memtable.java (line 355) Writing Memtable-ten_days@1656582530(32979978/329799780 serialized/live bytes, 551793 ops)
 WARN [Native-Transport-Requests:761] 2014-11-20 11:11:16,499 BatchStatement.java (line 226) Batch of prepared statements for [data.ten_days] is of size 36825, exceeding specified threshold of 5120 by 31705.
 WARN [Native-Transport-Requests:777] 2014-11-20 11:11:16,500 BatchStatement.java (line 226) Batch of prepared statements for [data.ten_days] is of size 36813, exceeding specified threshold of 5120 by 31693.
 WARN [Native-Transport-Requests:822] 2014-11-20 11:11:16,501 BatchStatement.java (line 226) Batch of prepared statements for [data.ten_days] is of size 36823, exceeding specified threshold of 5120 by 31703.
 WARN [Native-Transport-Requests:835] 2014-11-20 11:11:16,500 BatchStatement.java (line 226) Batch of prepared statements for [data.ten_days] is of size 36817, exceeding specified threshold of 5120 by 31697.
 WARN [Native-Transport-Requests:781] 2014-11-20 11:11:16,501 BatchStatement.java (line 226) Batch of prepared statements for [data.ten_days] is of size 36817, exceeding specified threshold of 5120 by 31697.
 WARN [Native-Transport-Requests:755] 2014-11-20 11:11:16,501 BatchStatement.java (line 226) Batch of prepared statements for [data.ten_days] is of size 36822, exceeding specified threshold of 5120 by 31702.

我知道这只是警告,但我想了解为什么我的设置没有按预期工作.然后我可以在我的集群中看到很多提示.批量大小是否会影响群集中的提示数量？

谢谢

Answer 1

您已设置批量大小行而不是批量大小字节.这意味着连接器限制行数而不是批量的内存大小.

spark.cassandra.output.batch.size.rows:每批次的行数; 默认为'auto',表示连接器将根据每行中的数据量调整行数

spark.cassandra.output.batch.size.bytes:批处理的最大总大小(以字节为单位); 默认为64 kB.

https://github.com/datastax/spark-cassandra-connector/blob/master/doc/5_saving.md

更重要的是,您可能会更好地使用更大的批处理大小(64kb)并更改cassandra.yaml文件中的警告限制.

编辑:

最近我们已经看到,较大的批次可能会导致某些C*配置不稳定,因此如果系统变得不稳定,则会降低该值.