Syinchwun Leo created FLINK-5756:
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Summary: When there are many values under the same key in
ListState, RocksDBStateBackend performances poor
Key: FLINK-5756
URL: https://issues.apache.org/jira/browse/FLINK-5756
Project: Flink
Issue Type: Improvement
Components: State Backends, Checkpointing
Affects Versions: 1.2.0
Environment: CentOS 7.2
Reporter: Syinchwun Leo
When using RocksDB as the StateBackend, if there are many values under the same
key in ListState, the windowState.get() operator performances very poor. I also
the the RocksDB using version 4.11.2, the performance is also very poor. The
problem is likely to related to RocksDB itself's get() operator after using
merge(). The problem may influences the window operation's performance when the
size is very large using ListState. I try to merge 50000 values under the same
key in RocksDB, It costs 120 seconds
///////////////////////////////////////////////////////////////////////////////
The flink's code is as follows:
class SEventSource extends RichSourceFunction [SEvent] {
private var count = 0L
private val alphabet =
"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWZYX0987654321"
override def run(sourceContext: SourceContext[SEvent]): Unit = {
while (true) {
for (i <- 0 until 5000) {
sourceContext.collect(SEvent(1, "hello-"+count, alphabet,1))
count += 1L
}
Thread.sleep(1000)
}
}
}
env.addSource(new SEventSource)
.assignTimestampsAndWatermarks(new AssignerWithPeriodicWatermarks[SEvent]
{
override def getCurrentWatermark: Watermark = {
new Watermark(System.currentTimeMillis())
}
override def extractTimestamp(t: SEvent, l: Long): Long = {
System.currentTimeMillis()
}
})
.keyBy(0)
.window(SlidingEventTimeWindows.of(Time.seconds(20), Time.seconds(2)))
.apply(new WindowStatistic)
.map(x => (System.currentTimeMillis(), x))
.print()
////////////////////////////////////
The RocksDB Test code:
val stringAppendOperator = new StringAppendOperator
val options = new Options()
options.setCompactionStyle(CompactionStyle.LEVEL)
.setCompressionType(CompressionType.SNAPPY_COMPRESSION)
.setLevelCompactionDynamicLevelBytes(true)
.setIncreaseParallelism(4)
.setUseFsync(true)
.setMaxOpenFiles(-1)
.setCreateIfMissing(true)
.setMergeOperator(stringAppendOperator)
val write_options = new WriteOptions
write_options.setSync(false)
val rocksDB = RocksDB.open(options, "/******/Data/")
val key = "key"
val value =
"abcdefghijklmnopqrstuvwxyz0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ7890654321"
val beginmerge = System.currentTimeMillis()
for(i <- 0 to 50000) {
rocksDB.merge(key.getBytes(), ("s"+ i + value).getBytes())
//rocksDB.put(key.getBytes, value.getBytes)
}
println("finish")
val begin = System.currentTimeMillis()
rocksDB.get(key.getBytes)
val end = System.currentTimeMillis()
println("merge cost:" + (begin - beginmerge))
println("Time consuming:" + (end - begin))
}
}
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