HeartSaVioR commented on a change in pull request #25552: [SPARK-28849][CORE]
Add a number to control transferTo calls to avoid infinite loop in some
occasional cases
URL: https://github.com/apache/spark/pull/25552#discussion_r316952694
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File path: core/src/main/scala/org/apache/spark/util/Utils.scala
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@@ -417,16 +418,19 @@ private[spark] object Utils extends Logging {
input: FileChannel,
output: WritableByteChannel,
startPosition: Long,
- bytesToCopy: Long): Unit = {
+ bytesToCopy: Long,
+ numTransferToCalls: Int): Unit = {
val outputInitialState = output match {
case outputFileChannel: FileChannel =>
Some((outputFileChannel.position(), outputFileChannel))
case _ => None
}
var count = 0L
+ var num = 0
// In case transferTo method transferred less data than we have required.
- while (count < bytesToCopy) {
+ while (count < bytesToCopy && num < numTransferToCalls) {
count += input.transferTo(count + startPosition, bytesToCopy - count,
output)
Review comment:
numTransferToCalls would depend on the size of bytesToCopy so harder to set
which value makes sense to find the issue and do fail fast. Though `transferTo`
can return 0 according to javadoc, if it would return 0 continuously (like 100
times) it sounds an issue to me.
We can also apply exponential wait here when the return value is 0, if it
turns out calling transferTo right again doesn't help. May helps to avoid
system usage going mad.
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