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https://issues.apache.org/jira/browse/FLINK-10186?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16590696#comment-16590696
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ASF GitHub Bot commented on FLINK-10186:
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Guibo-Pan commented on a change in pull request #6591: [FLINK-10186] Fix
FindBugs warnings: Random object created and used o…
URL: https://github.com/apache/flink/pull/6591#discussion_r212410516
##########
File path:
flink-streaming-java/src/main/java/org/apache/flink/streaming/runtime/io/BufferSpiller.java
##########
@@ -115,7 +115,7 @@ public BufferSpiller(IOManager ioManager, int pageSize)
throws IOException {
this.tempDir = tempDirs[DIRECTORY_INDEX.getAndIncrement() %
tempDirs.length];
byte[] rndBytes = new byte[32];
- new Random().nextBytes(rndBytes);
Review comment:
It's inside constructor method, and just randoms for once in an instance.
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> FindBugs warnings: Random object created and used only once
> -----------------------------------------------------------
>
> Key: FLINK-10186
> URL: https://issues.apache.org/jira/browse/FLINK-10186
> Project: Flink
> Issue Type: Bug
> Components: Streaming
> Reporter: Hiroaki Yoshida
> Priority: Major
> Labels: pull-request-available
>
> FindBugs-3.0.1 ([http://findbugs.sourceforge.net/]) reported a
> DMI_RANDOM_USED_ONLY_ONCE warning on master:
> {code:java}
> H B DMI: Random object created and used only once in new
> org.apache.flink.streaming.runtime.io.BufferSpiller(IOManager, int) At
> BufferSpiller.java:[line 118]
> {code}
> The description of the bug is as follows:
> {quote}*DMI: Random object created and used only once
> (DMI_RANDOM_USED_ONLY_ONCE)*
> This code creates a java.util.Random object, uses it to generate one random
> number, and then discards the Random object. This produces mediocre quality
> random numbers and is inefficient. If possible, rewrite the code so that the
> Random object is created once and saved, and each time a new random number is
> required invoke a method on the existing Random object to obtain it.
> If it is important that the generated Random numbers not be guessable, you
> must not create a new Random for each random number; the values are too
> easily guessable. You should strongly consider using a
> java.security.SecureRandom instead (and avoid allocating a new SecureRandom
> for each random number needed).
> [http://findbugs.sourceforge.net/bugDescriptions.html#DMI_RANDOM_USED_ONLY_ONCE]
> {quote}
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