leventov commented on a change in pull request #6662: Double-checked locking
bug is fixed.
URL: https://github.com/apache/incubator-druid/pull/6662#discussion_r236302382
##########
File path:
aws-common/src/main/java/org/apache/druid/common/aws/LazyFileSessionCredentialsProvider.java
##########
@@ -32,14 +32,10 @@ public
LazyFileSessionCredentialsProvider(AWSCredentialsConfig config)
this.config = config;
}
- private FileSessionCredentialsProvider getUnderlyingProvider()
+ private synchronized FileSessionCredentialsProvider getUnderlyingProvider()
Review comment:
The former code here is indeed buggy, however putting `synchronized` on
`getUnderlyingProvider()` is not how this method should be fixed.
Please make the following:
1. Declare `config` field `final`
2. Add a comment noting that `FileSessionCredentialsProvider` is safely
initialized because it contains a `final` field `sessionCredentials`. Also a
comment should be added on that field noting that `final` modifier should not
be removed from it, because it has concurrency implications in
`LazyFileSessionCredentialsProvider`.
3. In `getUnderlyingProvider()`, `provider` should be read into a local
variable, local variable updated in the `synchronized` block along with the
field, and the local is returned in the last line of the method. This is
because currently the second read of `provider` in the last line of the method
could return `null` even if the first read in the first line returned non-null
and the `synchronized` block was not entered.
----------------------------------------------------------------
This is an automated message from the Apache Git Service.
To respond to the message, please log on GitHub and use the
URL above to go to the specific comment.
For queries about this service, please contact Infrastructure at:
[email protected]
With regards,
Apache Git Services
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
