Add Java process information to UUIDs.makeNode() hash
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Alex Dutra February 16, 2016 at 6:14 PM
@Peter thank you for your initial patch. There has been indeed some discussion about how to properly obtain the PID.
First of all, as @Olivier Michallat pointed out in your initial pull request, Sigar is too heavyweight for the Java driver and its binaries do not seem to be up-to-date in Maven Central.
Secondly, thanks to JAVA-727, the driver can now use JNR when available.
So my suggestion here is to try the following methods one by one, in the order they are listed below:
If the System property com.datastax.driver.PID is set then the value to use as a PID will be read from that property;
Otherwise, if a native call to getpid() is possible, then the PID will be read from that call;
Otherwise, an attempt will be made to read the PID from JMX's RuntimeMXBean name, which is a well-known, yet undocumented "hack";
If all of the above methods fail, a random integer will be generated and used as a surrogate PID.
Peter February 15, 2016 at 1:35 PM
Good to see this issue is now in progress. Please note that there has been some discussion about the patch supplied to this ticket: https://github.com/datastax/java-driver/pull/521
Peter November 12, 2015 at 10:29 AM
Same Issue within Cassandra Server is now planned for C* v2.2 https://issues.apache.org/jira/browse/CASSANDRA-7925
Alex Popescu October 8, 2015 at 1:54 AM
@Bulat Shakirzyanov @Adam Holmberg @Michael Penick @Jorge Bay Gondra can you guys double check in the other drivers? thanks
Currently there is a chance of collision if multiple Java processes on the same machine are using DataStax Java Driver to generate UUIDs. This is because the hash in
UUIDs.makeNode()(https://github.com/datastax/java-driver/blob/2.1/driver-core/src/main/java/com/datastax/driver/core/utils/UUIDs.java#L88) doesn't include any process information, such as PID. A simple fix would be to append the value ofManagementFactory.getRuntimeMXBean().getName()to the hash too.Resolution:
The driver now tries various methods to include the PID in the hash, look at the javadocs of UUIDs for the detailed description.