How to obtain unique JVM identifier?

Question

How can Java code obtain a unique identifier for the JVM in which it's running? On a Unix system, an example of what I'm looking for would be the PID of the process in which the JVM is running (assuming a one-to-one mapping between JVM's and processes).

See http://stackoverflow.com/questions/35842/process-id-in-java for more info on getting process ID from the current Java process. [This blog entry](http://blog.igorminar.com/2007/03/how-java-application-can-discover-its.html) also has some good info. — prunge, Nov 28 '11 at 22:03

score 15 · Answer 1 · answered Sep 19 '17 at 14:49

15

We have been using:

import java.lang.management.ManagementFactory;
String jvmName = ManagementFactory.getRuntimeMXBean().getName();

Which gives something like <pid>@<hostname>, at least in Sun/Oracle JVMs.

answered Sep 19 '17 at 14:49

Erik van Oosten

1,541
14
16

Running on docker it will always return something like "1@localhost" – deFreitas Jun 01 '23 at 15:52
So we we need a new mechanism... – Erik van Oosten Jun 02 '23 at 17:15
I ended by creating singleton instance variable with random UUID – deFreitas Jun 05 '23 at 22:10

score 13 · Answer 2 · answered Nov 28 '11 at 21:38

One simple method of creating a unique ID for each JVM is to start a static ServerSocket, set to use port 0 upon which it will grab any free port. Since no two ServerSockets (JVM or otherwise) can exist on the same port they will all be unique and you can query it for the port number. Since it is static there will be only one per JVM.

This does depend on what permissions you have but in most cases it works just fine and you can always have it bind to "127.0.0.1" to make it less likely to come up against any restrictions.

static ServerSocket myssock;
static int myid;

static {
    myssock = new ServerSocket(0);
    myid = myssock.getLocalPort();
}

If you have multiple JVMs across multiple host machines then you can combine the above with the machine's LAN IP to create a unique JVM ID across a network.

score 0 · Answer 3 · answered May 06 '20 at 05:38

Basically this all falls on its ass when you consider that you might have JVMs spread across multiple hosts, LANs, or could be used in docker containers you're basically down to generate a UUID from /dev/random.

If having duplicates could cost serious $$$, you might want to avoid this. However if you'd like to know how likely this is consider the math behind the birthday paradox. Since a random UUID has a key space of 2^122, and supposing you have a million JVMs, the probability of a collision is approximately 1e-22

How to obtain unique JVM identifier?

3 Answers3

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