If your application is running in Linux, then you consider installing the ‘haveged’ library. If you are running on the older version of RHEL, you can follow the recommendations given here to fix this problem.
#JAVA UUID GENERATOR UPGRADE#
If you can upgrade to RHEL 7 or above version, please do so. This problem has been resolved in RHEL 7 and above versions. If this problem surfaces in your application, the following are the potential solutions to address them: 1. It may lead to BLOCKED threads in the applications. If you see the value to be less than 1000, then it indicates there is a lack of entropy. To check the availability of entropy in Linux execute the below command: cat /proc/sys/kernel/random/entropy_avail Thus it was making the application unresponsive. You can notice that the thread got into a BLOCKED state when invoking ‘#randomUUID()’ due to a lack of ‘entropy’ and unable to progress forward. (ExecuteThread.java:221)įig: Stack trace of a thread stuck while making ‘#randomUUID()’ API call securedExecute(WebAppServletContext.java:2273) AuthenticatedSubject.doAs(AuthenticatedSubject.java:321) $ServletInvocationAction.wrapRun(WebAppServletContext.java:3730) (SecureRandom.java:433)Ĭom.topComponentMethodBbuggycompanyin(RootTracer.java:439) Below is the stack trace of one of that 50 threads: " ExecuteThread: '1' for queue: ' (self-tuning)'" waiting for lock In these 102 threads 50 threads are in the BLOCKED state due to ‘#randomUUID()’ API call. In the thread dump report, you can notice that there are 102 threads in total. (Note: in the thread dump report, we have changed the package name to ‘buggycompany’ to hide the identity of the application). It would give the better context of the problem. If you haven’t clicked on the hyperlink in the previous sentence, we request you do so. Here is a real-world thread dump report of an application that was suffering from this problem. Real world application – 50 threads BLOCKED in #randomUUID() API
#JAVA UUID GENERATOR CODE#
If your application uses ‘#randomUUID()’ API in a critical code path and there is a lack of entropy in the operating system, then multiple threads can enter into this BLOCKED state bringing your entire application to a grinding halt. When there is a slowdown, application threads which are calling this ‘#randomUUID()’ API call will be put in a BLOCKED state, and they wouldn’t be able to progress further. When there is a lack of ‘entropy’ in the operating system then random number generation will slow down.
#JAVA UUID GENERATOR DRIVERS#
What does ‘entropy’ mean? Linux kernel uses certain techniques like user’s mouse movements, variance in the hardware fan noise, variance in the noise of the device drivers … to generate random numbers. #randomUUID() API internally uses ‘ entropy‘ in the operating system to generate a unique number. Let’s discuss this API in this post with a real-world example.
Under certain circumstances, using this API can affect your application’s availability. Java developers tend to use ‘#randomUUID()’ API, to generate a UUID (Universally Unique Identifier) number (i.e., ‘b8bbcbed-ca07-490c-8711-5118ee0af2f9’). 1.7K Training / Learning / Certification.165.3K Java EE (Java Enterprise Edition).
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