Platform Thread For Blocking Task
ID |
java.platform_thread_for_blocking_task |
Severity |
low |
Remediation Complexity |
trivial |
Remediation Risk |
low |
Remediation Effort |
low |
Resource |
Efficiency |
Language |
Java |
Tags |
concurrency, efficiency |
Description
Reports new Thread(task) when task’s body contains a heavy blocking operation from a configurable list — `Thread.sleep, blocking stream or socket I/O, a synchronous HTTP client send. The task is only inspected when it is written directly at the call site, as a lambda or an anonymous Runnable; a method reference or a variable holding the task is left alone. ExecutorService submissions are out of scope, since whether the backing executor uses virtual or platform threads cannot be traced back from the submission call alone.
Rationale
A platform thread that spends most of its life waiting on I/O still occupies an OS thread for the whole wait, and the OS can only host so many of those at once. A virtual thread unmounts from its carrier at the exact point it blocks, freeing that OS thread for other work, which makes it the cheaper choice for exactly this shape of task — the code is not wrong, it is just a more expensive way to run it.
new Thread(() -> {
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
throw new RuntimeException(e);
}
}).start();Remediation
Start the same task on a virtual thread instead.
Thread.ofVirtual().start(() -> {
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
throw new RuntimeException(e);
}
});