maxConcurrentExecutionsReached() has a race-condition where multiple instances can start before it returns a result

[ccanning]

In the launch method of LocalTaskLauncher, the

if (this.maxConcurrentExecutionsReached()) {
			throw new IllegalStateException(
				String.format("Cannot launch task %s. The maximum concurrent task executions is at its limit [%d].",
					request.getDefinition().getName(), this.getMaximumConcurrentTasks())
			);
		}

check isn't synchronized, and multiple instances can start before this code returns

public int getRunningTaskExecutionCount() {
		int runningExecutionCount = 0;

		for (TaskInstance taskInstance: running.values()) {
			if (taskInstance.getProcess().isAlive()) {
				runningExecutionCount++;
			}
		}
		return runningExecutionCount;
	}

an easy test is to set the max instances to 1 and kick off multiple concurrent requests and have it start docker tasks.

From investigation, the other launchers handle this differently and don't seem to have this issue.