flink源码分析-获取最大可以打开的文件句柄

flink版本: flink-1.11.2

代码位置: org.apache.flink.runtime.util.EnvironmentInformation

调用位置:   taskmanager启动类:  

org.apache.flink.runtime.taskexecutor.TaskManagerRunner

long maxOpenFileHandles = EnvironmentInformation.getOpenFileHandlesLimit();

注意，该方法主要调用了com.sun.management.UnixOperatingSystemMXBean接口下的getMaxFileDescriptorCount方法，所以一定要在Sun/Oracle的JDK下才能使用。另外只能在基于Unix内核的操作系统中生效，其他系统下默认返回-1.

	/**
	 * Tries to retrieve the maximum number of open file handles. This method will only work on
	 * UNIX-based operating systems with Sun/Oracle Java versions.
	 *
	 * 
If the number of max open file handles cannot be determined, this method returns {@code -1}.
	 *
	 * @return The limit of open file handles, or {@code -1}, if the limit could not be determined.
	 */
	public static long getOpenFileHandlesLimit() {
		if(OperatingSystem.isWindows()) { // getMaxFileDescriptorCount method is not available on Windows
			return -1L;
		}
		Class sunBeanClass;
		try {
			sunBeanClass = Class.forName("com.sun.management.UnixOperatingSystemMXBean");
		} catch(ClassNotFoundException e) {
			return -1L;
		}

		try {
			Method fhLimitMethod = sunBeanClass.getMethod("getMaxFileDescriptorCount");
			Object result = fhLimitMethod.invoke(ManagementFactory.getOperatingSystemMXBean());
			return (Long) result;
		} catch(Throwable t) {
			LOG.warn("Unexpected error when accessing file handle limit", t);
			return -1L;
		}
	}