Mesos笔记 （5）—— 资源

本文参考Building Applications on Mesos：

Mesos Slave提供的通用资源包含：CPUs，memory，disk和ports。需要注意的是CPUs的值定义：

Slave为不同的role预留资源有两种方式：
静态方式：在命令行指定不同的role获得不同的资源：

获取资源的函数：

namespace mesos {
namespace internal {
namespace slave {

// TODO(idownes): Move this to the Containerizer interface to complete
// the delegation of containerization, i.e., external containerizers should be
// able to report the resources they can isolate.
Try<Resources> Containerizer::resources(const Flags& flags)
{
  Try<Resources> parsed = Resources::parse(
      flags.resources.getOrElse(""), flags.default_role);

  if (parsed.isError()) {
    return Error(parsed.error());
  }

  Resources resources = parsed.get();

  // NOTE: We need to check for the "cpus" string within the flag
  // because once Resources are parsed, we cannot distinguish between
  //  (1) "cpus:0", and
  //  (2) no cpus specified.
  // We only auto-detect cpus in case (2).
  // The same logic applies for the other resources!
  if (!strings::contains(flags.resources.getOrElse(""), "cpus")) {
    // No CPU specified so probe OS or resort to DEFAULT_CPUS.
    double cpus;
    Try<long> cpus_ = os::cpus();
    if (!cpus_.isSome()) {
      LOG(WARNING) << "Failed to auto-detect the number of cpus to use: '"
                   << cpus_.error()
                   << "'; defaulting to " << DEFAULT_CPUS;
      cpus = DEFAULT_CPUS;
    } else {
      cpus = cpus_.get();
    }

    resources += Resources::parse(
        "cpus",
        stringify(cpus),
        flags.default_role).get();
  }

  // Memory resource.
  ......
}

举个例子：启动Slave时参数为--resources=gpgpus:1，则Resources::parse函数会解析gpgpus资源；由于命令行没有提供CPU，memory之类的参数，需要调用os::cpus()等方法来获得。