Function main

src/launcher/fetcher.cpp:533–627

This "fetcher program" is invoked by the slave's fetcher actor (Fetcher, FetcherProcess) to "fetch" URIs into the sandbox directory of a given task. Its parameters are provided in the form of the env var MESOS_FETCHER_INFO which contains a FetcherInfo (see fetcher.proto) object formatted in JSON. These are set by the actor to indicate what set of URIs to process and how to proceed with each one. A

// have multiple instances of this fetcher program running at any
// given time. Exit code: 0 if entirely successful, otherwise 1.
int main(int argc, char* argv[])
{
  GOOGLE_PROTOBUF_VERIFY_VERSION;

  mesos::internal::logging::Flags flags;

  Try<flags::Warnings> load = flags.load("MESOS_", argc, argv);

  if (flags.help) {
    std::cout << flags.usage() << std::endl;
    return EXIT_SUCCESS;
  }

  if (load.isError()) {
    std::cerr << flags.usage(load.error()) << std::endl;
    return EXIT_FAILURE;
  }

  logging::initialize(argv[0], true, flags); // Catch signals.

  // Log any flag warnings (after logging is initialized).
  foreach (const flags::Warning& warning, load->warnings) {
    LOG(WARNING) << warning.message;
  }

  const Option<string> jsonFetcherInfo = os::getenv("MESOS_FETCHER_INFO");
  CHECK_SOME(jsonFetcherInfo)
    << "Missing MESOS_FETCHER_INFO environment variable";

  LOG(INFO) << "Fetcher Info: " << jsonFetcherInfo.get();

  Try<JSON::Object> parse = JSON::parse<JSON::Object>(jsonFetcherInfo.get());
  CHECK_SOME(parse) << "Failed to parse MESOS_FETCHER_INFO: " << parse.error();

  Try<FetcherInfo> fetcherInfo = ::protobuf::parse<FetcherInfo>(parse.get());
  CHECK_SOME(fetcherInfo)
    << "Failed to parse FetcherInfo: " << fetcherInfo.error();

  CHECK(!fetcherInfo->sandbox_directory().empty())
    << "Missing sandbox directory";

  const string sandboxDirectory = fetcherInfo->sandbox_directory();

  Try<Nothing> result = createCacheDirectory(fetcherInfo.get());
  if (result.isError()) {
    EXIT(EXIT_FAILURE)
      << "Could not create the fetcher cache directory: " << result.error();
  }

  // If the `FetcherInfo` specifies a user, use `os::su()` to fetch files as the
  // task's user to ensure that filesystem permissions are enforced.
  if (fetcherInfo->has_user()) {
  // TODO(coffler): No support for os::su on Windows, see MESOS-8063
#ifndef __WINDOWS__
    result = os::su(fetcherInfo->user());
    if (result.isError()) {
      EXIT(EXIT_FAILURE) << "Fetcher could not execute `os::su()` for user '"
                         << fetcherInfo->user() << "'";