Method checkAndTransitionDrainingAgent

src/master/master.cpp:5502–5581

void Master::checkAndTransitionDrainingAgent(Slave* slave)
{
  CHECK_NOTNULL(slave);

  const SlaveID& slaveId = slave->id;

  if (!slaves.draining.contains(slaveId) ||
      slaves.draining.at(slaveId).state() == DRAINED) {
    // Nothing to do for non-draining or already drained agents.
    return;
  }

  // Check if the agent has any tasks running or operations pending.
  if (!slave->tasks.empty() ||
      !slave->operations.empty()) {
    size_t numTasks = 0u;
    foreachvalue (const auto& frameworkTasks, slave->tasks) {
      numTasks += frameworkTasks.size();
    }

    VLOG(1)
      << "DRAINING Agent " << slaveId << " has "
      << numTasks << " tasks, and "
      << slave->operations.size() << " operations";
    return;
  }

  if (slaves.markingGone.contains(slaveId)) {
    LOG(INFO)
      << "Ignoring transition of agent " << slaveId << " to the DRAINED"
      << " state because agent is being marked gone";
    return;
  }

  // If the agent will be marked gone afterwards, we do not need to mark
  // the agent as DRAINED. Simply marking gone will suffice.
  if (slaves.draining.at(slaveId).config().mark_gone()) {
    LOG(INFO) << "Marking agent " << slaveId << " in the DRAINED state as gone";

    slaves.markingGone.insert(slaveId);

    TimeInfo goneTime = protobuf::getCurrentTime();

    registrar->apply(Owned<RegistryOperation>(
        new MarkSlaveGone(slaveId, goneTime)))
      .onAny(defer(
          self(),
          [this, slaveId, goneTime](const Future<bool>& result) {
            CHECK_READY(result)
              << "Failed to mark agent gone in the registry";

            markGone(slaveId, goneTime);
          }));
  } else {
    LOG(INFO) << "Transitioning agent " << slaveId << " to the DRAINED state";

    registrar->apply(Owned<RegistryOperation>(
        new MarkAgentDrained(slaveId)))