Reporting of policy errors via host-offline-reason: part 3

remoting/host/minimum_heartbeat_supporter.h

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef REMOTING_HOST_MINIMUM_HEARTBEAT_SUPPORTER_H_
+#define REMOTING_HOST_MINIMUM_HEARTBEAT_SUPPORTER_H_
+
+#include <string>
+
+#include "base/callback.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/time/time.h"

[Lambros, 2014/12/05 22:19:48]

Don't need time.h ?

[Łukasz Anforowicz, 2014/12/05 23:59:28]

Done.

+#include "remoting/base/auto_thread_task_runner.h"
+#include "remoting/base/rsa_key_pair.h"
+#include "remoting/host/ack_or_timeout_reporter.h"
+#include "remoting/signaling/xmpp_signal_strategy.h"
+
+namespace base {
+class TimeDelta;
+}
+
+namespace net {
+class NetworkChangeNotifier;
+}
+
+namespace remoting {
+
+class ChromotingHostContext;
+class DnsBlackholeChecker;
+class HeartbeatSender;
+class OAuthTokenGetter;
+class SignalStrategy;
+class SignalingConnector;
+
+// Keeping an instance of MinimumHeartbeatSupporter alive
+// ensures that we keep trying to send heartbeats (which among other

[Lambros, 2014/12/05 22:19:48]

"among other things"?
Remove this, or say what those things actually are.

This whole phrasing is not very clear to me. It seems to me this class has two
functions:
1) Keep sending regular heartbeats to the host.
2) Keep the host process alive during shutdown, until the reason-code for
shutdown has been sent and acknowledged (subject to timeout).
Am I right?

[Łukasz Anforowicz, 2014/12/05 23:59:28]

The comment was not trying to explain the purpose of *the class*, but rather
trying to explain what is accomplished by keeping an instance of the class
alive.  I'll reword the comment as suggested.

+// things means that it ensures that we don't exit the host process).
+//
+// Primary scenario where this class is useful is extending host process
+// lifetime after |SendHostOfflineReason| is called.
+//
+// Secondary benefit of this class is hiding/encapsulating heartbeat
+// and xmpp related things inside.
+class MinimumHeartbeatSupporter
+    : public base::RefCounted<MinimumHeartbeatSupporter> {
+ public:
+  // TODO(lukasza): Refactor to limit the number of parameters below.
+  // Probably necessitates refactoring HostProcess to extract a new
+  // class to read and store config/policy/cmdline values.
+  static scoped_refptr<MinimumHeartbeatSupporter> Create(
+      const base::Closure& on_heartbeat_successful_callback,
+      const base::Closure& on_unknown_host_id_error_callback,
+      const base::Closure& on_auth_failed_callback,
+      const ChromotingHostContext& host_context,
+      const XmppSignalStrategy::XmppServerConfig& xmpp_server_config,
+      const std::string& talkgadget_prefix,
+      const std::string& host_id,
+      const scoped_refptr<const RsaKeyPair>& key_pair,
+      const std::string& directory_bot_jid,
+      const std::string& oauth_refresh_token,
+      bool use_service_account);
+
+  // Gets signal strategy used for talking to the Chromoting bot.
+  // Return value is valid until |this| gets deleted.
+  SignalStrategy* signal_strategy() { return signal_strategy_.get(); }
+
+  // Kicks off sending a heartbeat containing a host-offline-reason attribute.
+  //
+  // Ensures that |this| (and transitively the whole process) is kept alive
+  // while waiting for an ack from the bot (this is subject to |timeout|).
+  void SendHostOfflineReason(const std::string& host_offline_reason,
+                             const base::TimeDelta& timeout);
+
+ private:
+  // Ref-counting helpers.
+  friend class base::RefCounted<MinimumHeartbeatSupporter>;
+  ~MinimumHeartbeatSupporter();
+
+  MinimumHeartbeatSupporter(
+      scoped_refptr<AutoThreadTaskRunner> network_task_runner,
+      scoped_ptr<net::NetworkChangeNotifier> network_change_notifier,
+      scoped_ptr<XmppSignalStrategy> signal_strategy,
+      scoped_ptr<SignalingConnector> signaling_connector,
+      scoped_ptr<HeartbeatSender> heartbeat_sender);
+
+  void OnAckOrTimeout(AckOrTimeout ack_or_timeout);
+
+  // Order fields below is important for destructing them in the right oder.

[Lambros, 2014/12/05 22:19:48]

nit: Order of the fields ...

[Łukasz Anforowicz, 2014/12/05 23:59:28]

Done.

+  // - |heartbeat_sender_| and |signaling_connector_| have to be destructed
+  //   before |signal_strategy_| because their destructors need to call
+  //   signal_strategy_->RemoveListener(this)
+  // - |signaling_connector_| has to be destructed before
+  //   |network_change_notifier_| because its destructor needs to deregister
+  //   network change notifications
+  // - |network_task_runner_| is used by all the other fields and has to be

[Lambros, 2014/12/05 22:19:48]

|network_task_runner_| is ref-counted, so it doesn't matter where it goes?

[Łukasz Anforowicz, 2014/12/05 23:59:28]

The other objects don't hold a reference to network_task_runner_,
but rather go through TLS storage to get a generic TaskRunner.  For example
SignalingConnector goes through base::Timer which then does the following:

https://code.google.com/p/chromium/codesearch#chromium/src/base/timer/timer.c...
:

scoped_refptr<SingleThreadTaskRunner> Timer::GetTaskRunner() {
  return task_runner_.get() ? task_runner_ : ThreadTaskRunnerHandle::Get();
}

which ends up here:

https://code.google.com/p/chromium/codesearch#chromium/src/base/thread_task_r...
:

scoped_refptr<SingleThreadTaskRunner> ThreadTaskRunnerHandle::Get() {
  ThreadTaskRunnerHandle* current = lazy_tls_ptr.Pointer()->Get();
  DCHECK(current);
  return current->task_runner_;
}

[Lambros, 2014/12/06 01:25:05]

Hmm, that doesn't feel right, but I can see why you'd want to destroy
(dereference) the AutoThreadTaskRunner last.

+  //   destructed last.
+  scoped_refptr<AutoThreadTaskRunner> network_task_runner_;
+  scoped_ptr<net::NetworkChangeNotifier> network_change_notifier_;
+  scoped_ptr<XmppSignalStrategy> signal_strategy_;
+  scoped_ptr<SignalingConnector> signaling_connector_;
+  scoped_ptr<HeartbeatSender> heartbeat_sender_;
+
+  DISALLOW_COPY_AND_ASSIGN(MinimumHeartbeatSupporter);
+};
+
+}  // namespace remoting
+
+#endif  // REMOTING_HOST_MINIMUM_HEARTBEAT_SUPPORTER_H_