[Chromoting] The daemon process now starts the networking process and passes the host configuration…

remoting/host/daemon_config_watcher.cc

+// Copyright (c) 2012 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.
+
+#include "remoting/host/daemon_config_watcher.h"
+
+#include "base/bind.h"
+#include "base/bind_helpers.h"
+#include "base/files/file_path_watcher.h"
+#include "base/file_util.h"
+#include "base/single_thread_task_runner.h"
+
+namespace remoting {
+
+// The name of the command-line switch used to specify the host configuration
+// file to use.
+const char kHostConfigSwitchName[] = "host-config";
+
+const FilePath::CharType kDefaultHostConfigFile[] =
+    FILE_PATH_LITERAL("host.json");
+
+DaemonConfigWatcher::Delegate::~Delegate() {
+}
+
+DaemonConfigWatcher::DaemonConfigWatcher(
+    scoped_refptr<base::SingleThreadTaskRunner> main_task_runner,
+    scoped_refptr<base::SingleThreadTaskRunner> io_task_runner,
+    const base::WeakPtr<Delegate>& delegate)
+    : delegate_(delegate),
+      main_task_runner_(main_task_runner),
+      io_task_runner_(io_task_runner) {
+}
+
+DaemonConfigWatcher::~DaemonConfigWatcher() {
+}
+
+void DaemonConfigWatcher::Watch(const FilePath& config_path) {
+  if (!io_task_runner_->BelongsToCurrentThread()) {
+    io_task_runner_->PostTask(FROM_HERE, base::Bind(&DaemonConfigWatcher::Watch,
+                                                 base::Unretained(this),
+                                                 config_path));
+    return;
+  }
+
+  DCHECK(config_path_.empty());
+  DCHECK(config_updated_timer_.get() == NULL);
+  DCHECK(config_watcher_.get() == NULL);
+
+  // Create the timer that will be used for delayed-reading the configuration
+  // file.
+  config_updated_timer_.reset(new base::DelayTimer<DaemonConfigWatcher>(
+      FROM_HERE, base::TimeDelta::FromSeconds(2), this,
+      &DaemonConfigWatcher::ReloadConfig));
+
+  // Start watching the configuration file.
+  config_watcher_.reset(new base::files::FilePathWatcher());
+  config_path_ = config_path;
+  if (!config_watcher_->Watch(config_path_,
+                              base::Bind(&DaemonConfigWatcher::OnConfigUpdated,
+                                         base::Unretained(this)))) {
+    LOG(ERROR) << "Couldn't watch file '" << config_path_.value() << "'";
+    main_task_runner_->PostTask(
+        FROM_HERE,
+        base::Bind(&Delegate::OnConfigWatcherError, delegate_));
+    return;
+  }
+
+  // Force reloading of the configuration file at least once.
+  ReloadConfig();
+}
+
+void DaemonConfigWatcher::Stop(scoped_ptr<DaemonConfigWatcher> self) {
+  if (!io_task_runner_->BelongsToCurrentThread()) {
+    io_task_runner_->PostTask(FROM_HERE, base::Bind(&DaemonConfigWatcher::Stop,
+                                                 base::Unretained(this),
+                                                 base::Passed(&self)));
+    return;
+  }
+
+  config_updated_timer_.reset(NULL);
+  config_watcher_.reset(NULL);
+}
+
+void DaemonConfigWatcher::OnConfigUpdated(const FilePath& path, bool error) {
+  DCHECK(io_task_runner_->BelongsToCurrentThread());
+
+  // Call ReloadConfig() after a short delay, so that we will not try to read
+  // the updated configuration file before it has been completely written.
+  // If the writer moves the new configuration file into place atomically,
+  // this delay may not be necessary.

[Wez, 2012/08/24 22:20:38]

If we fixed our config-writing code to write & rename, or fixed the
OnConfigUpdated handling to ignore incomplete configs, then we could get rid of
this hack this class would become a simple wrapper to run FilePathWatcher on the
IO thread?

[alexeypa (please no reviews), 2012/08/27 23:16:41]

More or less. I'd keep the delay regardless of the actual implementation of the
writer because this one allows us to handle both atomic and non/atomic writers
(to some extent).

+  if (!error && config_path_ == path)
+    config_updated_timer_->Reset();
+}
+
+void DaemonConfigWatcher::ReloadConfig() {
+  DCHECK(io_task_runner_->BelongsToCurrentThread());
+
+  std::string config;
+  if (!file_util::ReadFileToString(config_path_, &config)) {
+    LOG(ERROR) << "Failed to read '" << config_path_.value() << "'";
+    main_task_runner_->PostTask(
+        FROM_HERE,
+        base::Bind(&Delegate::OnConfigWatcherError, delegate_));
+    return;
+  }
+
+  main_task_runner_->PostTask(
+      FROM_HERE,
+      base::Bind(&Delegate::OnConfigUpdated, delegate_, config));
+}
+
+}  // namespace remoting