Use Chrome to transport Chrome OS metrics.

Chrome periodically reads the content of a well-know file, 
and parses it into name-value pairs, each representing a 
Chrome OS metrics event. The events are then logged using 
the normal UMA mechanism. The file is then truncated to 
zero size. Chrome uses flock() to synchronize accesses 
to the file. 
BUG=none 
TEST=compiled and run Linux and Chrome OS versions. 
Verified that uploaded Chrome OS events appear in about:histograms. 
Also external_metrics_unittest.cc tests the collection of metrics 
messages from the well-known file.

patch written by semenzato_google.com
original code review: http://codereview.chromium.org/378013
(plus http://codereview.chromium.org/346041)


Review URL: http://codereview.chromium.org/394010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@31952 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 98 insertions, 0 deletions

diff --git a/chrome/browser/chromeos/external_metrics.h b/chrome/browser/chromeos/external_metrics.h
new file mode 100644
index 0000000..2721939
--- /dev/null
+++ b/chrome/browser/chromeos/external_metrics.h
@@ -0,0 +1,98 @@
+// Copyright (c) 2009 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 CHROME_BROWSER_CHROMEOS_EXTERNAL_METRICS_H_
+#define CHROME_BROWSER_CHROMEOS_EXTERNAL_METRICS_H_
+
+#include "base/basictypes.h"
+#include "base/compiler_specific.h"
+#include "base/task.h"
+#include "testing/gtest/include/gtest/gtest_prod.h"  // For FRIEND_TEST
+
+class Profile;
+
+namespace chromeos {
+
+// ExternalMetrics is a service that Chrome offers to Chrome OS to upload
+// metrics to the UMA server on its behalf.  Chrome periodically reads the
+// content of a well-know file, and parses it into name-value pairs, each
+// representing a Chrome OS metrics event. The events are logged using the
+// normal UMA mechanism. The file is then truncated to zero size. Chrome uses
+// flock() to synchronize accesses to the file.
+class ExternalMetrics : public base::RefCountedThreadSafe<ExternalMetrics> {
+  FRIEND_TEST(ExternalMetricsTest, ParseExternalMetricsFile);
+  friend class base::RefCountedThreadSafe<ExternalMetrics>;
+
+ public:
+  ExternalMetrics() {}
+
+  // Begins the external data collection.  Profile is passed through to
+  // UserMetrics::RecordAction.  The lifetime of profile must exceed that of
+  // the external metrics object.
+  void Start(Profile* profile);
+
+ private:
+  // There is one function with this type for each action or histogram.
+  typedef void (*RecordFunctionType)(const char*);
+  // The type of event associated with each name.
+  typedef enum {
+    EVENT_TYPE_ACTION,
+    EVENT_TYPE_HISTOGRAM
+  } MetricsEventType;
+  // Used in mapping names (C strings) into event-recording functions.
+  typedef struct {
+    const char* name;
+    RecordFunctionType function;
+    MetricsEventType type;
+  } RecordFunctionTableEntry;
+  typedef void (*RecorderType)(const char*, const char*);  // See SetRecorder.
+
+  // The max length of a message (name-value pair, plus header)
+  static const int kMetricsMessageMaxLength = 4096;
+
+  ~ExternalMetrics();
+
+  // Protect action recorders from being called when external_metrics_profile is
+  // null.  This could happen when testing, or in the unlikely case that the
+  // order of object deletion at shutdown changes.
+  static void RecordActionWrapper(RecordFunctionType);
+
+  // Maps a name to an entry in the record function table.  Return NULL on
+  // failure.
+  static const ExternalMetrics::RecordFunctionTableEntry* FindRecordEntry(
+      const char* name);
+
+  // Initializes a table that maps a metric name to a function that logs that
+  // metric.
+  void InitializeFunctionTable();
+
+  // Passes an event, either an ACTION or HISTOGRAM depending on |name|, to the
+  // UMA service.  For a histogram, |value| contains the numeric value, in a
+  // format that depends on |name|.
+  static void RecordEvent(const char* name, const char* value);
+
+  // Collects external events from metrics log file.  This is run at periodic
+  // intervals.
+  void CollectEvents();
+
+  // Calls CollectEvents and reschedules a future collection.
+  void CollectEventsAndReschedule();
+
+  // Schedules a metrics event collection in the future.
+  void ScheduleCollector();
+
+  // Sets the event logging function.  Exists only because of testing.
+  void SetRecorder(RecorderType recorder) {
+    recorder_ = recorder;
+  }
+
+  // This table maps event names to event recording functions.
+  static RecordFunctionTableEntry function_table_[];
+  RecorderType recorder_;  // See SetRecorder.
+  DISALLOW_COPY_AND_ASSIGN(ExternalMetrics);
+};
+
+}  // namespace chromeos
+
+#endif  // CHROME_BROWSER_CHROMEOS_EXTERNAL_METRICS_H_