[iOS] Add BreadcrumbManager

Add BreadcrumbManager to locally store and discard breadcrumb events.

Bug: 1003922
Change-Id: I20ac153f22b5350129107f5efd0ac622edb07a62
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1804803
Commit-Queue: Mike Dougherty <michaeldo@chromium.org>
Reviewed-by: Eugene But <eugenebut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#706685}

ios/chrome/browser/crash_report/breadcrumbs/BUILD.gn

@@ -2,6 +2,8 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import("//ios/build/config.gni")
+
 source_set("feature_flags") {
   configs += [ "//build/config/compiler:enable_arc" ]
   sources = [
@@ -12,3 +14,31 @@ source_set("feature_flags") {
     "//base",
   ]
 }
+
+source_set("breadcrumbs") {
+  deps = [
+    "//base",
+  ]
+
+  sources = [
+    "breadcrumb_manager.cc",
+    "breadcrumb_manager.h",
+  ]
+
+  configs += [ "//build/config/compiler:enable_arc" ]
+}
+
+source_set("unit_tests") {
+  configs += [ "//build/config/compiler:enable_arc" ]
+  testonly = true
+  deps = [
+    ":breadcrumbs",
+    "//base",
+    "//base/test:test_support",
+    "//testing/gtest",
+  ]
+
+  sources = [
+    "breadcrumb_manager_unittest.mm",
+  ]
+}

ios/chrome/browser/crash_report/breadcrumbs/OWNERS

+eugenebut@chromium.org
+michaeldo@chromium.org
+
+# TEAM: ios-directory-owners@chromium.org
+# OS: iOS

ios/chrome/browser/crash_report/breadcrumbs/breadcrumb_manager.cc

+// Copyright 2019 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 "ios/chrome/browser/crash_report/breadcrumbs/breadcrumb_manager.h"
+
+#include "base/strings/stringprintf.h"
+#include "base/time/time_to_iso8601.h"
+
+namespace {
+
+// The minimum number of event buckets to keep, even if they are expired.
+const int kMinEventsBuckets = 2;
+
+// Returns a Time used to bucket events for easier discarding of expired events.
+base::Time EventBucket(const base::Time& time) {
+  base::Time::Exploded exploded;
+  time.LocalExplode(&exploded);
+  exploded.millisecond = 0;
+  exploded.second = 0;
+
+  base::Time bucket_time;
+  bool converted = base::Time::FromLocalExploded(exploded, &bucket_time);
+  DCHECK(converted);
+  return bucket_time;
+}
+
+}  // namespace
+
+std::list<std::string> BreadcrumbManager::GetEvents(size_t event_count_limit) {
+  DropOldEvents();
+
+  std::list<std::string> events;
+  for (auto it = event_buckets_.rbegin(); it != event_buckets_.rend(); ++it) {
+    std::list<std::string> bucket_events = it->second;
+    for (auto event_it = bucket_events.rbegin();
+         event_it != bucket_events.rend(); ++event_it) {
+      std::string event = *event_it;
+      events.push_front(event);
+      if (event_count_limit > 0 && events.size() >= event_count_limit) {
+        return events;
+      }
+    }
+  }
+  return events;
+}
+
+void BreadcrumbManager::AddEvent(const std::string& event) {
+  base::Time time = base::Time::Now();
+  base::Time bucket_time = EventBucket(time);
+
+  // If bucket exists, it will be at the end of the list.
+  if (event_buckets_.empty() || event_buckets_.back().first != bucket_time) {
+    std::pair<base::Time, std::list<std::string>> bucket(
+        bucket_time, std::list<std::string>());
+    event_buckets_.push_back(bucket);
+  }
+
+  std::string timestamp = base::TimeToISO8601(time);
+  std::string event_log =
+      base::StringPrintf("%s %s", timestamp.c_str(), event.c_str());
+  event_buckets_.back().second.push_back(event_log);
+
+  DropOldEvents();
+}
+
+void BreadcrumbManager::DropOldEvents() {
+  static const base::TimeDelta kMessageExpirationTime =
+      base::TimeDelta::FromMinutes(20);
+
+  base::Time now = base::Time::Now();
+  while (event_buckets_.size() > kMinEventsBuckets) {
+    base::Time oldest_bucket_time = event_buckets_.front().first;
+    if (now - oldest_bucket_time < kMessageExpirationTime) {
+      break;
+    }
+    event_buckets_.pop_front();
+  }
+}
+
+BreadcrumbManager::BreadcrumbManager() = default;
+
+BreadcrumbManager::~BreadcrumbManager() = default;

ios/chrome/browser/crash_report/breadcrumbs/breadcrumb_manager.h

+// Copyright 2019 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 IOS_CHROME_BROWSER_CRASH_REPORT_BREADCRUMBS_BREADCRUMB_MANAGER_H_
+#define IOS_CHROME_BROWSER_CRASH_REPORT_BREADCRUMBS_BREADCRUMB_MANAGER_H_
+
+#include <list>
+#include <map>
+#include <string>
+
+#import "base/time/time.h"
+
+// Stores events logged with |AddEvent| in memory which can later be retrieved
+// with |GetEvents|. Events will be silently dropped after a certain amount of
+// time has passed unless no more recent events are available. The internal
+// management of events aims to keep relevant events available while clearing
+// stale data.
+class BreadcrumbManager {
+ public:
+  // Returns a list of the collected breadcrumb events which are still relevant
+  // up to |event_count_limit|. Passing zero for |event_count_limit| signifies
+  // no limit. Events returned will have a timestamp prepended to the original
+  // |event| string representing when |AddEvent| was called.
+  std::list<std::string> GetEvents(size_t event_count_limit);
+
+  // Logs a breadcrumb event with message data |event|.
+  void AddEvent(const std::string& event);
+
+  BreadcrumbManager();
+  virtual ~BreadcrumbManager();
+
+ private:
+  // Drops events which are considered stale. Note that stale events are not
+  // guaranteed to be removed. Explicitly, stale events will be retained while
+  // newer events are limited.
+  void DropOldEvents();
+
+  // List of events, paired with the time which they were logged to minute
+  // resolution. Newer events are at the end of the list.
+  std::list<std::pair<base::Time, std::list<std::string>>> event_buckets_;
+
+  DISALLOW_COPY_AND_ASSIGN(BreadcrumbManager);
+};
+
+#endif  // IOS_CHROME_BROWSER_CRASH_REPORT_BREADCRUMBS_BREADCRUMB_MANAGER_H_

ios/chrome/browser/crash_report/breadcrumbs/breadcrumb_manager_unittest.mm

+// Copyright 2019 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 "ios/chrome/browser/crash_report/breadcrumbs/breadcrumb_manager.h"
+
+#include "base/test/task_environment.h"
+#include "base/time/time.h"
+#include "testing/gtest/include/gtest/gtest.h"
+#include "testing/gtest_mac.h"
+#include "testing/platform_test.h"
+
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
+// Test fixture for testing BreadcrumbManager class.
+class BreadcrumbManagerTest : public PlatformTest {
+ protected:
+  BreadcrumbManagerTest() {}
+
+  base::test::TaskEnvironment task_env_{
+      base::test::TaskEnvironment::TimeSource::MOCK_TIME};
+  BreadcrumbManager breadcrumb_manager_;
+};
+
+// Tests that an event is logged and returned.
+TEST_F(BreadcrumbManagerTest, AddEvent) {
+  std::string event_message = "event";
+  breadcrumb_manager_.AddEvent(event_message);
+  std::list<std::string> events = breadcrumb_manager_.GetEvents(0);
+  ASSERT_EQ(1ul, events.size());
+  // Events returned from |GetEvents| will have a timestamp prepended.
+  EXPECT_NE(std::string::npos, events.front().find(event_message));
+}
+
+// Tests that returned events returned by |GetEvents| are limited by the
+// |event_count_limit| parameter.
+TEST_F(BreadcrumbManagerTest, EventCountLimited) {
+  breadcrumb_manager_.AddEvent("event1");
+  breadcrumb_manager_.AddEvent("event2");
+  breadcrumb_manager_.AddEvent("event3");
+  breadcrumb_manager_.AddEvent("event4");
+
+  std::list<std::string> events = breadcrumb_manager_.GetEvents(2);
+  ASSERT_EQ(2ul, events.size());
+  EXPECT_NE(std::string::npos, events.front().find("event3"));
+  events.pop_front();
+  EXPECT_NE(std::string::npos, events.front().find("event4"));
+}
+
+// Tests that old events are dropped.
+TEST_F(BreadcrumbManagerTest, OldEventsDropped) {
+  // Log an event from one and two hours ago.
+  breadcrumb_manager_.AddEvent("event1");
+  task_env_.FastForwardBy(base::TimeDelta::FromHours(1));
+  breadcrumb_manager_.AddEvent("event2");
+  task_env_.FastForwardBy(base::TimeDelta::FromHours(1));
+
+  // Log three events separated by three minutes to ensure they receive their
+  // own event bucket. Otherwise, some old events may be returned to ensure a
+  // minimum number of available events. See |MinimumEventsReturned| test below.
+  breadcrumb_manager_.AddEvent("event3");
+  task_env_.FastForwardBy(base::TimeDelta::FromMinutes(3));
+  breadcrumb_manager_.AddEvent("event4");
+  task_env_.FastForwardBy(base::TimeDelta::FromMinutes(3));
+  breadcrumb_manager_.AddEvent("event5");
+
+  std::list<std::string> events = breadcrumb_manager_.GetEvents(0);
+  ASSERT_EQ(3ul, events.size());
+  // Validate the three most recent events are the ones which were returned.
+  EXPECT_NE(std::string::npos, events.front().find("event3"));
+  events.pop_front();
+  EXPECT_NE(std::string::npos, events.front().find("event4"));
+  events.pop_front();
+  EXPECT_NE(std::string::npos, events.front().find("event5"));
+}
+
+// Tests that expired events are returned if not enough new events exist.
+TEST_F(BreadcrumbManagerTest, MinimumEventsReturned) {
+  // Log an event from one and two hours ago.
+  breadcrumb_manager_.AddEvent("event1");
+  task_env_.FastForwardBy(base::TimeDelta::FromHours(1));
+  breadcrumb_manager_.AddEvent("event2");
+  task_env_.FastForwardBy(base::TimeDelta::FromHours(1));
+  breadcrumb_manager_.AddEvent("event3");
+
+  std::list<std::string> events = breadcrumb_manager_.GetEvents(0);
+  EXPECT_EQ(2ul, events.size());
+}

ios/chrome/test/BUILD.gn

@@ -165,6 +165,7 @@ test("ios_chrome_unittests") {
     "//ios/chrome/browser/browsing_data:unit_tests",
     "//ios/chrome/browser/complex_tasks:unit_tests",
     "//ios/chrome/browser/crash_report:unit_tests",
+    "//ios/chrome/browser/crash_report/breadcrumbs:unit_tests",
     "//ios/chrome/browser/device_sharing:unit_tests",
     "//ios/chrome/browser/download:unit_tests",
     "//ios/chrome/browser/drag_and_drop:unit_tests",