Added tracking of time spent waiting on extensions to the webRequest API.

chrome/browser/extensions/extension_webrequest_time_tracker.cc

+// Copyright (c) 2011 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 "chrome/browser/extensions/extension_webrequest_time_tracker.h"
+
+#include "base/metrics/histogram.h"
+
+// TODO(mpcomplete): tweak all these constants.
+namespace {
+// The number of requests we keep track of at a time.
+const size_t kMaxRequestsLogged = 100u;
+
+// If a request completes faster than this amount (in ms), then we ignore it.
+// Any delays on such a request was negligible.
+const int kMinRequestTimeToCareMs = 10;
+
+// Thresholds above which we consider a delay caused by an extension to be "too
+// much". This is given in percentage of total request time that was spent
+// waiting on the extension.
+const double kThresholdModerateDelay = 0.20;
+const double kThresholdExcessiveDelay = 0.50;
+
+// If this many requests (of the past kMaxRequestsLogged) have had "too much"
+// delay, then we will warn the user.
+const size_t kNumModerateDelaysBeforeWarning = 50u;
+const size_t kNumExcessiveDelaysBeforeWarning = 10u;
+}  // namespace
+
+ExtensionWebRequestTimeTracker::RequestTimeLog::RequestTimeLog()
+    : completed(false) {
+}
+
+ExtensionWebRequestTimeTracker::RequestTimeLog::~RequestTimeLog() {
+}
+
+ExtensionWebRequestTimeTracker::ExtensionWebRequestTimeTracker() {
+}
+
+ExtensionWebRequestTimeTracker::~ExtensionWebRequestTimeTracker() {
+}
+
+void ExtensionWebRequestTimeTracker::LogRequestStartTime(
+    int64 request_id, const base::Time& start_time, const GURL& url) {
+  // Trim old completed request logs.
+  while (request_ids_.size() > kMaxRequestsLogged) {
+    int64 to_remove = request_ids_.front();
+    request_ids_.pop();
+    std::map<int64, RequestTimeLog>::iterator iter =
+        request_time_logs_.find(to_remove);
+    if (iter != request_time_logs_.end() && iter->second.completed) {
+      request_time_logs_.erase(iter);
+      moderate_delays_.erase(to_remove);
+      excessive_delays_.erase(to_remove);
+    }
+  }
+  request_ids_.push(request_id);
+
+  if (request_time_logs_.find(request_id) != request_time_logs_.end()) {
+    RequestTimeLog& log = request_time_logs_[request_id];
+    DCHECK(!log.completed);
+    return;
+  }
+  RequestTimeLog& log = request_time_logs_[request_id];
+  log.request_start_time = start_time;
+  log.url = url;
+}
+
+void ExtensionWebRequestTimeTracker::LogRequestEndTime(
+    int64 request_id, const base::Time& end_time) {
+  if (request_time_logs_.find(request_id) == request_time_logs_.end())
+    return;
+
+  RequestTimeLog& log = request_time_logs_[request_id];
+  if (log.completed)
+    return;
+
+  log.request_duration = end_time - log.request_start_time;
+  log.completed = true;
+
+  if (log.extension_block_durations.empty())
+    return;
+
+  HISTOGRAM_TIMES("Extensions.NetworkDelay", log.block_duration);
+
+  Analyze(request_id);
+}
+
+void ExtensionWebRequestTimeTracker::Analyze(int64 request_id) {
+  RequestTimeLog& log = request_time_logs_[request_id];
+
+  // Ignore really short requests. Time spent on these is negligible, and any
+  // extra delay the extension adds is likely to be noise.
+  if (log.request_duration.InMilliseconds() < kMinRequestTimeToCareMs)
+    return;
+
+  double percentage =
+      log.block_duration.InMillisecondsF() /
+      log.request_duration.InMillisecondsF();
+  LOG(ERROR) << "WR percent " << request_id << ": " << log.url << ": " <<
+      log.block_duration.InMilliseconds() << "/" <<
+      log.request_duration.InMilliseconds() << " = " << percentage;
+
+  // TODO(mpcomplete): need actual UI for the warning.
+  // TODO(mpcomplete): blame a specific extension. Maybe go through the list
+  // of recent requests and find the extension that has caused the most delays.
+  if (percentage > kThresholdExcessiveDelay) {
+    excessive_delays_.insert(request_id);
+    if (excessive_delays_.size() > kNumExcessiveDelaysBeforeWarning) {
+      LOG(ERROR) << "WR excessive delays:" << excessive_delays_.size();
+    }
+  } else if (percentage > kThresholdModerateDelay) {
+    moderate_delays_.insert(request_id);
+    if (moderate_delays_.size() > kNumModerateDelaysBeforeWarning) {
+      LOG(ERROR) << "WR moderate delays:" << moderate_delays_.size();
+    }
+  }
+}
+
+void ExtensionWebRequestTimeTracker::IncrementExtensionBlockTime(
+    const std::string& extension_id,
+    int64 request_id,
+    const base::TimeDelta& block_time) {
+  if (request_time_logs_.find(request_id) == request_time_logs_.end())
+    return;
+  RequestTimeLog& log = request_time_logs_[request_id];
+  log.extension_block_durations[extension_id] += block_time;
+}
+
+void ExtensionWebRequestTimeTracker::IncrementTotalBlockTime(
+    int64 request_id,
+    const base::TimeDelta& block_time) {
+  if (request_time_logs_.find(request_id) == request_time_logs_.end())
+    return;
+  RequestTimeLog& log = request_time_logs_[request_id];
+  log.block_duration += block_time;
+}
+
+void ExtensionWebRequestTimeTracker::SetRequestCanceled(int64 request_id) {
+  // Canceled requests won't actually hit the network, so we can't compare
+  // their request time to the time spent waiting on the extension. Just ignore
+  // them.
+  // TODO(mpcomplete): may want to count cancels as "bonuses" for an extension.
+  // i.e. if it slows down 50% of requests but cancels 25% of the rest, that
+  // might average out to only being "25% slow".
+  request_time_logs_.erase(request_id);
+}
+
+void ExtensionWebRequestTimeTracker::SetRequestRedirected(int64 request_id) {
+  // When a request is redirected, we have no way of knowing how long the
+  // request would have taken, so we can't say how much an extension slowed
+  // down this request. Just ignore it.
+  request_time_logs_.erase(request_id);
+}