Move mod_pagespeed metrics out of prerender.

chrome/browser/mod_pagespeed_metrics.cc

Index: chrome/browser/mod_pagespeed_metrics.cc
diff --git a/chrome/browser/mod_pagespeed_metrics.cc b/chrome/browser/mod_pagespeed_metrics.cc
new file mode 100644
index 0000000000000000000000000000000000000000..443f7b2910f51e196f8e8259fb8f8bb363cf07a4
--- /dev/null
+++ b/chrome/browser/mod_pagespeed_metrics.cc
@@ -0,0 +1,137 @@
+// Copyright 2015 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/mod_pagespeed_metrics.h"
+
+#include <stdio.h>
+
+#include <string>
+
+#include "base/metrics/histogram.h"
+#include "base/metrics/sparse_histogram.h"
+#include "net/http/http_response_headers.h"
+#include "url/gurl.h"
+
+namespace {
+
+const char kModPagespeedHeader[] = "X-Mod-Pagespeed";
+const char kPageSpeedHeader[] = "X-Page-Speed";
+
+// For historical reasons, mod_pagespeed usage metrics are named with a
+// prerender prefix.
+const char kPagespeedServerHistogram[] =
+    "Prerender.PagespeedHeader.ServerCounts";
+const char kPagespeedVersionHistogram[] =
+    "Prerender.PagespeedHeader.VersionCounts";
+
+enum PagespeedHeaderServerType {
+  PAGESPEED_TOTAL_RESPONSES = 0,
+  PAGESPEED_MOD_PAGESPEED_SERVER = 1,
+  PAGESPEED_NGX_PAGESPEED_SERVER = 2,
+  PAGESPEED_PAGESPEED_SERVICE_SERVER = 3,
+  PAGESPEED_UNKNOWN_SERVER = 4,
+  PAGESPEED_SERVER_MAXIMUM = 5
+};
+
+// Parse the PageSpeed version number and encodes it in buckets 2 through 99:
+// if it is in the format a.b.c.d-e the bucket will be 2 + 2 * (max(c, 10) -
+// 10) + (d > 1 ? 1 : 0); otherwise the bucket is zero.
+int GetXModPagespeedBucketFromVersion(const std::string& version) {
+  int a, b, c, d, e;

[sky, 2015/03/31 23:51:55]

I realize you're just moving code, but since you're touching it you get
feedback. Please use descriptive names here. Also, using unused_ might be
helpful to indicate some fields aren't important.

[davidben, 2015/04/08 21:07:46]

Done.

+  int num_parsed =
+      sscanf(version.c_str(), "%d.%d.%d.%d-%d", &a, &b, &c, &d, &e);
+  int output = 0;
+  if (num_parsed == 5) {
+    output = 2;
+    if (c > 10)
+      output += 2 * (c - 10);
+    if (d > 1)
+      output++;
+    if (output < 2 || output > 99)
+      output = 0;
+  }
+  return output;
+}
+
+// Parse the X-Page-Speed header value and determine whether it is in the
+// PageSpeed Service format, namely m_n_dc were m_n is a version number and dc
+// is an encoded 2-character value.
+bool IsPageSpeedServiceVersionNumber(const std::string& version) {
+  int a, b;
+  char c, d, e;  // e is to detect EOL as we check that it /isn't/ converted.
+  int num_parsed = sscanf(version.c_str(), "%d_%d_%c%c%c", &a, &b, &c, &d, &e);
+  return (num_parsed == 4);
+}
+
+}  // namespace
+
+void RecordModPagespeedMetrics(
+    const content::ResourceType resource_type,
+    const GURL& request_url,
+    const net::HttpResponseHeaders* response_headers) {
+  if (resource_type != content::RESOURCE_TYPE_MAIN_FRAME ||
+      !request_url.SchemeIsHTTPOrHTTPS()) {
+    return;
+  }
+
+  // Bucket 0 counts every response seen.
+  UMA_HISTOGRAM_ENUMERATION(kPagespeedServerHistogram,
+                            PAGESPEED_TOTAL_RESPONSES,
+                            PAGESPEED_SERVER_MAXIMUM);
+  if (!response_headers)
+    return;
+
+  void* iter = NULL;

[sky, 2015/03/31 23:51:55]

nullptr

[davidben, 2015/04/08 21:07:45]

Done.

+  std::string name;
+  std::string value;
+  while (response_headers->EnumerateHeaderLines(&iter, &name, &value)) {
+    if (name == kModPagespeedHeader) {
+      // Bucket 1 counts occurrences of the X-Mod-Pagespeed header.
+      UMA_HISTOGRAM_ENUMERATION(kPagespeedServerHistogram,
+                                PAGESPEED_MOD_PAGESPEED_SERVER,
+                                PAGESPEED_SERVER_MAXIMUM);
+      if (!value.empty()) {
+        // If the header value is in the X-Mod-Pagespeed version number format
+        // then increment the appropriate bucket, otherwise increment bucket 1,
+        // which is the catch-all "unknown version number" bucket.
+        int bucket = GetXModPagespeedBucketFromVersion(value);
+        if (bucket > 0) {
+          UMA_HISTOGRAM_SPARSE_SLOWLY(kPagespeedVersionHistogram, bucket);
+        } else {
+          UMA_HISTOGRAM_SPARSE_SLOWLY(kPagespeedVersionHistogram, 1);
+        }
+      }
+      break;
+    } else if (name == kPageSpeedHeader) {
+      // X-Page-Speed header versions are either in the X-Mod-Pagespeed format,
+      // indicating an nginx installation, or they're in the PageSpeed Service
+      // format, indicating a PSS installation, or in some other format,
+      // indicating an unknown installation [possibly IISpeed].
+      if (!value.empty()) {
+        int bucket = GetXModPagespeedBucketFromVersion(value);
+        if (bucket > 0) {
+          // Bucket 2 counts occurences of the X-Page-Speed header with a
+          // value in the X-Mod-Pagespeed version number format. We also
+          // count these responses in the version histogram.
+          UMA_HISTOGRAM_ENUMERATION(kPagespeedServerHistogram,
+                                    PAGESPEED_NGX_PAGESPEED_SERVER,
+                                    PAGESPEED_SERVER_MAXIMUM);
+          UMA_HISTOGRAM_SPARSE_SLOWLY(kPagespeedVersionHistogram, bucket);
+        } else if (IsPageSpeedServiceVersionNumber(value)) {
+          // Bucket 3 counts occurences of the X-Page-Speed header with a
+          // value in the PageSpeed Service version number format.
+          UMA_HISTOGRAM_ENUMERATION(kPagespeedServerHistogram,
+                                    PAGESPEED_PAGESPEED_SERVICE_SERVER,
+                                    PAGESPEED_SERVER_MAXIMUM);
+        } else {
+          // Bucket 4 counts occurences of all other values.
+          UMA_HISTOGRAM_ENUMERATION(kPagespeedServerHistogram,
+                                    PAGESPEED_UNKNOWN_SERVER,
+                                    PAGESPEED_SERVER_MAXIMUM);
+        }
+      }
+      break;
+    }
+  }
+}