Use NetworkTrafficAnnotation in URLRequestContext UMA logging

net/url_request/url_request_context.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 "net/url_request/url_request_context.h"
 
 #include <inttypes.h>
+#include <limits>
 #include <utility>
 
 #include "base/compiler_specific.h"
 #include "base/debug/alias.h"
 #include "base/memory/ptr_util.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "base/trace_event/memory_allocator_dump.h"
@@ skipping 121 matching lines @@
   if (iter->second == 0)
     address_map_.erase(iter);
 }
 
 void URLRequestContext::InsertURLRequest(const URLRequest* request) const {
   url_requests_.insert(request);
   if (url_requests_.size() > largest_outstanding_requests_count_seen_) {
     largest_outstanding_requests_count_seen_ = url_requests_.size();
     UMA_HISTOGRAM_COUNTS_1M("Net.URLRequestContext.OutstandingRequests",
                             largest_outstanding_requests_count_seen_);
+    UMA_HISTOGRAM_ENUMERATION(
+        "Net.URLRequestContext.OutstandingRequests.Type",
+        request->traffic_annotation().unique_id_hash_code,
+        std::numeric_limits<base::HistogramBase::Sample>::max() - 1);

[mmenke, 2017/05/24 16:07:52]

Erm...wait...is this right?  SHould this be a sparse histogram or something?  I
think UMA_HISTOGRAM_ENUMERATION creates one bucket for every value?

[xunjieli, 2017/05/24 16:18:16]

I am not sure. I read the documentation on sparse histogram, but it says sparse
histogram is for histograms that are logged infrequently. Since
URLRequestContext::InsertURLRequest() is called for every network request, I am
not sure if that fits this use case.

+ asvitkine@
Alexei, I am adding a new histogram enum type, which is an unsigned int32. There
are about 100 of these values. What's the best way to log this data? 

[Alexei Svitkine (slow), 2017/05/24 17:13:29]

Do the values go outside of the signed int32 range? If not, the best way is to
use a sparse histogram. (UMA_HISTOGRAM_SPARSE()).

[xunjieli, 2017/05/24 17:23:02]

Thanks. 
+ rhalavati@, can we switch to signed int32 for hash code in your CL? 

   }
 }
 
 void URLRequestContext::RemoveURLRequest(const URLRequest* request) const {
   DCHECK_EQ(1u, url_requests_.count(request));
   url_requests_.erase(request);
 }
 
 void URLRequestContext::AssertNoURLRequests() const {
   int num_requests = url_requests_.size();
@@ skipping 37 matching lines @@
     HttpCache* http_cache = transaction_factory->GetCache();
     if (http_cache)
       http_cache->DumpMemoryStats(pmd, dump->absolute_name());
   }
   if (sdch_manager_)
     sdch_manager_->DumpMemoryStats(pmd, dump_name);
   return true;
 }
 
 }  // namespace net