[Sync] Finch Experiment : Enable compression between sync client and server

sync/internal_api/http_bridge.cc

 // Copyright 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 "sync/internal_api/public/http_bridge.h"
 
 #include "base/message_loop/message_loop.h"
+#include "base/metrics/field_trial.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/stringprintf.h"
 #include "net/base/load_flags.h"
 #include "net/base/net_errors.h"
 #include "net/http/http_cache.h"
 #include "net/http/http_network_layer.h"
 #include "net/http/http_request_headers.h"
 #include "net/http/http_response_headers.h"
 #include "net/url_request/static_http_user_agent_settings.h"
@@ skipping 12 matching lines @@
 // treated as a transient failure.
 const int kMaxHttpRequestTimeSeconds = 60 * 5;  // 5 minutes.
 
 // Helper method for logging timeouts via UMA.
 void LogTimeout(bool timed_out) {
   UMA_HISTOGRAM_BOOLEAN("Sync.URLFetchTimedOut", timed_out);
 }
 
 }  // namespace
 
+bool IsSyncHttpContentCompressionEnabled() {
+  const std::string group_name =
+      base::FieldTrialList::FindFullName("SyncHttpContentCompression");
+  return group_name == "Enabled";
+}
+
+bool GZipCompress(std::string source, std::string* dest) {

[Alexei Svitkine (slow), 2015/07/25 15:50:36]

FYI: We have something similar here:

https://code.google.com/p/chromium/codesearch#chromium/src/components/metrics...

I wonder if we could re-use it somehow. Or at the very least to add a TODO to do
it at the time when this stops being an experiment.

[Gang Wu, 2015/07/27 22:35:06]

Thanks for info, I tried change to use metrics::GzipCompress, but got warning at
http://build.chromium.org/p/tryserver.chromium.mac/builders/ios_dbg_simulator...


Cycle: /b/build/slave/ios_rel_device_ninja/build/src/components/components.gyp
-> /b/build/slave/ios_rel_device_ninja/build/src/sync/sync.gyp ->
/b/build/slave/ios_rel_device_ninja/build/src/components/components.gyp

so I write our own function, actually, I like to use metrics's function, but do
you know how to avoid this cycle dependency?

+  z_stream stream = {0};
+  int result = deflateInit2(&stream, Z_DEFAULT_COMPRESSION, Z_DEFLATED,
+                            // 16 is added to produce a gzip header + trailer.
+                            MAX_WBITS + 16,
+                            8,  // memLevel = 8 is default.
+                            Z_DEFAULT_STRATEGY);
+  DCHECK_EQ(Z_OK, result);
+  size_t out_size = deflateBound(&stream, source.size());
+  scoped_ptr<char[]> out(new char[out_size]);
+
+  stream.next_in = reinterpret_cast<uint8*>(&source[0]);
+  stream.avail_in = source.size();
+  stream.next_out = reinterpret_cast<uint8*>(out.get());
+  stream.avail_out = out_size;
+
+  result = deflate(&stream, Z_FINISH);
+  if (result != Z_STREAM_END) {
+    return false;
+  }
+  out_size = out_size - stream.avail_out;
+
+  result = deflateEnd(&stream);
+  DCHECK_EQ(Z_OK, result);
+
+  dest->assign(out.get(), out_size);
+  return true;
+}
+
+void RecordSyncContentLengthHistograms(int64 this_content_length,
+                                       int64 this_original_content_length) {
+  // Upload UMA data
+  UMA_HISTOGRAM_COUNTS("Sync.ContentLengthCompressed", this_content_length);
+  UMA_HISTOGRAM_COUNTS("Sync.ContentLengthOriginal",
+                       this_original_content_length);
+}
+
 HttpBridgeFactory::HttpBridgeFactory(
     const scoped_refptr<net::URLRequestContextGetter>& request_context_getter,
     const NetworkTimeUpdateCallback& network_time_update_callback,
     CancelationSignal* cancelation_signal)
     : request_context_getter_(request_context_getter),
       network_time_update_callback_(network_time_update_callback),
       cancelation_signal_(cancelation_signal) {
   // Registration should never fail.  This should happen on the UI thread during
   // init.  It would be impossible for a shutdown to have been requested at this
   // point.
@@ skipping 146 matching lines @@
 
   // Start the timer on the network thread (the same thread progress is made
   // on, and on which the url fetcher lives).
   DCHECK(!fetch_state_.http_request_timeout_timer.get());
   fetch_state_.http_request_timeout_timer.reset(new base::Timer(false, false));
   fetch_state_.http_request_timeout_timer->Start(
       FROM_HERE, base::TimeDelta::FromSeconds(kMaxHttpRequestTimeSeconds),
       base::Bind(&HttpBridge::OnURLFetchTimedOut, this));
 
   DCHECK(request_context_getter_.get());
+  fetch_state_.start_time = base::Time::Now();
   fetch_state_.url_poster =
       net::URLFetcher::Create(url_for_request_, net::URLFetcher::POST, this)
           .release();
   fetch_state_.url_poster->SetRequestContext(request_context_getter_.get());
-  fetch_state_.url_poster->SetUploadData(content_type_, request_content_);
   fetch_state_.url_poster->SetExtraRequestHeaders(extra_headers_);
+
+  std::string content_to_be_sent = request_content_;
+  if (IsSyncHttpContentCompressionEnabled()) {
+    GZipCompress(request_content_, &content_to_be_sent);
+    fetch_state_.url_poster->AddExtraRequestHeader("Content-Encoding: gzip");
+  } else {
+    fetch_state_.url_poster->AddExtraRequestHeader("Accept-Encoding: deflate");
+  }
+  fetch_state_.url_poster->SetUploadData(content_type_, content_to_be_sent);
+  RecordSyncContentLengthHistograms(content_to_be_sent.size(),
+                                    request_content_.size());
+
   fetch_state_.url_poster->AddExtraRequestHeader(base::StringPrintf(
       "%s: %s", net::HttpRequestHeaders::kUserAgent, user_agent_.c_str()));
   fetch_state_.url_poster->SetLoadFlags(net::LOAD_BYPASS_CACHE |
                                         net::LOAD_DISABLE_CACHE |
                                         net::LOAD_DO_NOT_SAVE_COOKIES |
                                         net::LOAD_DO_NOT_SEND_COOKIES);
-  fetch_state_.start_time = base::Time::Now();
 
   fetch_state_.url_poster->Start();
 }
 
 int HttpBridge::GetResponseContentLength() const {
   DCHECK_EQ(base::MessageLoop::current(), created_on_loop_);
   base::AutoLock lock(fetch_state_lock_);
   DCHECK(fetch_state_.request_completed);
   return fetch_state_.response_content.size();
 }
@@ skipping 79 matching lines @@
   // Use a real (non-debug) log to facilitate troubleshooting in the wild.
   VLOG(2) << "HttpBridge::OnURLFetchComplete for: "
           << fetch_state_.url_poster->GetURL().spec();
   VLOG(1) << "HttpBridge received response code: "
           << fetch_state_.http_response_code;
 
   source->GetResponseAsString(&fetch_state_.response_content);
   fetch_state_.response_headers = source->GetResponseHeaders();
   UpdateNetworkTime();
 
+  int64 compressed_content_length = fetch_state_.response_content.size();
+  int64 original_content_length = compressed_content_length;
+  if (fetch_state_.response_headers &&
+      fetch_state_.response_headers->HasHeaderValue("content-encoding",
+                                                    "gzip")) {
+    compressed_content_length = fetch_state_.response_headers->GetContentLength();

[Alexei Svitkine (slow), 2015/07/25 15:50:36]

Nit: Line length

[Gang Wu, 2015/07/27 22:35:06]

Done.

+  }
+  RecordSyncContentLengthHistograms(compressed_content_length, original_content_length);
+
   // End of the line for url_poster_. It lives only on the IO loop.
   // We defer deletion because we're inside a callback from a component of the
   // URLFetcher, so it seems most natural / "polite" to let the stack unwind.
   base::MessageLoop::current()->DeleteSoon(FROM_HERE, fetch_state_.url_poster);
   fetch_state_.url_poster = NULL;
 
   // Wake the blocked syncer thread in MakeSynchronousPost.
   // WARNING: DONT DO ANYTHING AFTER THIS CALL! |this| may be deleted!
   http_post_completed_.Signal();
 }
@@ skipping 64 matching lines @@
   int64 sane_time_ms = 0;
   if (base::StringToInt64(sane_time_str, &sane_time_ms)) {
     network_time_update_callback_.Run(
         base::Time::FromJsTime(sane_time_ms),
         base::TimeDelta::FromMilliseconds(1),
         fetch_state_.end_time - fetch_state_.start_time);
   }
 }
 
 }  // namespace syncer