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

sync/internal_api/http_bridge.cc

Index: sync/internal_api/http_bridge.cc
diff --git a/sync/internal_api/http_bridge.cc b/sync/internal_api/http_bridge.cc
index c64822d5836d2e729d6f7bca00069e5eebbd7c80..211af282f831c6140eafea82b5ce5631516f8cc7 100644
--- a/sync/internal_api/http_bridge.cc
+++ b/sync/internal_api/http_bridge.cc
@@ -5,6 +5,7 @@
 #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"
@@ -37,6 +38,49 @@ void LogTimeout(bool 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,
@@ -203,19 +247,30 @@ void HttpBridge::MakeAsynchronousPost() {
       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();
 }
@@ -315,6 +370,15 @@ void HttpBridge::OnURLFetchComplete(const net::URLFetcher* source) {
   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.