Add in some infrastructure to make tracing of logical requests broken over async callbacks easier.

Create a concept of a TraceContext that holds a current Tracer which can be
used to create a timeseries sequence of events.

This implementation extends the functionality of RunnableMethod and
NewRunnableMethod() to create a parallel TracedMethod, and NewTracedMethod().
These new Traced methods methods and types know how to propogate the current
TraceContext to create a logical sequence of annotations through the servicing
of one logical action.

Currently, the code is controlled via define macro which changes
NewTracedMethod back into NewRunnableMethod if the hook is disabled.

BUG=52883
TEST=compiles, and client can connect to host.

Review URL: http://codereview.chromium.org/3169047

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@57992 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 144 insertions, 0 deletions

diff --git a/remoting/base/tracer.cc b/remoting/base/tracer.cc
new file mode 100644
index 0000000..c9df2f0
--- /dev/null
+++ b/remoting/base/tracer.cc
@@ -0,0 +1,144 @@
+// Copyright (c) 2010 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 "remoting/base/tracer.h"
+
+#include <list>
+
+#include "base/basictypes.h"
+#include "base/condition_variable.h"
+#include "base/message_loop.h"
+#include "base/rand_util.h"
+#include "base/ref_counted.h"
+#include "base/stl_util-inl.h"
+#include "base/thread.h"
+#include "base/time.h"
+
+namespace remoting {
+
+namespace {
+
+class OutputLogger {
+ public:
+  OutputLogger()
+      : thread_("logging_thread"),
+        stopped_(false),
+        wake_(&lock_) {
+    thread_.Start();
+    thread_.message_loop()->PostTask(
+        FROM_HERE,
+        NewRunnableMethod(this, &OutputLogger::PrintLogs));
+  }
+
+  void OutputTrace(TraceBuffer* buffer) {
+    scoped_ptr<TraceBuffer> buffer_ref_(buffer);
+    AutoLock l(lock_);
+
+    // Drop messages if we're overwhelming the logger.
+    if (buffers_.size() < 10) {
+      buffers_.push_front(buffer_ref_.release());
+      wake_.Signal();
+    } else {
+      // TODO(ajwong): Remove this cause it just overwhelms the logging more.
+      LOG(WARNING) << "Message dropped.";
+    }
+  }
+
+  void LogOneTrace(TraceBuffer* buffer) {
+    LOG(INFO) << "Trace: " << buffer->name();
+    base::Time last_timestamp;
+    for (int i = 0; i < buffer->record_size(); ++i) {
+      const TraceRecord& record = buffer->record(i);
+      base::Time timestamp = base::Time::FromInternalValue(record.timestamp());
+      if (i == 0) {
+        LOG(INFO) << "  TS: " << record.timestamp()
+                  << " msg: " << record.annotation();
+      } else {
+        base::TimeDelta delta = timestamp - last_timestamp;
+        LOG(INFO) << "  TS: " << record.timestamp()
+                  << " msg: " << record.annotation()
+                  << " [ " << delta.InMilliseconds() << "ms ]";
+      }
+      last_timestamp = timestamp;
+    }
+  }
+
+  void PrintLogs() {
+    while(!stopped_) {
+      TraceBuffer* buffer = NULL;
+      {
+        AutoLock l(lock_);
+        if (buffers_.size() == 0) {
+          wake_.Wait();
+        }
+        // Check again since we might have woken for a stop signal.
+        if (buffers_.size() != 0) {
+          buffer = buffers_.back();
+          buffers_.pop_back();
+        }
+      }
+
+      if (buffer) {
+        LogOneTrace(buffer);
+        delete buffer;
+      }
+    }
+  }
+
+ private:
+  friend struct DefaultSingletonTraits<OutputLogger>;
+
+  ~OutputLogger() {
+    {
+      AutoLock l(lock_);
+      stopped_ = true;
+      wake_.Signal();
+    }
+
+    thread_.Stop();
+    STLDeleteElements(&buffers_);
+  }
+
+  Lock lock_;
+  base::Thread thread_;
+  bool stopped_;
+  ConditionVariable wake_;
+  std::list<TraceBuffer*> buffers_;
+};
+
+}  // namespace
+
+Tracer::Tracer(const std::string& name, double sample_percent) {
+  if (sample_percent > base::RandDouble()) {
+    buffer_.reset(new TraceBuffer());
+    buffer_->set_name(name);
+  }
+}
+
+void Tracer::PrintString(const std::string& s) {
+  AutoLock l(lock_);
+  if (!buffer_.get()) {
+    return;
+  }
+
+  TraceRecord* record = buffer_->add_record();
+  record->set_annotation(s);
+  record->set_timestamp(base::Time::Now().ToInternalValue());
+
+  // Take the pointer for the current messageloop as identifying for the
+  // current thread.
+  record->set_thread_id(static_cast<uint64>(PlatformThread::CurrentId()));
+}
+
+Tracer::~Tracer() {
+  AutoLock l(lock_);
+
+  if (buffer_.get()) {
+    Singleton<OutputLogger>::get()->OutputTrace(buffer_.release());
+  }
+}
+
+}  // namespace remoting
+
+DISABLE_RUNNABLE_METHOD_REFCOUNT(remoting::OutputLogger);