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// 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.
#ifndef CONTENT_PUBLIC_BROWSER_TRACE_CONTROLLER_H_
#define CONTENT_PUBLIC_BROWSER_TRACE_CONTROLLER_H_
#include "content/common/content_export.h"
namespace content {
class TraceSubscriber;
// TraceController is used on the browser processes to enable/disable
// trace status and collect trace data. Only the browser UI thread is allowed
// to interact with the TraceController object. All calls on the TraceSubscriber
// happen on the UI thread.
class TraceController {
public:
CONTENT_EXPORT static TraceController* GetInstance();
// Called by browser process to start tracing events on all processes.
//
// Currently only one subscriber is allowed at a time.
// Tracing begins immediately locally, and asynchronously on child processes
// as soon as they receive the BeginTracing request.
// By default, all categories are traced except those matching "test_*".
//
// If BeginTracing was already called previously,
// or if an EndTracingAsync is pending,
// or if another subscriber is tracing,
// BeginTracing will return false meaning it failed.
virtual bool BeginTracing(TraceSubscriber* subscriber) = 0;
// |categories| is a comma-delimited list of category wildcards.
// A category can have an optional '-' prefix to make it an excluded category.
// All the same rules apply above, so for example, having both included and
// excluded categories in the same list would not be supported.
//
// Example: BeginTracing("test_MyTest*");
// Example: BeginTracing("test_MyTest*,test_OtherStuff");
// Example: BeginTracing("-excluded_category1,-excluded_category2");
virtual bool BeginTracing(TraceSubscriber* subscriber,
const std::string& categories) = 0;
// Called by browser process to stop tracing events on all processes.
//
// Child processes typically are caching trace data and only rarely flush
// and send trace data back to the browser process. That is because it may be
// an expensive operation to send the trace data over IPC, and we would like
// to avoid much runtime overhead of tracing. So, to end tracing, we must
// asynchronously ask all child processes to flush any pending trace data.
//
// Once all child processes have acked the EndTracing request,
// TraceSubscriber will be called with OnEndTracingComplete.
//
// If a previous call to EndTracingAsync is already pending,
// or if another subscriber is tracing,
// EndTracingAsync will return false meaning it failed.
virtual bool EndTracingAsync(TraceSubscriber* subscriber) = 0;
// Get the maximum across processes of trace buffer percent full state.
// When the TraceBufferPercentFull value is determined,
// subscriber->OnTraceBufferPercentFullReply is called.
// When any child process reaches 100% full, the TraceController will end
// tracing, and call TraceSubscriber::OnEndTracingComplete.
// GetTraceBufferPercentFullAsync fails in the following conditions:
// trace is ending or disabled;
// a previous call to GetTraceBufferPercentFullAsync is pending; or
// the caller is not the current subscriber.
virtual bool GetTraceBufferPercentFullAsync(TraceSubscriber* subscriber) = 0;
// Cancel the subscriber so that it will not be called when EndTracingAsync is
// acked by all child processes. This will also call EndTracingAsync
// internally if necessary.
// Safe to call even if caller is not the current subscriber.
virtual void CancelSubscriber(TraceSubscriber* subscriber) = 0;
protected:
virtual ~TraceController() {}
};
} // namespace content
#endif // CONTENT_PUBLIC_BROWSER_TRACE_CONTROLLER_H_
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