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/*
* Copyright 2017 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package android.webkit;
import android.annotation.CallbackExecutor;
import android.annotation.NonNull;
import android.annotation.Nullable;
import java.io.OutputStream;
import java.util.concurrent.Executor;
/**
* Manages tracing of WebViews. In particular provides functionality for the app
* to enable/disable tracing of parts of code and to collect tracing data.
* This is useful for profiling performance issues, debugging and memory usage
* analysis in production and real life scenarios.
* <p>
* The resulting trace data is sent back as a byte sequence in json format. This
* file can be loaded in "chrome://tracing" for further analysis.
* <p>
* Example usage:
* <pre class="prettyprint">
* TracingController tracingController = TracingController.getInstance();
* tracingController.start(new TraceConfig.Builder()
* .addCategories(CATEGORIES_WEB_DEVELOPER).build());
* [..]
* tracingController.stop(new FileOutputStream("trace.json"),
* Executors.newSingleThreadExecutor());
* </pre></p>
*/
public abstract class TracingController {
/**
* Returns the default TracingController instance. At present there is
* only one TracingController instance for all WebView instances,
* however this restriction may be relaxed in a future Android release.
*
* @return the default TracingController instance
*/
@NonNull
public static TracingController getInstance() {
return WebViewFactory.getProvider().getTracingController();
}
/**
* Starts tracing all webviews. Depending on the trace mode in traceConfig
* specifies how the trace events are recorded.
*
* For tracing modes {@link TracingConfig#RECORD_UNTIL_FULL} and
* {@link TracingConfig#RECORD_CONTINUOUSLY} the events are recorded
* using an internal buffer and flushed to the outputStream when
* {@link #stop(OutputStream, Executor)} is called.
*
* @param tracingConfig configuration options to use for tracing
* @throws IllegalStateException if the system is already tracing.
*/
public abstract void start(@NonNull TracingConfig tracingConfig);
/**
* Stops tracing and flushes tracing data to the specified outputStream.
*
* The data is sent to the specified output stream in json format typically
* in chunks by invoking {@link java.io.OutputStream#write(byte[])}. On completion
* the {@link java.io.OutputStream#close()} method is called.
*
* @param outputStream the output steam the tracing data will be sent to. If null
* the tracing data will be discarded.
* @param executor the {@link java.util.concurrent.Executor} on which the
* outputStream #write and #close methods will be invoked.
* @return false if the system was not tracing at the time of the call, true
* otherwise.
*/
public abstract boolean stop(@Nullable OutputStream outputStream,
@NonNull @CallbackExecutor Executor executor);
/** True if the system is tracing */
public abstract boolean isTracing();
}
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