org.htrace.Tracer Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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 org.htrace;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.htrace.impl.MilliSpan;
import java.security.SecureRandom;
import java.util.List;
import java.util.Random;
import java.util.concurrent.CopyOnWriteArrayList;
/**
* A Tracer provides the implementation for collecting and distributing Spans
* within a process.
*/
public class Tracer {
public static final Log LOG = LogFactory.getLog(Tracer.class);
private final static Random random = new SecureRandom();
private final List receivers = new CopyOnWriteArrayList();
private static final ThreadLocal currentSpan = new ThreadLocal() {
@Override
protected Span initialValue() {
return null;
}
};
public static final TraceInfo DONT_TRACE = new TraceInfo(-1, -1);
protected static String processId = null;
/**
* Internal class for defered singleton idiom.
*
* https://en.wikipedia.org/wiki/Initialization_on_demand_holder_idiom
*/
private static class TracerHolder {
private static final Tracer INSTANCE = new Tracer();
}
public static Tracer getInstance() {
return TracerHolder.INSTANCE;
}
protected Span createNew(String description) {
Span parent = currentSpan.get();
if (parent == null) {
return new MilliSpan(description,
/* traceId = */ random.nextLong(),
/* parentSpanId = */ Span.ROOT_SPAN_ID,
/* spanId = */ random.nextLong(),
getProcessId());
} else {
return parent.child(description);
}
}
protected boolean isTracing() {
return currentSpan.get() != null;
}
protected Span currentSpan() {
return currentSpan.get();
}
public void deliver(Span span) {
for (SpanReceiver receiver : receivers) {
receiver.receiveSpan(span);
}
}
protected void addReceiver(SpanReceiver receiver) {
receivers.add(receiver);
}
protected void removeReceiver(SpanReceiver receiver) {
receivers.remove(receiver);
}
protected Span setCurrentSpan(Span span) {
currentSpan.set(span);
return span;
}
public TraceScope continueSpan(Span s) {
Span oldCurrent = currentSpan();
setCurrentSpan(s);
return new TraceScope(s, oldCurrent);
}
protected int numReceivers() {
return receivers.size();
}
static String getProcessId() {
if (processId == null) {
String cmdLine = System.getProperty("sun.java.command");
if (cmdLine != null && !cmdLine.isEmpty()) {
String fullClassName = cmdLine.split("\\s+")[0];
String[] classParts = fullClassName.split("\\.");
cmdLine = classParts[classParts.length - 1];
}
processId = (cmdLine == null || cmdLine.isEmpty()) ? "Unknown" : cmdLine;
}
return processId;
}
}
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