/**
* 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.apache.hadoop.metrics;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import java.util.Map;
import java.util.TreeMap;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.http.HttpServer;
import org.apache.hadoop.metrics.spi.OutputRecord;
import org.apache.hadoop.metrics.spi.AbstractMetricsContext.MetricMap;
import org.apache.hadoop.metrics.spi.AbstractMetricsContext.TagMap;
import org.mortbay.util.ajax.JSON;
import org.mortbay.util.ajax.JSON.Output;
/**
* A servlet to print out metrics data. By default, the servlet returns a
* textual representation (no promises are made for parseability), and
* users can use "?format=json" for parseable output.
*/
@InterfaceAudience.Private
@InterfaceStability.Evolving
public class MetricsServlet extends HttpServlet {
/**
* A helper class to hold a TagMap and MetricMap.
*/
static class TagsMetricsPair implements JSON.Convertible {
final TagMap tagMap;
final MetricMap metricMap;
public TagsMetricsPair(TagMap tagMap, MetricMap metricMap) {
this.tagMap = tagMap;
this.metricMap = metricMap;
}
@SuppressWarnings("unchecked")
public void fromJSON(Map map) {
throw new UnsupportedOperationException();
}
/** Converts to JSON by providing an array. */
public void toJSON(Output out) {
out.add(new Object[] { tagMap, metricMap });
}
}
/**
* Collects all metric data, and returns a map:
* contextName -> recordName -> [ (tag->tagValue), (metric->metricValue) ].
* The values are either String or Number. The final value is implemented
* as a list of TagsMetricsPair.
*/
Map<String, Map<String, List<TagsMetricsPair>>> makeMap(
Collection<MetricsContext> contexts) throws IOException {
Map<String, Map<String, List<TagsMetricsPair>>> map =
new TreeMap<String, Map<String, List<TagsMetricsPair>>>();
for (MetricsContext context : contexts) {
Map<String, List<TagsMetricsPair>> records =
new TreeMap<String, List<TagsMetricsPair>>();
map.put(context.getContextName(), records);
for (Map.Entry<String, Collection<OutputRecord>> r :
context.getAllRecords().entrySet()) {
List<TagsMetricsPair> metricsAndTags =
new ArrayList<TagsMetricsPair>();
records.put(r.getKey(), metricsAndTags);
for (OutputRecord outputRecord : r.getValue()) {
TagMap tagMap = outputRecord.getTagsCopy();
MetricMap metricMap = outputRecord.getMetricsCopy();
metricsAndTags.add(new TagsMetricsPair(tagMap, metricMap));
}
}
}
return map;
}
@Override
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
if (!HttpServer.isInstrumentationAccessAllowed(getServletContext(),
request, response)) {
return;
}
String format = request.getParameter("format");
Collection<MetricsContext> allContexts =
ContextFactory.getFactory().getAllContexts();
if ("json".equals(format)) {
response.setContentType("application/json; charset=utf-8");
PrintWriter out = response.getWriter();
try {
// Uses Jetty's built-in JSON support to convert the map into JSON.
out.print(new JSON().toJSON(makeMap(allContexts)));
} finally {
out.close();
}
} else {
PrintWriter out = response.getWriter();
try {
printMap(out, makeMap(allContexts));
} finally {
out.close();
}
}
}
/**
* Prints metrics data in a multi-line text form.
*/
void printMap(PrintWriter out, Map<String, Map<String, List<TagsMetricsPair>>> map) {
for (Map.Entry<String, Map<String, List<TagsMetricsPair>>> context : map.entrySet()) {
out.print(context.getKey());
out.print("\n");
for (Map.Entry<String, List<TagsMetricsPair>> record : context.getValue().entrySet()) {
indent(out, 1);
out.print(record.getKey());
out.print("\n");
for (TagsMetricsPair pair : record.getValue()) {
indent(out, 2);
// Prints tag values in the form "{key=value,key=value}:"
out.print("{");
boolean first = true;
for (Map.Entry<String, Object> tagValue : pair.tagMap.entrySet()) {
if (first) {
first = false;
} else {
out.print(",");
}
out.print(tagValue.getKey());
out.print("=");
out.print(tagValue.getValue().toString());
}
out.print("}:\n");
// Now print metric values, one per line
for (Map.Entry<String, Number> metricValue :
pair.metricMap.entrySet()) {
indent(out, 3);
out.print(metricValue.getKey());
out.print("=");
out.print(metricValue.getValue().toString());
out.print("\n");
}
}
}
}
}
private void indent(PrintWriter out, int indent) {
for (int i = 0; i < indent; ++i) {
out.append(" ");
}
}
}