FileContext.java
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上传日期:2018-01-08
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- /*
- * FileContext.java
- *
- * 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.file;
- import java.io.BufferedOutputStream;
- import java.io.File;
- import java.io.FileWriter;
- import java.io.IOException;
- import java.io.PrintWriter;
- import org.apache.hadoop.metrics.ContextFactory;
- import org.apache.hadoop.metrics.MetricsException;
- import org.apache.hadoop.metrics.spi.AbstractMetricsContext;
- import org.apache.hadoop.metrics.spi.OutputRecord;
- /**
- * Metrics context for writing metrics to a file.<p/>
- *
- * This class is configured by setting ContextFactory attributes which in turn
- * are usually configured through a properties file. All the attributes are
- * prefixed by the contextName. For example, the properties file might contain:
- * <pre>
- * myContextName.fileName=/tmp/metrics.log
- * myContextName.period=5
- * </pre>
- */
- public class FileContext extends AbstractMetricsContext {
-
- /* Configuration attribute names */
- protected static final String FILE_NAME_PROPERTY = "fileName";
- protected static final String PERIOD_PROPERTY = "period";
-
- private File file = null; // file for metrics to be written to
- private PrintWriter writer = null;
-
- /** Creates a new instance of FileContext */
- public FileContext() {}
-
- public void init(String contextName, ContextFactory factory) {
- super.init(contextName, factory);
-
- String fileName = getAttribute(FILE_NAME_PROPERTY);
- if (fileName != null) {
- file = new File(fileName);
- }
-
- String periodStr = getAttribute(PERIOD_PROPERTY);
- if (periodStr != null) {
- int period = 0;
- try {
- period = Integer.parseInt(periodStr);
- } catch (NumberFormatException nfe) {
- }
- if (period <= 0) {
- throw new MetricsException("Invalid period: " + periodStr);
- }
- setPeriod(period);
- }
- }
- /**
- * Returns the configured file name, or null.
- */
- public String getFileName() {
- if (file == null) {
- return null;
- } else {
- return file.getName();
- }
- }
-
- /**
- * Starts or restarts monitoring, by opening in append-mode, the
- * file specified by the <code>fileName</code> attribute,
- * if specified. Otherwise the data will be written to standard
- * output.
- */
- public void startMonitoring()
- throws IOException
- {
- if (file == null) {
- writer = new PrintWriter(new BufferedOutputStream(System.out));
- } else {
- writer = new PrintWriter(new FileWriter(file, true));
- }
- super.startMonitoring();
- }
-
- /**
- * Stops monitoring, closing the file.
- * @see #close()
- */
- public void stopMonitoring() {
- super.stopMonitoring();
-
- if (writer != null) {
- writer.close();
- writer = null;
- }
- }
-
- /**
- * Emits a metrics record to a file.
- */
- public void emitRecord(String contextName, String recordName, OutputRecord outRec) {
- writer.print(contextName);
- writer.print(".");
- writer.print(recordName);
- String separator = ": ";
- for (String tagName : outRec.getTagNames()) {
- writer.print(separator);
- separator = ", ";
- writer.print(tagName);
- writer.print("=");
- writer.print(outRec.getTag(tagName));
- }
- for (String metricName : outRec.getMetricNames()) {
- writer.print(separator);
- separator = ", ";
- writer.print(metricName);
- writer.print("=");
- writer.print(outRec.getMetric(metricName));
- }
- writer.println();
- }
-
- /**
- * Flushes the output writer, forcing updates to disk.
- */
- public void flush() {
- writer.flush();
- }
- }