hadoop ReconfigurationServlet 源码
haddop ReconfigurationServlet 代码
文件路径：/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/conf/ReconfigurationServlet.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.conf;
import org.apache.commons.text.StringEscapeUtils;
import java.util.Collection;
import java.util.Enumeration;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.hadoop.util.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* A servlet for changing a node's configuration.
*
* Reloads the configuration file, verifies whether changes are
* possible and asks the admin to approve the change.
*
*/
public class ReconfigurationServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
private static final Logger LOG =
LoggerFactory.getLogger(ReconfigurationServlet.class);
// the prefix used to fing the attribute holding the reconfigurable
// for a given request
//
// we get the attribute prefix + servlet path
public static final String CONF_SERVLET_RECONFIGURABLE_PREFIX =
"conf.servlet.reconfigurable.";
@Override
public void init() throws ServletException {
super.init();
}
private Reconfigurable getReconfigurable(HttpServletRequest req) {
LOG.info("servlet path: " + req.getServletPath());
LOG.info("getting attribute: " + CONF_SERVLET_RECONFIGURABLE_PREFIX +
req.getServletPath());
return (Reconfigurable)
this.getServletContext().getAttribute(CONF_SERVLET_RECONFIGURABLE_PREFIX +
req.getServletPath());
}
private void printHeader(PrintWriter out, String nodeName) {
out.print("<html><head>");
out.printf("<title>%s Reconfiguration Utility</title>%n",
StringEscapeUtils.escapeHtml4(nodeName));
out.print("</head><body>\n");
out.printf("<h1>%s Reconfiguration Utility</h1>%n",
StringEscapeUtils.escapeHtml4(nodeName));
}
private void printFooter(PrintWriter out) {
out.print("</body></html>\n");
}
/**
* Print configuration options that can be changed.
*/
private void printConf(PrintWriter out, Reconfigurable reconf) {
Configuration oldConf = reconf.getConf();
Configuration newConf = new Configuration();
Collection<ReconfigurationUtil.PropertyChange> changes =
ReconfigurationUtil.getChangedProperties(newConf,
oldConf);
boolean changeOK = true;
out.println("<form action=\"\" method=\"post\">");
out.println("<table border=\"1\">");
out.println("<tr><th>Property</th><th>Old value</th>");
out.println("<th>New value </th><th></th></tr>");
for (ReconfigurationUtil.PropertyChange c: changes) {
out.print("<tr><td>");
if (!reconf.isPropertyReconfigurable(c.prop)) {
out.print("<font color=\"red\">" +
StringEscapeUtils.escapeHtml4(c.prop) + "</font>");
changeOK = false;
} else {
out.print(StringEscapeUtils.escapeHtml4(c.prop));
out.print("<input type=\"hidden\" name=\"" +
StringEscapeUtils.escapeHtml4(c.prop) + "\" value=\"" +
StringEscapeUtils.escapeHtml4(c.newVal) + "\"/>");
}
out.print("</td><td>" +
(c.oldVal == null ? "<it>default</it>" :
StringEscapeUtils.escapeHtml4(c.oldVal)) +
"</td><td>" +
(c.newVal == null ? "<it>default</it>" :
StringEscapeUtils.escapeHtml4(c.newVal)) +
"</td>");
out.print("</tr>\n");
}
out.println("</table>");
if (!changeOK) {
out.println("<p><font color=\"red\">WARNING: properties marked red" +
" will not be changed until the next restart.</font></p>");
}
out.println("<input type=\"submit\" value=\"Apply\" />");
out.println("</form>");
}
@SuppressWarnings("unchecked")
private Enumeration<String> getParams(HttpServletRequest req) {
return req.getParameterNames();
}
/**
* Apply configuratio changes after admin has approved them.
*/
private void applyChanges(PrintWriter out, Reconfigurable reconf,
HttpServletRequest req) throws ReconfigurationException {
Configuration oldConf = reconf.getConf();
Configuration newConf = new Configuration();
Enumeration<String> params = getParams(req);
synchronized(oldConf) {
while (params.hasMoreElements()) {
String rawParam = params.nextElement();
String param = StringEscapeUtils.unescapeHtml4(rawParam);
String value =
StringEscapeUtils.unescapeHtml4(req.getParameter(rawParam));
if (value != null) {
if (value.equals(newConf.getRaw(param)) || value.equals("default") ||
value.equals("null") || value.isEmpty()) {
if ((value.equals("default") || value.equals("null") ||
value.isEmpty()) &&
oldConf.getRaw(param) != null) {
out.println("<p>Changed \"" +
StringEscapeUtils.escapeHtml4(param) + "\" from \"" +
StringEscapeUtils.escapeHtml4(oldConf.getRaw(param)) +
"\" to default</p>");
reconf.reconfigureProperty(param, null);
} else if (!value.equals("default") && !value.equals("null") &&
!value.isEmpty() &&
(oldConf.getRaw(param) == null ||
!oldConf.getRaw(param).equals(value))) {
// change from default or value to different value
if (oldConf.getRaw(param) == null) {
out.println("<p>Changed \"" +
StringEscapeUtils.escapeHtml4(param) +
"\" from default to \"" +
StringEscapeUtils.escapeHtml4(value) + "\"</p>");
} else {
out.println("<p>Changed \"" +
StringEscapeUtils.escapeHtml4(param) + "\" from \"" +
StringEscapeUtils.escapeHtml4(oldConf.
getRaw(param)) +
"\" to \"" +
StringEscapeUtils.escapeHtml4(value) + "\"</p>");
}
reconf.reconfigureProperty(param, value);
} else {
LOG.info("property " + param + " unchanged");
}
} else {
// parameter value != newConf value
out.println("<p>\"" + StringEscapeUtils.escapeHtml4(param) +
"\" not changed because value has changed from \"" +
StringEscapeUtils.escapeHtml4(value) + "\" to \"" +
StringEscapeUtils.escapeHtml4(newConf.getRaw(param)) +
"\" since approval</p>");
}
}
}
}
}
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
LOG.info("GET");
resp.setContentType("text/html");
PrintWriter out = resp.getWriter();
Reconfigurable reconf = getReconfigurable(req);
String nodeName = reconf.getClass().getCanonicalName();
printHeader(out, nodeName);
printConf(out, reconf);
printFooter(out);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
LOG.info("POST");
resp.setContentType("text/html");
PrintWriter out = resp.getWriter();
Reconfigurable reconf = getReconfigurable(req);
String nodeName = reconf.getClass().getCanonicalName();
printHeader(out, nodeName);
try {
applyChanges(out, reconf, req);
} catch (ReconfigurationException e) {
resp.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR,
StringUtils.stringifyException(e));
return;
}
out.println("<p><a href=\"" + req.getServletPath() + "\">back</a></p>");
printFooter(out);
}
}
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