HADOOP-6408. Add a /conf servlet to dump running configuration. Contributed by Todd Lipcon.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@896641 13f79535-47bb-0310-9956-ffa450edef68

CHANGES.txt

@@ -35,6 +35,9 @@ Trunk (unreleased changes)
 
     HADOOP-6466. Add a ZooKeeper service to the cloud scripts. (tomwhite)
 
+    HADOOP-6408. Add a /conf servlet to dump running configuration.
+    (Todd Lipcon via tomwhite)
+
   IMPROVEMENTS
 
     HADOOP-6283. Improve the exception messages thrown by

src/java/org/apache/hadoop/conf/ConfServlet.java

@@ -0,0 +1,97 @@
+/**
+ * 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 java.io.IOException;
+import java.io.OutputStreamWriter;
+import java.io.Writer;
+
+import javax.servlet.ServletException;
+import javax.servlet.http.HttpServlet;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+
+import org.apache.hadoop.http.HttpServer;
+
+/**
+ * A servlet to print out the running configuration data.
+ */
+public class ConfServlet extends HttpServlet {
+  private static final long serialVersionUID = 1L;
+
+  private static final String FORMAT_JSON = "json";
+  private static final String FORMAT_XML = "xml";
+  private static final String FORMAT_PARAM = "format";
+
+  /**
+   * Return the Configuration of the daemon hosting this servlet.
+   * This is populated when the HttpServer starts.
+   */
+  private Configuration getConfFromContext() {
+    Configuration conf = (Configuration)getServletContext().getAttribute(
+        HttpServer.CONF_CONTEXT_ATTRIBUTE);
+    assert conf != null;
+    return conf;
+  }
+
+  @Override
+  public void doGet(HttpServletRequest request, HttpServletResponse response)
+      throws ServletException, IOException {
+    String format = request.getParameter(FORMAT_PARAM);
+    if (null == format) {
+      format = FORMAT_XML;
+    }
+
+    if (FORMAT_XML.equals(format)) {
+      response.setContentType("text/xml");
+    } else if (FORMAT_JSON.equals(format)) {
+      response.setContentType("text/javascript");
+    }
+
+    OutputStreamWriter out = new OutputStreamWriter(response.getOutputStream());
+    try {
+      writeResponse(getConfFromContext(), out, format);
+    } catch (BadFormatException bfe) {
+      response.sendError(HttpServletResponse.SC_BAD_REQUEST, bfe.getMessage());
+    }
+    out.close();
+  }
+
+  /**
+   * Guts of the servlet - extracted for easy testing.
+   */
+  static void writeResponse(Configuration conf, Writer out, String format)
+    throws IOException, BadFormatException {
+    if (FORMAT_JSON.equals(format)) {
+      Configuration.dumpConfiguration(conf, out);
+    } else if (FORMAT_XML.equals(format)) {
+      conf.writeXml(out);
+    } else {
+      throw new BadFormatException("Bad format: " + format);
+    }
+  }
+
+  public static class BadFormatException extends Exception {
+    private static final long serialVersionUID = 1L;
+
+    public BadFormatException(String msg) {
+      super(msg);
+    }
+  }
+
+}

src/java/org/apache/hadoop/conf/Configuration.java

@@ -27,6 +27,7 @@ import java.io.IOException;
 import java.io.InputStream;
 import java.io.InputStreamReader;
 import java.io.OutputStream;
+import java.io.OutputStreamWriter;
 import java.io.Reader;
 import java.io.Writer;
 import java.net.URL;
@@ -53,6 +54,7 @@ import javax.xml.parsers.DocumentBuilder;
 import javax.xml.parsers.DocumentBuilderFactory;
 import javax.xml.parsers.ParserConfigurationException;
 import javax.xml.transform.Transformer;
+import javax.xml.transform.TransformerException;
 import javax.xml.transform.TransformerFactory;
 import javax.xml.transform.dom.DOMSource;
 import javax.xml.transform.stream.StreamResult;
@@ -68,6 +70,7 @@ import org.apache.hadoop.util.ReflectionUtils;
 import org.apache.hadoop.util.StringUtils;
 import org.codehaus.jackson.JsonFactory;
 import org.codehaus.jackson.JsonGenerator;
+import org.w3c.dom.Comment;
 import org.w3c.dom.DOMException;
 import org.w3c.dom.Document;
 import org.w3c.dom.Element;
@@ -153,6 +156,12 @@ public class Configuration implements Iterable<Map.Entry<String,String>>,
    */
   private ArrayList<Object> resources = new ArrayList<Object>();
 
+  /**
+   * The value reported as the setting resource when a key is set
+   * by code rather than a file resource.
+   */
+  static final String UNKNOWN_RESOURCE = "Unknown";
+
   /**
    * List of configuration parameters marked <b>final</b>. 
    */
@@ -175,13 +184,7 @@ public class Configuration implements Iterable<Map.Entry<String,String>>,
 
   private static final Map<ClassLoader, Map<String, Class<?>>>
     CACHE_CLASSES = new WeakHashMap<ClassLoader, Map<String, Class<?>>>();
-  
-  /**
-   * Flag to indicate if the storage of resource which updates a key needs 
-   * to be stored for each key
-   */
-  private boolean storeResource;
-  
+
   /**
    * Stores the mapping of key to the resource which modifies or loads 
    * the key most recently
@@ -385,26 +388,10 @@ public class Configuration implements Iterable<Map.Entry<String,String>>,
    */
   public Configuration(boolean loadDefaults) {
     this.loadDefaults = loadDefaults;
+    updatingResource = new HashMap<String, String>();
     synchronized(Configuration.class) {
       REGISTRY.put(this, null);
     }
-    this.storeResource = false;
-  }
-  
-  /**
-   * A new configuration with the same settings and additional facility for
-   * storage of resource to each key which loads or updates 
-   * the key most recently
-   * @param other the configuration from which to clone settings
-   * @param storeResource flag to indicate if the storage of resource to 
-   * each key is to be stored
-   */
-  private Configuration(Configuration other, boolean storeResource) {
-    this(other);
-    this.storeResource = storeResource;
-    if (storeResource) {
-      updatingResource = new HashMap<String, String>();
-    }
   }
   
   /** 
@@ -423,6 +410,8 @@ public class Configuration implements Iterable<Map.Entry<String,String>>,
      if (other.overlay!=null) {
        this.overlay = (Properties)other.overlay.clone();
      }
+
+     this.updatingResource = new HashMap<String, String>(other.updatingResource);
    }
    
     this.finalParameters = new HashSet<String>(other.finalParameters);
@@ -604,6 +593,7 @@ public class Configuration implements Iterable<Map.Entry<String,String>>,
     if (!isDeprecated(name)) {
       getOverlay().setProperty(name, value);
       getProps().setProperty(name, value);
+      updatingResource.put(name, UNKNOWN_RESOURCE);
     }
     else {
       DeprecatedKeyInfo keyInfo = deprecatedKeyMap.get(name);
@@ -1352,10 +1342,8 @@ public class Configuration implements Iterable<Map.Entry<String,String>>,
       loadResources(properties, resources, quietmode);
       if (overlay!= null) {
         properties.putAll(overlay);
-        if (storeResource) {
-          for (Map.Entry<Object,Object> item: overlay.entrySet()) {
-            updatingResource.put((String) item.getKey(), "Unknown");
-          }
+        for (Map.Entry<Object,Object> item: overlay.entrySet()) {
+          updatingResource.put((String) item.getKey(), UNKNOWN_RESOURCE);
         }
       }
     }
@@ -1438,9 +1426,7 @@ public class Configuration implements Iterable<Map.Entry<String,String>>,
       if (finalParameters.contains(oldKey)) {
         finalParameters.remove(oldKey);
       }
-      if (storeResource) {
-        updatingResource.remove(oldKey);
-      }
+      updatingResource.remove(oldKey);
     }
   }
   
@@ -1464,9 +1450,7 @@ public class Configuration implements Iterable<Map.Entry<String,String>>,
         continue;
       }
       properties.setProperty(key, value);
-      if (storeResource) {
-        updatingResource.put(key, updatingResource.get(attr));
-      }
+      updatingResource.put(key, updatingResource.get(attr));
       if (finalParameter) {
         finalParameters.add(key);
       }
@@ -1581,9 +1565,7 @@ public class Configuration implements Iterable<Map.Entry<String,String>>,
           if (value != null) {
             if (!finalParameters.contains(attr)) {
               properties.setProperty(attr, value);
-              if (storeResource) {
-                updatingResource.put(attr, name.toString());
-              }
+              updatingResource.put(attr, name.toString());
             } else {
               LOG.warn(name+":a attempt to override final parameter: "+attr
                      +";  Ignoring.");
@@ -1611,12 +1593,22 @@ public class Configuration implements Iterable<Map.Entry<String,String>>,
   }
 
   /** 
-   * Write out the non-default properties in this configuration to the give
+   * Write out the non-default properties in this configuration to the given
    * {@link OutputStream}.
    * 
    * @param out the output stream to write to.
    */
   public void writeXml(OutputStream out) throws IOException {
+    writeXml(new OutputStreamWriter(out));
+  }
+
+  /** 
+   * Write out the non-default properties in this configuration to the given
+   * {@link Writer}.
+   * 
+   * @param out the writer to write to.
+   */
+  public synchronized void writeXml(Writer out) throws IOException {
     Properties properties = getProps();
     try {
       Document doc =
@@ -1635,7 +1627,12 @@ public class Configuration implements Iterable<Map.Entry<String,String>>,
         }
         Element propNode = doc.createElement("property");
         conf.appendChild(propNode);
-      
+
+        if (updatingResource != null) {
+          Comment commentNode = doc.createComment(
+            "Loaded from " + updatingResource.get(name));
+          propNode.appendChild(commentNode);
+        }
         Element nameNode = doc.createElement("name");
         nameNode.appendChild(doc.createTextNode(name));
         propNode.appendChild(nameNode);
@@ -1652,8 +1649,10 @@ public class Configuration implements Iterable<Map.Entry<String,String>>,
       TransformerFactory transFactory = TransformerFactory.newInstance();
       Transformer transformer = transFactory.newTransformer();
       transformer.transform(source, result);
-    } catch (Exception e) {
-      throw new RuntimeException(e);
+    } catch (TransformerException te) {
+      throw new IOException(te);
+    } catch (ParserConfigurationException pe) {
+      throw new IOException(pe);
     }
   }
 
@@ -1668,26 +1667,26 @@ public class Configuration implements Iterable<Map.Entry<String,String>>,
    * @param out the Writer to write to
    * @throws IOException
    */
-  public static void dumpConfiguration(Configuration conf, 
+  public static void dumpConfiguration(Configuration config,
       Writer out) throws IOException {
-    Configuration config = new Configuration(conf,true);
-    config.reloadConfiguration();
     JsonFactory dumpFactory = new JsonFactory();
     JsonGenerator dumpGenerator = dumpFactory.createJsonGenerator(out);
     dumpGenerator.writeStartObject();
     dumpGenerator.writeFieldName("properties");
     dumpGenerator.writeStartArray();
     dumpGenerator.flush();
-    for (Map.Entry<Object,Object> item: config.getProps().entrySet()) {
-      dumpGenerator.writeStartObject();
-      dumpGenerator.writeStringField("key", (String) item.getKey());
-      dumpGenerator.writeStringField("value", 
-          config.get((String) item.getKey()));
-      dumpGenerator.writeBooleanField("isFinal",
-          config.finalParameters.contains(item.getKey()));
-      dumpGenerator.writeStringField("resource",
-          config.updatingResource.get(item.getKey()));
-      dumpGenerator.writeEndObject();
+    synchronized (config) {
+      for (Map.Entry<Object,Object> item: config.getProps().entrySet()) {
+        dumpGenerator.writeStartObject();
+        dumpGenerator.writeStringField("key", (String) item.getKey());
+        dumpGenerator.writeStringField("value", 
+                                       config.get((String) item.getKey()));
+        dumpGenerator.writeBooleanField("isFinal",
+                                        config.finalParameters.contains(item.getKey()));
+        dumpGenerator.writeStringField("resource",
+                                       config.updatingResource.get(item.getKey()));
+        dumpGenerator.writeEndObject();
+      }
     }
     dumpGenerator.writeEndArray();
     dumpGenerator.writeEndObject();

src/java/org/apache/hadoop/http/HttpServer.java

@@ -46,6 +46,7 @@ import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.log.LogLevel;
 import org.apache.hadoop.metrics.MetricsServlet;
 import org.apache.hadoop.util.ReflectionUtils;
+import org.apache.hadoop.conf.ConfServlet;
 
 import org.mortbay.jetty.Connector;
 import org.mortbay.jetty.Handler;
@@ -77,6 +78,10 @@ public class HttpServer implements FilterContainer {
   static final String FILTER_INITIALIZER_PROPERTY
       = "hadoop.http.filter.initializers";
 
+  // The ServletContext attribute where the daemon Configuration
+  // gets stored.
+  public static final String CONF_CONTEXT_ATTRIBUTE = "hadoop.conf";
+
   protected final Server webServer;
   protected final Connector listener;
   protected final WebAppContext webAppContext;
@@ -122,6 +127,7 @@ public class HttpServer implements FilterContainer {
     webAppContext = new WebAppContext();
     webAppContext.setContextPath("/");
     webAppContext.setWar(appDir + "/" + name);
+    webAppContext.getServletContext().setAttribute(CONF_CONTEXT_ATTRIBUTE, conf);
     webServer.addHandler(webAppContext);
 
     addDefaultApps(contexts, appDir);
@@ -200,6 +206,7 @@ public class HttpServer implements FilterContainer {
     addServlet("stacks", "/stacks", StackServlet.class);
     addServlet("logLevel", "/logLevel", LogLevel.Servlet.class);
     addServlet("metrics", "/metrics", MetricsServlet.class);
+    addServlet("conf", "/conf", ConfServlet.class);
   }
 
   public void addContext(Context ctxt, boolean isFiltered)

src/test/core/org/apache/hadoop/conf/TestConfServlet.java

@@ -0,0 +1,111 @@
+/**
+ * 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 java.io.StringWriter;
+import java.io.StringReader;
+import java.util.Map;
+import javax.xml.parsers.DocumentBuilder;
+import javax.xml.parsers.DocumentBuilderFactory;
+
+import org.mortbay.util.ajax.JSON;
+import org.mortbay.util.ajax.JSON.Output;
+import org.w3c.dom.Document;
+import org.w3c.dom.Element;
+import org.w3c.dom.Node;
+import org.w3c.dom.NodeList;
+import org.xml.sax.InputSource;
+
+import junit.framework.TestCase;
+import org.junit.Test;
+
+/**
+ * Basic test case that the ConfServlet can write configuration
+ * to its output in XML and JSON format.
+ */
+public class TestConfServlet extends TestCase {
+  private static final String TEST_KEY = "testconfservlet.key";
+  private static final String TEST_VAL = "testval";
+
+  private Configuration getTestConf() {
+    Configuration testConf = new Configuration();
+    testConf.set(TEST_KEY, TEST_VAL);
+    return testConf;
+  }
+
+  @Test
+  @SuppressWarnings("unchecked")
+  public void testWriteJson() throws Exception {
+    StringWriter sw = new StringWriter();
+    ConfServlet.writeResponse(getTestConf(), sw, "json");
+    String json = sw.toString();
+    boolean foundSetting = false;
+    Object parsed = JSON.parse(json);
+    Object[] properties = ((Map<String, Object[]>)parsed).get("properties");
+    for (Object o : properties) {
+      Map<String, Object> propertyInfo = (Map<String, Object>)o;
+      String key = (String)propertyInfo.get("key");
+      String val = (String)propertyInfo.get("value");
+      String resource = (String)propertyInfo.get("resource");
+      System.err.println("k: " + key + " v: " + val + " r: " + resource);
+      if (TEST_KEY.equals(key) && TEST_VAL.equals(val)
+          && Configuration.UNKNOWN_RESOURCE.equals(resource)) {
+        foundSetting = true;
+      }
+    }
+    assertTrue(foundSetting);
+  }
+
+  @Test
+  public void testWriteXml() throws Exception {
+    StringWriter sw = new StringWriter();
+    ConfServlet.writeResponse(getTestConf(), sw, "xml");
+    String xml = sw.toString();
+
+    DocumentBuilderFactory docBuilderFactory 
+      = DocumentBuilderFactory.newInstance();
+    DocumentBuilder builder = docBuilderFactory.newDocumentBuilder();
+    Document doc = builder.parse(new InputSource(new StringReader(xml)));
+    NodeList nameNodes = doc.getElementsByTagName("name");
+    boolean foundSetting = false;
+    for (int i = 0; i < nameNodes.getLength(); i++) {
+      Node nameNode = nameNodes.item(i);
+      String key = nameNode.getTextContent();
+      System.err.println("xml key: " + key);
+      if (TEST_KEY.equals(key)) {
+        foundSetting = true;
+        Element propertyElem = (Element)nameNode.getParentNode();
+        String val = propertyElem.getElementsByTagName("value").item(0).getTextContent();
+        assertEquals(TEST_VAL, val);
+      }
+    }
+    assertTrue(foundSetting);
+  }
+
+  @Test
+  public void testBadFormat() throws Exception {
+    StringWriter sw = new StringWriter();
+    try {
+      ConfServlet.writeResponse(getTestConf(), sw, "not a format");
+      fail("writeResponse with bad format didn't throw!");
+    } catch (ConfServlet.BadFormatException bfe) {
+      // expected
+    }
+    assertEquals("", sw.toString());
+  }
+}