Index: solr/core/src/test/org/apache/solr/core/TestSolrXmlPersistor.java
===================================================================
--- solr/core/src/test/org/apache/solr/core/TestSolrXmlPersistor.java	(revision 1514699)
+++ solr/core/src/test/org/apache/solr/core/TestSolrXmlPersistor.java	(working copy)
@@ -35,7 +35,7 @@
 
     final String solrxml = "<solr><cores adminHandler=\"/admin\"/></solr>";
 
-    SolrXMLCoresLocator persistor = new SolrXMLCoresLocator(new File("testfile.xml"), solrxml, null);
+    SolrXMLCoresLocator persistor = new SolrXMLCoresLocator(solrxml, null);
     assertEquals(persistor.buildSolrXML(EMPTY_CD_LIST),
         "<solr><cores adminHandler=\"/admin\"></cores></solr>");
 
@@ -45,7 +45,7 @@
   public void emptyCoresTagIsPersisted() {
     final String solrxml = "<solr><cores adminHandler=\"/admin\"></cores></solr>";
 
-    SolrXMLCoresLocator persistor = new SolrXMLCoresLocator(new File("testfile.xml"), solrxml, null);
+    SolrXMLCoresLocator persistor = new SolrXMLCoresLocator(solrxml, null);
     assertEquals(persistor.buildSolrXML(EMPTY_CD_LIST), "<solr><cores adminHandler=\"/admin\"></cores></solr>");
   }
 
@@ -53,7 +53,7 @@
   public void emptySolrXmlIsPersisted() {
     final String solrxml = "<solr></solr>";
 
-    SolrXMLCoresLocator persistor = new SolrXMLCoresLocator(new File("testfile.xml"), solrxml, null);
+    SolrXMLCoresLocator persistor = new SolrXMLCoresLocator(solrxml, null);
     assertEquals(persistor.buildSolrXML(EMPTY_CD_LIST), "<solr><cores></cores></solr>");
   }
 
@@ -68,7 +68,7 @@
     final CoreDescriptor cd = new CoreDescriptor(cc, "testcore", "instance/dir/");
     List<CoreDescriptor> cds = ImmutableList.of(cd);
 
-    SolrXMLCoresLocator persistor = new SolrXMLCoresLocator(new File("testfile.xml"), solrxml, null);
+    SolrXMLCoresLocator persistor = new SolrXMLCoresLocator(solrxml, null);
     assertEquals(persistor.buildSolrXML(cds),
           "<solr><cores>" + SolrXMLCoresLocator.NEWLINE
         + "    <core name=\"testcore\" instanceDir=\"instance/dir/\"/>" + SolrXMLCoresLocator.NEWLINE
@@ -89,7 +89,7 @@
           "</cores>" +
         "</solr>";
 
-    SolrXMLCoresLocator locator = new SolrXMLCoresLocator(new File("testfile.xml"), solrxml, null);
+    SolrXMLCoresLocator locator = new SolrXMLCoresLocator(solrxml, null);
     assertTrue(locator.getTemplate().contains("{{CORES_PLACEHOLDER}}"));
     assertTrue(locator.getTemplate().contains("<shardHandlerFactory "));
     assertTrue(locator.getTemplate().contains("${socketTimeout:500}"));
@@ -107,15 +107,14 @@
           "</cores>" +
         "</solr>";
 
-    SolrXMLCoresLocator locator = new SolrXMLCoresLocator(new File("testfile.xml"), solrxml, null);
+    SolrXMLCoresLocator locator = new SolrXMLCoresLocator(solrxml, null);
     assertTrue(locator.getTemplate().contains("{{CORES_PLACEHOLDER}}"));
     assertTrue(locator.getTemplate().contains("<shardHandlerFactory "));
   }
 
   @Test
   public void complexXmlIsParsed() {
-    SolrXMLCoresLocator locator = new SolrXMLCoresLocator(new File("testfile.xml"),
-                                        TestSolrXmlPersistence.SOLR_XML_LOTS_SYSVARS, null);
+    SolrXMLCoresLocator locator = new SolrXMLCoresLocator(TestSolrXmlPersistence.SOLR_XML_LOTS_SYSVARS, null);
     assertTrue(locator.getTemplate().contains("{{CORES_PLACEHOLDER}}"));
   }
 
Index: solr/core/src/test/org/apache/solr/core/TestLazyCores.java
===================================================================
--- solr/core/src/test/org/apache/solr/core/TestLazyCores.java	(revision 1514699)
+++ solr/core/src/test/org/apache/solr/core/TestLazyCores.java	(working copy)
@@ -69,7 +69,7 @@
     FileUtils.write(solrXml, LOTS_SOLR_XML, IOUtils.CHARSET_UTF_8.toString());
     ConfigSolrXmlOld config = (ConfigSolrXmlOld) ConfigSolr.fromFile(loader, solrXml);
 
-    CoresLocator locator = new SolrXMLCoresLocator.NonPersistingLocator(solrXml, LOTS_SOLR_XML, config);
+    CoresLocator locator = new SolrXMLCoresLocator.NonPersistingLocator(LOTS_SOLR_XML, config);
 
 
     final CoreContainer cores = new CoreContainer(loader, config, locator);
Index: solr/core/src/test/org/apache/solr/cloud/SolrXmlInZkTest.java
===================================================================
--- solr/core/src/test/org/apache/solr/cloud/SolrXmlInZkTest.java	(revision 0)
+++ solr/core/src/test/org/apache/solr/cloud/SolrXmlInZkTest.java	(revision 0)
@@ -0,0 +1,232 @@
+package org.apache.solr.cloud;
+/*
+ * 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.
+ */
+
+import com.carrotsearch.randomizedtesting.rules.SystemPropertiesRestoreRule;
+import org.apache.commons.io.FileUtils;
+import org.apache.solr.SolrTestCaseJ4;
+import org.apache.solr.common.SolrException;
+import org.apache.solr.common.cloud.SolrZkClient;
+import org.apache.solr.common.cloud.ZkStateReader;
+import org.apache.solr.core.ConfigSolr;
+import org.apache.solr.core.SolrResourceLoader;
+import org.apache.solr.servlet.SolrDispatchFilter;
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.RuleChain;
+import org.junit.rules.TestRule;
+
+import java.io.File;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+
+public class SolrXmlInZkTest extends SolrTestCaseJ4 {
+
+  @Rule
+  public TestRule solrTestRules = RuleChain.outerRule(new SystemPropertiesRestoreRule());
+
+  protected ZkTestServer zkServer;
+
+  protected String zkDir;
+
+  private SolrZkClient zkClient;
+
+  private ZkStateReader reader;
+
+  private static int PORT = 7000;
+
+  private ConfigSolr cfg;
+
+  @Before
+  public void beforeClass() {
+    System.setProperty("solr.solrxml.location", "zookeeper");
+  }
+
+  private void setUpZkAndDiskXml(boolean toZk, boolean leaveOnLocal) throws Exception {
+
+    createTempDir();
+    File solrHome = new File(dataDir, "home");
+    copyMinConf(new File(solrHome, "myCollect"));
+    if (leaveOnLocal) {
+      FileUtils.copyFile(new File(SolrTestCaseJ4.TEST_HOME(), "solr-stress-new.xml"), new File(solrHome, "solr.xml"));
+    }
+
+    System.setProperty("solr.solr.home", solrHome.getAbsolutePath());
+
+    ignoreException("No UpdateLog found - cannot sync");
+    ignoreException("No UpdateLog found - cannot recover");
+
+    System.setProperty("zkClientTimeout", "8000");
+
+    zkDir = dataDir.getAbsolutePath() + File.separator
+        + "zookeeper" + System.currentTimeMillis() + "/server1/data";
+    zkServer = new ZkTestServer(zkDir);
+    zkServer.run();
+    System.setProperty("zkHost", zkServer.getZkAddress());
+    AbstractZkTestCase.buildZooKeeper(zkServer.getZkHost(),
+        zkServer.getZkAddress(), "solrconfig.xml", "schema.xml");
+
+    zkClient = new SolrZkClient(zkServer.getZkAddress(), AbstractZkTestCase.TIMEOUT);
+
+    if (toZk) {
+      zkClient.makePath("solr.xml", XML_FOR_ZK.getBytes(), true);
+    }
+
+    zkClient.close();
+
+    log.info("####SETUP_START " + getTestName());
+
+    // set some system properties for use by tests
+    System.setProperty("solr.test.sys.prop1", "propone");
+    System.setProperty("solr.test.sys.prop2", "proptwo");
+
+    Method method = SolrDispatchFilter.class.getDeclaredMethod("loadConfigSolr", SolrResourceLoader.class);
+    method.setAccessible(true);
+
+    Object obj = method.invoke(new SolrDispatchFilter(), new SolrResourceLoader(null));
+    cfg = (ConfigSolr) obj;
+
+    log.info("####SETUP_END " + getTestName());
+  }
+
+  private void closeZK() throws Exception {
+    if (zkClient != null) {
+      zkClient.close();
+    }
+
+    if (reader != null) {
+      reader.close();
+    }
+    zkServer.shutdown();
+  }
+
+  @Test
+  public void testXmlOnBoth() throws Exception {
+    try {
+      setUpZkAndDiskXml(true, true);
+      assertEquals("Should have gotten a new port the xml file sent to ZK, overrides the copy on disk",
+          cfg.getZkHostPort(), "9045");
+    } finally {
+      closeZK();
+    }
+  }
+
+  @Test
+  public void testXmlInZkOnly() throws Exception {
+    try {
+      setUpZkAndDiskXml(true, false);
+      assertEquals("Should have gotten a new port the xml file sent to ZK",
+          cfg.getZkHostPort(), "9045");
+    } finally {
+      closeZK();
+    }
+  }
+
+  //nocommit, tests fail!
+  @Test
+  public void testNotInZkAndShouldBe() throws Exception {
+    try {
+      setUpZkAndDiskXml(false, true);
+      fail("Should have gotten an exception here!");
+    } catch (InvocationTargetException ite) {
+      SolrException se = (SolrException) ite.getTargetException();
+      assertEquals("Should have an exception here, file not in ZK.",
+          "Could not load solr.xml from zookeeper", se.getMessage());
+    } finally {
+      closeZK();
+    }
+  }
+
+  // TODO: Solr 5.0. when we remove the default solr.xml from configSolrXmlOld this should start failing.
+  @Test
+  public void testNotInZkOrOnDisk() throws Exception {
+    try {
+      System.clearProperty("solr.solrxml.location");
+      System.setProperty("hostPort", "8787");
+      setUpZkAndDiskXml(false, false); // solr.xml not on disk either
+      assertEquals("Should have gotten the default port from the hard-coded default solr.xml file via sys prop.",
+          cfg.getZkHostPort(), "8787");
+    } finally {
+      closeZK();
+    }
+  }
+
+  @Test
+  public void testOnDiskOnly() throws Exception {
+    try {
+      System.clearProperty("solr.solrxml.location");
+      setUpZkAndDiskXml(false, true);
+      assertEquals("Should have gotten the default port", cfg.getZkHostPort(), "8983");
+    } finally {
+      closeZK();
+    }
+  }
+
+  @Test
+  public void testBadSysProp() throws Exception {
+    try {
+      System.setProperty("solr.solrxml.location", "solrHomeDir");
+      setUpZkAndDiskXml(false, true);
+      fail("Should have thrown exception in SolrXmlInZkTest.testBadSysProp");
+    } catch (InvocationTargetException ite) {
+      SolrException se = (SolrException) ite.getTargetException();
+      assertEquals("Should have an exception in SolrXmlInZkTest.testBadSysProp, sysprop set to bogus value.",
+          se.getMessage(), "Bad solr.solrxml.location set: solrHomeDir - should be 'solrhome' or 'zookeeper'");
+    } finally {
+      closeZK();
+    }
+
+  }
+
+  //SolrDispatchFilter.protected static ConfigSolr loadConfigSolr(SolrResourceLoader loader) {
+  @Test
+  public void testZkHostDiscovery() throws ClassNotFoundException, NoSuchMethodException,
+      IllegalAccessException, InstantiationException, InvocationTargetException {
+
+    // Should see an error when zkHost is not defined but solr.solrxml.location is set to zookeeper.
+    System.clearProperty("zkHost");
+    try {
+      Method method = SolrDispatchFilter.class.getDeclaredMethod("loadConfigSolr", SolrResourceLoader.class);
+      method.setAccessible(true);
+      method.invoke(new SolrDispatchFilter(), new SolrResourceLoader(null));
+      fail("Should have thrown an exception");
+    } catch (InvocationTargetException ite) {
+      assertTrue("Should be catching a SolrException", ite.getTargetException() instanceof SolrException);
+      String cause = ((SolrException) ite.getTargetException()).getMessage();
+
+      assertEquals("Caught Solr exception", cause,
+          "Could not load solr.xml from zookeeper: zkHost system property not set");
+    }
+  }
+
+  // Just a random port, I'm not going to use it but just check that the Solr instance constructed from the XML
+  // file in ZK overrides the default port.
+  private final String XML_FOR_ZK =
+      "<solr>" +
+          "  <solrcloud>" +
+          "    <str name=\"host\">127.0.0.1</str>" +
+          "    <int name=\"hostPort\">9045</int>" +
+          "    <str name=\"hostContext\">${hostContext:solr}</str>" +
+          "  </solrcloud>" +
+          "  <shardHandlerFactory name=\"shardHandlerFactory\" class=\"HttpShardHandlerFactory\">" +
+          "    <int name=\"socketTimeout\">${socketTimeout:120000}</int>" +
+          "    <int name=\"connTimeout\">${connTimeout:15000}</int>" +
+          "  </shardHandlerFactory>" +
+          "</solr>";
+
+}
Index: solr/core/src/java/org/apache/solr/servlet/SolrDispatchFilter.java
===================================================================
--- solr/core/src/java/org/apache/solr/servlet/SolrDispatchFilter.java	(revision 1514699)
+++ solr/core/src/java/org/apache/solr/servlet/SolrDispatchFilter.java	(working copy)
@@ -18,12 +18,14 @@
 package org.apache.solr.servlet;
 
 import org.apache.commons.io.IOUtils;
+import org.apache.commons.lang.StringUtils;
 import org.apache.solr.common.SolrException;
 import org.apache.solr.common.SolrException.ErrorCode;
 import org.apache.solr.common.cloud.Aliases;
 import org.apache.solr.common.cloud.ClusterState;
 import org.apache.solr.common.cloud.Replica;
 import org.apache.solr.common.cloud.Slice;
+import org.apache.solr.common.cloud.SolrZkClient;
 import org.apache.solr.common.cloud.ZkCoreNodeProps;
 import org.apache.solr.common.cloud.ZkNodeProps;
 import org.apache.solr.common.cloud.ZkStateReader;
@@ -35,9 +37,11 @@
 import org.apache.solr.common.util.NamedList;
 import org.apache.solr.common.util.SimpleOrderedMap;
 import org.apache.solr.common.util.StrUtils;
+import org.apache.solr.core.ConfigSolr;
 import org.apache.solr.core.CoreContainer;
 import org.apache.solr.core.SolrConfig;
 import org.apache.solr.core.SolrCore;
+import org.apache.solr.core.SolrResourceLoader;
 import org.apache.solr.handler.ContentStreamHandlerBase;
 import org.apache.solr.request.SolrQueryRequest;
 import org.apache.solr.request.SolrQueryRequestBase;
@@ -60,6 +64,7 @@
 import javax.servlet.ServletResponse;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
+import java.io.ByteArrayInputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
@@ -131,12 +136,44 @@
     log.info("SolrDispatchFilter.init() done");
   }
 
+  private ConfigSolr loadConfigSolr(SolrResourceLoader loader) {
+
+    String solrxmlLocation = System.getProperty("solr.solrxml.location", "solrhome");
+
+    if (solrxmlLocation == null || "solrhome".equalsIgnoreCase(solrxmlLocation))
+      return ConfigSolr.fromSolrHome(loader, loader.getInstanceDir());
+
+    if ("zookeeper".equalsIgnoreCase(solrxmlLocation)) {
+      String zkHost = System.getProperty("zkHost");
+      log.info("Trying to read solr.xml from " + zkHost);
+      if (StringUtils.isEmpty(zkHost))
+        throw new SolrException(ErrorCode.SERVER_ERROR,
+            "Could not load solr.xml from zookeeper: zkHost system property not set");
+      SolrZkClient zkClient = new SolrZkClient(zkHost, 30000);
+      try {
+        if (!zkClient.exists("/solr.xml", true))
+          throw new SolrException(ErrorCode.SERVER_ERROR, "Could not load solr.xml from zookeeper: node not found");
+        byte[] data = zkClient.getData("/solr.xml", null, null, true);
+        return ConfigSolr.fromInputStream(loader, new ByteArrayInputStream(data));
+      } catch (Exception e) {
+        throw new SolrException(ErrorCode.SERVER_ERROR, "Could not load solr.xml from zookeeper", e);
+      } finally {
+        zkClient.close();
+      }
+    }
+
+    throw new SolrException(ErrorCode.SERVER_ERROR,
+        "Bad solr.solrxml.location set: " + solrxmlLocation + " - should be 'solrhome' or 'zookeeper'");
+  }
+
   /**
    * Override this to change CoreContainer initialization
    * @return a CoreContainer to hold this server's cores
    */
   protected CoreContainer createCoreContainer() {
-    CoreContainer cores = new CoreContainer();
+    SolrResourceLoader loader = new SolrResourceLoader(SolrResourceLoader.locateSolrHome());
+    ConfigSolr config = loadConfigSolr(loader);
+    CoreContainer cores = new CoreContainer(loader, config);
     cores.load();
     return cores;
   }
Index: solr/core/src/java/org/apache/solr/core/ConfigSolr.java
===================================================================
--- solr/core/src/java/org/apache/solr/core/ConfigSolr.java	(revision 1514699)
+++ solr/core/src/java/org/apache/solr/core/ConfigSolr.java	(working copy)
@@ -61,10 +61,7 @@
       else {
         inputStream = new FileInputStream(configFile);
       }
-      ByteArrayOutputStream baos = new ByteArrayOutputStream();
-      ByteStreams.copy(inputStream, baos);
-      String originalXml = IOUtils.toString(new ByteArrayInputStream(baos.toByteArray()), "UTF-8");
-      return fromInputStream(loader, new ByteArrayInputStream(baos.toByteArray()), configFile, originalXml);
+      return fromInputStream(loader, inputStream);
     }
     catch (Exception e) {
       throw new SolrException(SolrException.ErrorCode.SERVER_ERROR,
@@ -76,13 +73,17 @@
   }
 
   public static ConfigSolr fromString(String xml) {
-    return fromInputStream(null, new ByteArrayInputStream(xml.getBytes(Charsets.UTF_8)), null, xml);
+    return fromInputStream(null, new ByteArrayInputStream(xml.getBytes(Charsets.UTF_8)));
   }
 
-  public static ConfigSolr fromInputStream(SolrResourceLoader loader, InputStream is, File file, String originalXml) {
+  public static ConfigSolr fromInputStream(SolrResourceLoader loader, InputStream is) {
     try {
-      Config config = new Config(loader, null, new InputSource(is), null, false);
-      return fromConfig(config, file, originalXml);
+      ByteArrayOutputStream baos = new ByteArrayOutputStream();
+      ByteStreams.copy(is, baos);
+      String originalXml = IOUtils.toString(new ByteArrayInputStream(baos.toByteArray()), "UTF-8");
+      ByteArrayInputStream dup = new ByteArrayInputStream(baos.toByteArray());
+      Config config = new Config(loader, null, new InputSource(dup), null, false);
+      return fromConfig(config, originalXml);
     }
     catch (Exception e) {
       throw new SolrException(SolrException.ErrorCode.SERVER_ERROR, e);
@@ -93,9 +94,9 @@
     return fromFile(loader, new File(solrHome, SOLR_XML_FILE));
   }
 
-  public static ConfigSolr fromConfig(Config config, File file, String originalXml) {
+  public static ConfigSolr fromConfig(Config config, String originalXml) {
     boolean oldStyle = (config.getNode("solr/cores", false) != null);
-    return oldStyle ? new ConfigSolrXmlOld(config, file, originalXml)
+    return oldStyle ? new ConfigSolrXmlOld(config, originalXml)
                     : new ConfigSolrXml(config);
   }
   
Index: solr/core/src/java/org/apache/solr/core/SolrXMLCoresLocator.java
===================================================================
--- solr/core/src/java/org/apache/solr/core/SolrXMLCoresLocator.java	(revision 1514699)
+++ solr/core/src/java/org/apache/solr/core/SolrXMLCoresLocator.java	(working copy)
@@ -41,7 +41,6 @@
 
   private static final Logger logger = LoggerFactory.getLogger(SolrXMLCoresLocator.class);
 
-  private final File file;
   private final String solrXmlTemplate;
   private final ConfigSolrXmlOld cfg;
 
@@ -50,13 +49,11 @@
 
   /**
    * Create a new SolrXMLCoresLocator
-   * @param file          a File object representing the file to write out to
    * @param originalXML   the original content of the solr.xml file
    * @param cfg           the CoreContainer's config object
    */
-  public SolrXMLCoresLocator(File file, String originalXML, ConfigSolrXmlOld cfg) {
+  public SolrXMLCoresLocator(String originalXML, ConfigSolrXmlOld cfg) {
     this.solrXmlTemplate = buildTemplate(originalXML);
-    this.file = file;
     this.cfg = cfg;
   }
 
@@ -147,6 +144,7 @@
   }
 
   protected void doPersist(String xml) {
+    File file = new File(cfg.config.getResourceLoader().getInstanceDir(), ConfigSolr.SOLR_XML_FILE);
     try {
       Writer writer = new OutputStreamWriter(new FileOutputStream(file), Charsets.UTF_8);
       writer.write(xml);
@@ -204,8 +202,8 @@
 
   public static class NonPersistingLocator extends SolrXMLCoresLocator {
 
-    public NonPersistingLocator(File file, String originalXML, ConfigSolrXmlOld cfg) {
-      super(file, originalXML, cfg);
+    public NonPersistingLocator(String originalXML, ConfigSolrXmlOld cfg) {
+      super(originalXML, cfg);
       this.xml = originalXML;
     }
 
Index: solr/core/src/java/org/apache/solr/core/ConfigSolrXmlOld.java
===================================================================
--- solr/core/src/java/org/apache/solr/core/ConfigSolrXmlOld.java	(revision 1514699)
+++ solr/core/src/java/org/apache/solr/core/ConfigSolrXmlOld.java	(working copy)
@@ -55,15 +55,15 @@
     return "solr/cores/shardHandlerFactory";
   }
 
-  public ConfigSolrXmlOld(Config config, File configFile, String originalXML) {
+  public ConfigSolrXmlOld(Config config, String originalXML) {
     super(config);
     try {
       checkForIllegalConfig();
       fillPropMap();
       config.substituteProperties();
       initCoreList();
-      this.persistor = isPersistent() ? new SolrXMLCoresLocator(configFile, originalXML, this)
-                                      : new SolrXMLCoresLocator.NonPersistingLocator(configFile, originalXML, this);
+      this.persistor = isPersistent() ? new SolrXMLCoresLocator(originalXML, this)
+                                      : new SolrXMLCoresLocator.NonPersistingLocator(originalXML, this);
     }
     catch (IOException e) {
       throw new SolrException(SolrException.ErrorCode.SERVER_ERROR, e);