From 83fa9d80fa1fa2cc2d4fb7288a2fe46bfe2058f6 Mon Sep 17 00:00:00 2001
From: Mark Robert Miller <markrmiller@apache.org>
Date: Sun, 12 Feb 2012 02:45:06 +0000
Subject: [PATCH] SOLR-3125: When a SolrCore registers in zk there may be stale
 leader state in the clusterstate.json.

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1243195 13f79535-47bb-0310-9956-ffa450edef68
---
 .../org/apache/solr/cloud/ZkController.java   | 55 ++++++++++++++++---
 1 file changed, 48 insertions(+), 7 deletions(-)

diff --git a/solr/core/src/java/org/apache/solr/cloud/ZkController.java b/solr/core/src/java/org/apache/solr/cloud/ZkController.java
index b605abc4d8b..b6a1642e768 100644
--- a/solr/core/src/java/org/apache/solr/cloud/ZkController.java
+++ b/solr/core/src/java/org/apache/solr/cloud/ZkController.java
@@ -50,6 +50,7 @@ import org.apache.solr.core.SolrCore;
 import org.apache.solr.update.UpdateLog;
 import org.apache.zookeeper.CreateMode;
 import org.apache.zookeeper.KeeperException;
+import org.apache.zookeeper.KeeperException.NoNodeException;
 import org.apache.zookeeper.data.Stat;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -464,11 +465,6 @@ public final class ZkController {
     
     final CloudDescriptor cloudDesc = desc.getCloudDescriptor();
     final String collection = cloudDesc.getCollectionName();
-    
-
-    log.info("Attempting to update " + ZkStateReader.CLUSTER_STATE + " version "
-        + null);
-    CloudState state = CloudState.load(zkClient, zkStateReader.getCloudState().getLiveNodes());
 
     final String coreZkNodeName = getNodeName() + "_" + coreName;
     
@@ -495,8 +491,25 @@ public final class ZkController {
 
     joinElection(collection, coreZkNodeName, shardId, leaderProps);
     
-    String leaderUrl = zkStateReader.getLeaderUrl(collection,
-        cloudDesc.getShardId(), 30000);
+    // rather than look in the cluster state file, we go straight to the zknodes
+    // here, because on cluster restart there could be stale leader info in the
+    // cluster state node that won't be updated for a moment
+    String leaderUrl = getLeaderUrl(collection, cloudDesc.getShardId());
+    
+    // now wait until our currently cloud state contains the latest leader
+    String cloudStateLeader = zkStateReader.getLeaderUrl(collection, cloudDesc.getShardId(), 30000);
+    int tries = 0;
+    while (!leaderUrl.equals(cloudStateLeader)) {
+      if (tries == 60) {
+        throw new SolrException(ErrorCode.SERVER_ERROR,
+            "There is conflicting information about the leader of shard: "
+                + cloudDesc.getShardId());
+      }
+      Thread.sleep(1000);
+      tries++;
+      cloudStateLeader = zkStateReader.getLeaderUrl(collection,
+          cloudDesc.getShardId(), 30000);
+    }
     
     String ourUrl = ZkCoreNodeProps.getCoreUrl(baseUrl, coreName);
     log.info("We are " + ourUrl + " and leader is " + leaderUrl);
@@ -551,6 +564,32 @@ public final class ZkController {
 
     return shardId;
   }
+  
+  /**
+   * Get leader URL directly from zk nodes.
+   * 
+   * @param collection
+   * @param slice
+   * @return
+   * @throws KeeperException
+   * @throws InterruptedException
+   */
+  private String getLeaderUrl(final String collection, final String slice)
+      throws KeeperException, InterruptedException {
+    int iterCount = 60;
+    while (iterCount-- > 0)
+      try {
+        byte[] data = zkClient.getData(
+            ZkStateReader.getShardLeadersPath(collection, slice), null, null,
+            true);
+        ZkCoreNodeProps leaderProps = new ZkCoreNodeProps(
+            ZkNodeProps.load(data));
+        return leaderProps.getCoreUrl();
+      } catch (NoNodeException e) {
+        Thread.sleep(500);
+      }
+    throw new RuntimeException("Could not get leader props");
+  }
 
 
   private void joinElection(final String collection,
@@ -600,6 +639,8 @@ public final class ZkController {
         core.getUpdateHandler().getSolrCoreState().doRecovery(core);
         return true;
       }
+    } else {
+      log.info("I am the leader, no recovery necessary");
     }
     
     return false;