SolrCloud-如何在.NET程序中使用

https://github.com/vladen/SolrNet

原来我们在我们的项目里用的是根据数据库路由到不同的单机Solr服务器，但是这样的话，每次Solr配置的修改都要修改三台不通的服务器，而且一台服务器挂了，必定会影响一部分用户不能使用搜索功能，而且还会造成一定程度的丢数据，所以我们换一种方式。


经过对比，决定用SolrCloud，SolrCloud的概念和优缺点，就不再赘述了，网上一搜一大堆，这里主要写一下在C#如何使用SolrCloud。

最早我们用

EasyNet.Solr

来进行Solr查询的，但是貌似

EasyNet.Solr

没有对SolrCloud的查询做封装，所以就各种找资料，最后只能自己封装了。

首先SolrCloud是通过zookeeper来调度的，那么我们就要先去zookeeper上面去load可用的节点，并且对 zookeeper的 clusterstate.json 文件做心跳检测，如果clusterstate.json 里的内容有变化，则说明节点状态有变化，需要重新load文件里的内容进行解析，否则就在应用程序第一次调用的时候加载一次，缓存起来。

献上核心代码

要先通过NuGet安装Zookeeper Client

在

EasyNet.Solr

根目录定义接口

ISolrCloudOperrations.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace EasyNet.Solr
{
public interface ISolrCloudOperrations
{
string GetSolrCloudServer(string collectionName, bool isWrite);
}
}

在Impl文件夹里实现接口

SolrCloudOperations.cs

internal static class ZookeeperStatus
{
//每隔两秒钟pingzookeeper服务器，并监听solr服务器状态，如果状态有改变，更新状态文件，请求连接列表
private static void Ping(string zkHost) {
//如果是第一次调用，则加载配置文件
if (DataLength == 0)
{
foreach (var host in zkHost.Split(',').ToList())
{
Start(host);
}
Task.Factory.StartNew(() =>
{
while (true)
{
foreach (var host in zkHost.Split(',').ToList())
{
Task.Factory.StartNew(Start, host);
}
Thread.Sleep(2000);
}
});
}
}
private static object pingObj = new object();
private static void Start(object zkHost) {
var watcher = new Watcher();
using (var zk = new ZooKeeper(zkHost.ToString(), new TimeSpan(0, 0, 0, 10000), watcher))
{
var dataChange = watcher.WaitUntilWatched();
Org.Apache.Zookeeper.Data.Stat stat = null;
try
{
stat = zk.Exists("/clusterstate.json", false);
}
finally
{
if (stat != null)
{
byte[] data = null;
lock (pingObj)
{
if (DataLength == 0 || DataLength != stat.DataLength)
{
data = zk.GetData("/clusterstate.json", false, stat);
DataLength = stat.DataLength;
SetShard(data);
}
}
}
}
}
}

private static int DataLength = 0;

private static Dictionary<string, List<Shard>> shards = new Dictionary<string, System.Collections.Generic.List<Shard>>();
private static ReaderWriterLockSlim rw = new ReaderWriterLockSlim();
private static void SetShard(byte[] data)
{
var str = System.Text.Encoding.UTF8.GetString(data);
JObject jObj = JsonConvert.DeserializeObject<JObject>(str);
List<Shard> shardList = new List<Shard>();
try
{
rw.EnterWriteLock();
foreach (var p in jObj)
{
foreach (var item in p.Value["shards"])
{
var jItem = item.First as JObject;
if (jItem["state"].ToString() == "active")
{
foreach (var replica in jItem["replicas"])
{
var jReplica = replica.First as JObject;
if (jReplica["state"].ToString() == "active")
{
Shard shard = new Shard() { BaseUrl = jReplica["base_url"].ToString() };
if (jReplica["leader"] != null && "true" == jReplica["leader"].ToString())
{
shard.Leader = true;
}
shardList.Add(shard);
}
}
}
}
if (shards.ContainsKey(p.Key))
{
shards[p.Key] = shardList;
}
else
{
shards.Add(p.Key, shardList);
}
}
}
finally
{
rw.ExitWriteLock();
}
}

public static string ZookeeperHost = "127.0.0.1:2181";

public static string GetCollection(string collectionName, bool isWrite)
{
///第一次调用，则开始ping
if (DataLength == 0)
{
Ping(ZookeeperHost);
}
IEnumerable<Shard> tempShardList = null;
try
{
rw.EnterReadLock();
var shardList = shards[collectionName];

if (!isWrite)
{
tempShardList = shardList.Where(s => s.Leader == false);
}
//如果从库挂了，那么只能从主库读取了
if (tempShardList == null || tempShardList.Count() == 0)
tempShardList = shardList.Where(s => s.Leader == true);
}
finally
{
rw.ExitReadLock();
}
if (tempShardList == null) throw new Exception("no active shard");
//随机取值
int random = new Random().Next(tempShardList.Count() - 1);
return tempShardList.ToList()[random].BaseUrl;
}

}
internal class Shard
{
public string BaseUrl { get; set; }
public bool Leader { get; set; }
}
internal enum Changed
{
None,
Children,
Data
}
internal class Watcher : IWatcher
{
private readonly ManualResetEventSlim _changed = new ManualResetEventSlim(false);
private WatchedEvent _event;
public Changed WaitUntilWatched()
{
_changed.Wait();
if (_event == null) throw new ApplicationException("bad state");
if (_event.State != KeeperState.SyncConnected)
throw new ApplicationException("cannot connect");
if (_event.Type == EventType.NodeChildrenChanged)
{
return Changed.Children;
}
if (_event.Type == EventType.NodeDataChanged)
{
return Changed.Data;
}
return Changed.None;
}
void IWatcher.Process(WatchedEvent @event)
{
_event = @event;
_changed.Set();
}
}

这样我们如果是write操作，就会调用leader分片对应的节点进行写入，如果是查询操作，则尽量直接调用非leader来进行查询，如果非leader节点挂了，那么久从主节点进行查询。