ClickHouse之集群搭建以及数据复制

前面的文章简单的介绍了ClickHouse，以及也进行了简单的性能测试。本次说说集群的搭建以及数据复制，若是复制数据须要zookeeper配合。

环境：

1. 3台机器，我这里是3台虚拟机。都安装了clickhouse。

2. 绑定hosts，其实不绑定也不要紧，配置文件里面直接写ip。（3台机器都绑定hosts，以下）

192.168.0.10 db_server_yayun_01
192.168.0.20 db_server_yayun_02
192.168.0.30 db_server_yayun_03

3. 建立配置文件，默认这个配置文件是不存在的。/etc/clickhouse-server/config.xml有提示，以下：
If element has 'incl' attribute, then for it's value will be used corresponding substitution from another file.
By default, path to file with substitutions is /etc/metrika.xml. It could be changed in config in 'include_from' element.
Values for substitutions are specified in /yandex/name_of_substitution elements in that file.

配置文件/etc/metrika.xml内容以下：

<yandex>
<clickhouse_remote_servers>
    <perftest_3shards_1replicas>
        <shard>
             <internal_replication>true</internal_replication>
            <replica>
                <host>db_server_yayun_01</host>
                <port>9000</port>
            </replica>
        </shard>
        <shard>
            <replica>
                <internal_replication>true</internal_replication>
                <host>db_server_yayun_02</host>
                <port>9000</port>
            </replica>
        </shard>
        <shard>
            <internal_replication>true</internal_replication>
            <replica>
                <host>db_server_yayun_03</host>
                <port>9000</port>
            </replica>
        </shard>
    </perftest_3shards_1replicas>
</clickhouse_remote_servers>


<zookeeper-servers>
  <node index="1">
    <host>192.168.0.30</host>
    <port>2181</port>
  </node>
</zookeeper-servers>

<macros>
    <replica>192.168.0.10</replica>
</macros>


<networks>
   <ip>::/0</ip>
</networks>


<clickhouse_compression>
<case>
  <min_part_size>10000000000</min_part_size>             
  <min_part_size_ratio>0.01</min_part_size_ratio>
  <method>lz4</method>
</case>
</clickhouse_compression>

</yandex>

3台机器的配置文件都同样，惟一有区别的是：

<macros>
    <replica>192.168.0.10</replica>
</macros>

服务器ip是多少这里就写多少，其实不写ip也不要紧，3台机器不重复就行。这里是复制须要用到的配置。还有zk的配置以下：

<zookeeper-servers>
  <node index="1">
    <host>192.168.0.30</host>
    <port>2181</port>
  </node>
</zookeeper-servers>

个人zk是安装在30的机器上面的，只安装了一个实例，生产环境确定要放到单独的机器，而且配置成集群。配置文件修改好之后3台服务器重启。
官方文档给的步骤是：

ClickHouse deployment to cluster

ClickHouse cluster is a homogenous cluster. Steps to set up:

1. Install ClickHouse server on all machines of the cluster
2. Set up cluster configs in configuration file
3. Create local tables on each instance
4. Create a Distributed table

前面2步都搞定了，下面建立本地表，再建立Distributed表。（3台机器都建立，DDL不一样步，蛋疼）

CREATE TABLE ontime_local (FlightDate Date,Year UInt16) ENGINE = MergeTree(FlightDate, (Year, FlightDate), 8192);
CREATE TABLE ontime_all AS ontime_local ENGINE = Distributed(perftest_3shards_1replicas, default, ontime_local, rand())

插入数据（随便一台机器就行）：

:) insert into ontime_all (FlightDate,Year)values('2001-10-12',2001);

INSERT INTO ontime_all (FlightDate, Year) VALUES

Ok.

1 rows in set. Elapsed: 0.013 sec. 

:) insert into ontime_all (FlightDate,Year)values('2002-10-12',2002);

INSERT INTO ontime_all (FlightDate, Year) VALUES

Ok.

1 rows in set. Elapsed: 0.004 sec. 

:) insert into ontime_all (FlightDate,Year)values('2003-10-12',2003);

INSERT INTO ontime_all (FlightDate, Year) VALUES

Ok.

我这里插入了3条数据。下面查询看看（任何一台机器均可以）：

:) select * from  ontime_all;

SELECT *
FROM ontime_all 

┌─FlightDate─┬─Year─┐
│ 2001-10-12 │ 2001 │
└────────────┴──────┘
┌─FlightDate─┬─Year─┐
│ 2002-10-12 │ 2002 │
└────────────┴──────┘
┌─FlightDate─┬─Year─┐
│ 2003-10-12 │ 2003 │
└────────────┴──────┘
→ Progress: 3.00 rows, 12.00 B (48.27 rows/s., 193.08 B/s.) 
3 rows in set. Elapsed: 0.063 sec. 

:) 

当在其中一台机器上面查询的时候，抓包其余机器能够看见是有请求的。

tcpdump -i any -s 0 -l -w - dst port 9000

那么关闭其中一台机器呢？

:) select * from ontime_all;

SELECT *
FROM ontime_all 

┌─FlightDate─┬─Year─┐
│ 2001-10-12 │ 2001 │
└────────────┴──────┘
┌─FlightDate─┬─Year─┐
│ 2002-10-12 │ 2002 │
└────────────┴──────┘
┌─FlightDate─┬─Year─┐
│ 2003-10-12 │ 2003 │
└────────────┴──────┘
↓ Progress: 6.00 rows, 24.00 B (292.80 rows/s., 1.17 KB/s.) Received exception from server:
Code: 279. DB::Exception: Received from localhost:9000, ::1. DB::NetException. DB::NetException: All connection tries failed. Log: 

Code: 210, e.displayText() = DB::NetException: Connection refused: (db_server_yayun_02:9000, 192.168.0.20), e.what() = DB::NetException
Code: 210, e.displayText() = DB::NetException: Connection refused: (db_server_yayun_02:9000, 192.168.0.20), e.what() = DB::NetException
Code: 210, e.displayText() = DB::NetException: Connection refused: (db_server_yayun_02:9000, 192.168.0.20), e.what() = DB::NetException

能够看见已经抛错了，居然不是高可用？后面又看到了文档的另一种配置方法，那就是配置2个节点，副本2个，通过测试高可用没有问题，另外也是分布式并行查询。感兴趣的同窗能够自行测试。
https://clickhouse.yandex/reference_en.html#Distributed

下面进行数据复制的测试,zk已经配置好了，直接建表测试（3台机器都建立）：

CREATE TABLE ontime_replica (FlightDate Date,Year UInt16) ENGINE = ReplicatedMergeTree('/clickhouse_perftest/tables/ontime_replica','{replica}',FlightDate,(Year, FlightDate),8192);

插入数据测试：

insert into ontime_replica (FlightDate,Year)values('2018-10-12',2018);

任何一台机器都可查询到。其实到如今对于集群和复制都还没完全搞明白，由于分布式表也进行了数据复制，因此有点懵。有大婶的话欢迎一块儿交流。

 

参考资料：

https://clickhouse.yandex/reference_en.html#Distributed

https://clickhouse.yandex/tutorial.html