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CockroachDB国内俗称小强DB，是国外开发的一款兼容PostgreSQL协议的NewSQL数据库；据了解其研发团队均为 Google 的分布式文件系统 Colossus 团队的成员组成，从设计上来讲有点类似Google的Spanner分布式数据库( 全球第一款分布式数据库)。是否好用，这里不多说，先来简单尝试一下，从安装玩起。
1、软件下载略，直接解压cp到/usr/bin即可。
2、启动节点1
[root@mysqldb1 opt]# cockroach start --insecure --host=mysqldb1 --background --http-port=8081 * * WARNING: RUNNING IN INSECURE MODE! * * - Your cluster is open for any client that can access mysqldb1. * - Any user, even root, can log in without providing a password. * - Any user, connecting as root, can read or write any data in your cluster. * - There is no network encryption nor authentication, and thus no confidentiality. * * Check out how to secure your cluster: https://www.cockroachlabs.com/docs/v2.0/secure-a-cluster.html * [root@mysqldb1 opt]# CockroachDB node starting at 2018-05-14 03:33:31.306339131 +0000 UTC (took 0.7s) build: CCL v2.0.1 @ 2018/04/23 18:39:21 (go1.10) admin: http://mysqldb1:8081 sql: postgresql://root@mysqldb1:26257?sslmode=disable logs: /opt/cockroach-data/logs temp dir: /opt/cockroach-data/cockroach-temp623324603 external I/O path: /opt/cockroach-data/extern store[0]: path=/opt/cockroach-data status: restarted pre-existing node clusterID: 749ea85a-66ff-44eb-9161-f00873078136 nodeID: 1
从这里的启动输出信息来看，命令行的完全兼容了postgreSQL；启动之后每个节点会分配一个Nodeid和clusterID(每个集群的clusterid是唯一的)。
3、启动节点2、3
root@mysqldb2 opt]# cockroach start --insecure --store=node2 --host=mysqldb2 --http-port=8082 --join=172.16.29.154:26257 & [1] 42677 [root@mysqldb2 opt]# * * WARNING: RUNNING IN INSECURE MODE! * * - Your cluster is open for any client that can access mysqldb2. * - Any user, even root, can log in without providing a password. * - Any user, connecting as root, can read or write any data in your cluster. * - There is no network encryption nor authentication, and thus no confidentiality. * * Check out how to secure your cluster: https://www.cockroachlabs.com/docs/v2.0/secure-a-cluster.html * [root@mysqldb2 opt]# CockroachDB node starting at 2018-05-14 04:17:25.22193837 +0000 UTC (took 0.7s) build: CCL v2.0.1 @ 2018/04/23 18:39:21 (go1.10) admin: http://mysqldb2:8082 sql: postgresql://root@mysqldb2:26257?sslmode=disable logs: /opt/node2/logs temp dir: /opt/node2/cockroach-temp449846681 external I/O path: /opt/node2/extern store[0]: path=/opt/node2 status: restarted pre-existing node clusterID: 749ea85a-66ff-44eb-9161-f00873078136 nodeID: 2 [root@mysqldb3 opt]# cockroach start --insecure --store=node3 --host=mysqldb3 --http-port=8083 --join=172.16.29.154:26257 & [1] 53289
这里启动时可以直接挂后台运行，启动完毕之后，可以登录Url监控控制台进行查看。总的来讲整界面还是比较清爽的。
4、节点1创建测试表并插入测试数据
[root@mysqldb1 opt]# cockroach sql --url=postgresql://root@mysqldb1:26257?sslmode=disable # Welcome to the cockroach SQL interface. # All statements must be terminated by a semicolon. # To exit: CTRL + D. # # Server version: CockroachDB CCL v2.0.1 (x86_64-unknown-linux-gnu, built 2018/04/23 18:39:21, go1.10) (same version as client) # Cluster ID: 749ea85a-66ff-44eb-9161-f00873078136 # # Enter \? for a brief introduction. # warning: no current database set. Use SET database = <dbname> to change, CREATE DATABASE to make a new database. root@mysqldb1:26257/> root@mysqldb1:26257/> create database enmotech; CREATE DATABASE Time: 6.675781ms root@mysqldb1:26257/> set database=enmotech; SET Time: 357.175碌s root@mysqldb1:26257/enmotech> create table enmotech(id int,name varchar(20)); CREATE TABLE Time: 9.786659ms root@mysqldb1:26257/enmotech> insert into enmotech values(1,'www.enmotech.com'); INSERT 1 Time: 8.120407ms root@mysqldb1:26257/enmotech> insert into enmotech values(2,'www.killdb.com'); INSERT 1 Time: 24.219042ms
可以看到单条Insert的效率似乎并不高，这是为什么呢? 从原理上来讲，CockroachDB采用了share nothing架构，节点之间需要做同步，而且集群的性能也是受限于最差的那个节点，因此也存在木桶原理的问题。
至于如何保证节点之间的数据一致性，CockroachDB采用了raft协议，并没有使用Paxos。
5、在节点2、3验证数据
root@mysqldb2 opt]# cockroach sql --url=postgresql://root@mysqldb2:26257?sslmode=disable # Welcome to the cockroach SQL interface. # All statements must be terminated by a semicolon. # To exit: CTRL + D. # # Server version: CockroachDB CCL v2.0.1 (x86_64-unknown-linux-gnu, built 2018/04/23 18:39:21, go1.10) (same version as client) # Cluster ID: 749ea85a-66ff-44eb-9161-f00873078136 # # Enter \? for a brief introduction. # warning: no current database set. Use SET database = <dbname> to change, CREATE DATABASE to make a new database. root@mysqldb2:26257/> root@mysqldb2:26257/> set database=enmotech; SET Time: 1.200536ms root@mysqldb2:26257/enmotech> root@mysqldb2:26257/enmotech> select * from enmotech; +----+------------------+ | id | name | +----+------------------+ | 1 | www.enmotech.com | | 2 | www.killdb.com | +----+------------------+ (2 rows) Time: 5.247978ms root@mysqldb2:26257/enmotech> show create table enmotech; +----------+------------------------------------------+ | Table | CreateTable | +----------+------------------------------------------+ | enmotech | CREATE TABLE enmotech ( | | | | | | id INT NULL, | | | | | | "name" STRING(20) NULL, | | | | | | FAMILY "primary" (id, "name", rowid) | | | | | | ) | +----------+------------------------------------------+ (1 row) Time: 16.628783ms
我们可以发现数据已经完全同步到其他节点了。这里比较奇怪的是什么呢? 细心的朋友可能已经发现，该测试表我在创建的时候并没有指定主键，然而这里数据库确自动添加了主键。
前面提到了如何启动CockroachDB，那么如何停掉一个节点呢？命令其实非常的简单：
[root@mysqldb1 opt]# cockroach quit --host=172.16.29.154 --insecure --port=26257 ok [root@mysqldb1 opt]# [root@mysqldb3 tmp]# cockroach quit --host=172.16.29.133 --insecure --port=26257 ok [root@mysqldb3 tmp]#
最后我们来欣赏一下自带的监控界面:
