MySQL vs. MongoDB: How to make decisions regarding high availability?

MySQL vs. MongoDB: How to make decisions about high availability?

Introduction: In today's Internet era, the demand for databases for large-scale applications is increasing. MySQL and MongoDB are two widely used database systems that offer different solutions in terms of high availability. This article will analyze the high availability features of MySQL and MongoDB and give corresponding decisions and examples.

1. High-availability features and decisions of MySQL

MySQL is a relational database management system with mature high-availability solutions. The following are several commonly used high availability features and decisions:

1. Master-Slave Replication: By replicating the master database (Master) to one or more slave databases (Slave). Realize redundant backup of data and separation of reading and writing. When the primary database fails, the secondary database can take over read and write requests.

Sample code (assuming there are 1 master server and 2 slave servers):

主服务器配置：
[mysqld]
server-id=1
log-bin=mysql-bin
binlog-format=ROW

从服务器配置：
[mysqld]
server-id=2
read-only=1
relay-log=mysql-relay-bin
log-slave-updates=1

2. Master-Master Replication: By combining multiple databases The server is set up as the main server to realize mutual backup of data and separation of reading and writing. Data consistency is maintained between master servers through replication.

Sample code (assuming 2 master servers):

主服务器1配置：
[mysqld]
server-id=1
log-bin=mysql-bin
binlog-format=ROW

主服务器2配置：
[mysqld]
server-id=2
log-bin=mysql-bin
binlog-format=ROW

3. MySQL Cluster: This is a solution for implementing a database cluster that can be deployed between multiple nodes. Distribute data and request load among them, improving availability and performance.

Sample code (assuming 3 nodes):

配置文件my.cnf：
[mysqld]
ndbcluster
ndb-connectstring=node1,node2,node3

启动集群：
$ ndbd
$ ndb_mgmd
$ mysqld

2. High availability features and decisions of MongoDB

MongoDB is a NoSQL database system that provides Various high-availability features. The following are several commonly used features and decisions:

1. Replica Set: Multiple MongoDB instances are formed into a cluster, with one instance being the master node (Primary) and the remaining instances being slave nodes. (Secondary). The master node handles all write operations, and the slave node is responsible for data synchronization and read operations. When the master node fails, one of the slave nodes will be elected as the new master node.

Sample code (assuming 3 nodes):

配置文件mongod.conf：
replication:
   replSetName: "rs0"

启动集群：
$ mongod --replSet rs0

2. Sharded Cluster: spread data across multiple MongoDB instances (shards) , to improve availability and performance. Each shard can be a replica set, consisting of multiple instances.

Sample code (assuming there are 3 shards, each shard consists of 3 nodes):

路由节点配置文件mongos.conf：
sharding:
   clusterRole: "configsvr"

启动路由节点：
$ mongos --configdb configReplSet/...

分片节点配置文件mongod.conf：
sharding:
   clusterRole: "shardsvr"

启动分片节点：
$ mongod --shardsvr

3. Automatic Failover: When MongoDB When a node fails, other nodes will automatically take over its functions to ensure high availability of services.

The above are just some of the major features and decisions regarding high availability for MySQL and MongoDB. In practical applications, factors such as fault detection, fault recovery, monitoring and backup also need to be considered. Different application scenarios may require different decisions and configurations.

Summary:

In terms of high availability, both MySQL and MongoDB provide a variety of solutions. Choosing the appropriate option requires trade-offs based on application needs, expected availability and performance, data consistency, and more. This article gives some sample code, hoping to help readers better understand and apply the high availability features of MySQL and MongoDB.

References:

1. MySQL official documentation: https://dev.mysql.com/doc/
2. MongoDB official documentation: https://docs. mongodb.com/

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