ApsaraDB provides all of the data link services, including DNS, SLB, and Proxy. Because RDS uses the NativeDB Engine, and database operations are highly similar across engines, no learning cost is generated for users who are familiar with these data link services.
The DNS module supports the dynamic resolution of domain names to IP addresses, to prevent IP address changes from affecting the performance of RDS instances. After its domain name is configured in the connection pool, an ApsaraDB instance continues to be accessed even if the corresponding IP address changes.
For example, the domain name of an ApsaraDB instance is test.rds.aliyun.com, and the IP address corresponding to this domain name is 10.10.10.1. If either test.rds.aliyun.com or 10.10.10.1 is configured in the connection pool of a program, the instance can be accessed. After performing a zone migration or version upgrade for this ApsaraDB instance, the IP address may change to 10.10.10.2. If the domain name configured in the connection pool is test.rds.aliyun.com, the instance can still be accessed. However, if the IP address configured in the connection pool is 10.10.10.1, the instance is no longer accessible.
The SLB module provides instance IP addresses (including both intranet and Internet IP addresses) to prevent physical server changes from affecting the performance of RDS instances.
For example, the intranet IP address of an RDS instance is 10.1.1.1, and the corresponding Proxy or DB Engine runs on 192.168.0.1. Normally, the SLB module redirects all traffic destined for 10.1.1.1 to 192.168.0.1. If 192.168.0.1 fails, another address in hot standby status, 192.168.0.2, takes over for 192.168.0.1. In this case, the SLB module redirects all traffic destined for 10.1.1.1 to 192.168.0.2, and the RDS instance continues to offer its services normally.
The Proxy module performs a number of functions including data routing, traffic detection, and session holding.
Data routing: This supports distributed complex query aggregation for big data and provides the corresponding capacity management.
Traffic detection: This reduces SQL injection risks and supports SQL log backtracking when necessary.
Session holding: This prevents database connection interruptions if any failure occurs.
RDS fully supports mainstream database protocols, as shown in the following table:
|MySQL||5.1 (Deprecated), 5.5, 5.6, 5.7|
|SQL Server||2008 R2, 2012, 2016|
|PPAS||9.3, highly compatible with Oracle|