The supported routing methods, typical uses and use cases are listed in Table 6.1, “Routing Method Selection”.
Table 6.1. Routing Method Selection
|Routing Method||Host Selection||Auto R/W Splitting||Replica Latency||Maximum Applied Latency|
|Smartscale||By Session||Yes (by SQL statement)||Lazy||Yes|
|Direct Reads||By Content||Yes (by SQL statement)||Lazy||Yes|
|Port-based||By Network Port||No||No||Yes|
|SQL-based||By SQL comment||No||No||Yes|
Both SmartScale and R/W splitting cannot be enabled at the same time. This is because they are two sides of the basic functionality. R/W splitting and SmartScale both use SQL introspection to determine whether a query should be directed to a Primary or a Replica. SmartScale combines this with an intelligent load-balancer. R/W splitting uses a simpler direct redirection.
In addition to the selection and configuration mechanisms supported, a routing method should be chosen based on your application abilities:
If the application is replication-aware, and can already direct queries to Primary or Replicas based on the operation type, use Section 6.4.9, “Host-based Routing” or Section 6.4.10, “Port-based Routing”
If the application has full control of the SQL statements submitted (i.e. not through a third-party tool, or Object-Relational Modeling library), and can already direct queries to Primary or Replicas based on the operation type, use Section 6.4.8, “SQL Routing”.