Multiple servers and failover

In the router configuration, it is possible to specify multiple servers for one shard. Then the router will distribute read-only queries among the replicas. However, in addition to the automatic routing, you also have the option to explicitly define the destination for a specific query by using the target-session-attr parameter within the query. See Routing hints for more information.

-- you could specify target-session-attrs anywhere in your query
SELECT pg_is_in_recovery(), id FROM tsa_test WHERE id = 22 /* target-session-attrs: read-write */;
NOTICE: send query to shard(s) : sh1
 pg_is_in_recovery | id 
-------------------+----
 f                 | 22
(1 row)

Availability zone preferences

SPQR can prefer hosts in the router’s availability zone and fall back to other zones when no suitable local host is available. See Availability Zone Settings for configuration details and an example.

​Availability zone preferences

Availability zone preferences