Making pool connection cycling async

• asyncpg version: 0.14
• PostgreSQL version: 9.5/9.6
• Do you use a PostgreSQL SaaS? If so, which? Can you reproduce
  the issue with a local PostgreSQL install?: AWS RDS
• Python version: 3.6
• Platform: linux in docker
• Do you use pgbouncer?: Not in this instances
• Did you install asyncpg with pip?: yes
• If you built asyncpg locally, which version of Cython did you use?:
• Can the issue be reproduced under both asyncio and
  uvloop?: We only use asyncio

We have some application containers that use asyncpg connection pools, every now and again my performance tracing on our application request handlers shows that the connect method in the Pool takes a significant amount of time (sometimes 150ms) when establishing a connection to our RDS postgres instance (same Region).

The Pool has options to control how often a connection is pro-actively cycled, but my concern is that this results in clients of the pool having to wait for a connection to be established - I would much rather push this into a background async task who's job it is to take connections in/out of service so that inbound http requests to our server never incur the latency of performing the connection themselves.

Is this already doable or would it require some changes to asyncpg?

Bắt đầu bằng cách đọc entry point Pool.connect và các tùy chọn pool hiện có để chủ động luân phiên các kết nối. Theo dõi thời điểm việc thiết lập kết nối xảy ra đối với các request đến và xác định những thay đổi cần thiết cho việc luân phiên trong background; được xem là hoàn tất khi các client của pool không còn phải chịu độ trễ thiết lập kết nối đó.