在同一请求期间使用 HikariCP 获取后续连接似乎很慢

Question

I have a Spring boot app that use HikariCP for Postgres connection pooling.

Recently I've set up tracing to collect some data how time is spent when handling a request to a specific endpoint.

My assumptions are that when using HikariCP:

1. The first connection to the database while handling the request might be a bit slower
2. Subsequent connections to the database should be fast (< 10 ms)

However, as the trace shows, the first connection is fast (< 10 ms). And while some subsequent connections during the same request handling are also fast (< 10 ms), I frequently see some subsequent connections taking 50-100ms, which seems quite slow to me, although I'm not sure if this is to be expected or not.

Is there anything I can configure to improve this behavior?

Maybe good to know:

• The backend in question doesn't really see any other traffic right now, so it's only handling traffic when I manually send requests to it
• I've changed maximumPoolSize to 1 to rule out that the issue is that it uses different connections in the context of 1 request and that's what causes the issue. The same behavior is still seen.

I use the default Hikari settings, I don't change them.

Answer 1

I do think something is wrong with your pool configuration or your usage of the pool if it takes roughly 10 ms to get an already initialized connection from your pool. I would expect it to be sub-millisecond... Are you sure you are using the pool correctly?

Make sure you are using as new versions of pool and driver as possible, and make sure that connectionTestQuery is not set, as that would execute a query every time the connection is obtained from the pool. The defaults should be good enough for the rest of the settings.

Debug logs could be one thing help figure out what is happening, metrics on the pool another. Have a look at Spring Boot Actuator, it will help you with that...

To answer your actual question on how you can improve the situation given it actually takes roughly 10 ms to obtain a connection: Do not obtain and return the connection to the pool for every query... If you do not want to pass the connection around in your code, and if it suits your use case, you can make this happen easily by making sure your whole request is wrapped in a transaction. See the Spring guide on managing transactions .