can someone point me to the documentation for java connection pooling with pinot?

Do you mean making concurrent requests to Pinot? If not, could you elaborate what you are looking for?

We don't want the connection to Pinot to be dropped and restarted for each query. In JDBC, you need a connection pooler. Does Pinot take care of that issue inside its client then?

We do not have connection pooling for client-side HTTP requests. The JDBC client sends HTTP requests to the available broker, which means each request blocks on a different thread, as you would expect. The thread executor for the client does not have a maximum amount of threads.

We're not experiencing any problems. I just wanted to understand how to minimize HTTP connection setup overhead. If Pinot is using JDBC, maybe something like c3p0 could keep a pool of open connections? This really has nothing to do with transactions or threads. All that's being pooled are a set of HTTP connections (to a broker). This optimization is really only useful because establishing new HTTP connections is expensive and there's no reason not to reuse old ones that are already opened. To make a query, a connection is retrieved from the pool, the request/response cycle occurs and the connection is returned to the pool. After a period of not being used, connections in the pool may be closed and removed from the pool.

The pinot client currently doesn’t do that (mostly because we haven’t experienced any issues). If you can open a GH issue, we can follow up

with large numbers of queries, HTTP setup overhead can be a substantial effect on latency. I will open an issue to record our discussion.

Thanks @User

This might be possible to implement using Keep-Alive HTTP header. Let me look into it.

I had done a POC with a netty based client, keeping a pool of client -> broker active keep-alive HTTP channels, such that we don't need to open a new one for each query. https://github.com/saurabhd336/pinot/pull/3/files If the community feels the need of such a client, I can pick this up and build on top of my changes.