Advice on protecting against connection churn DOS

[greg-blackcurrent]

Scenario:

Consider a web server using net/http which is connected to a database using pgxpool, and no pgbouncer etc.

If malicious or broken http clients, create a large number of connections, and close them after 10ms.

This can cause a large number of context cancellations. This will cause pgx to close the connections, and immediately reconnect.

Since database connections in postgres are quite heavyweight, this could cause a lot of load on the database.

Should I be concerned about this? How can I protect my application against it?

[greg-blackcurrent]

This documentation is helpful.

Context Support

All potentially blocking operations take a context.Context. The default behavior when a context is canceled is for the
method to immediately return. In most circumstances, this will also close the underlying connection. This behavior can
be customized by using BuildContextWatcherHandler on the Config to create a ctxwatch.Handler with different behavior.
This can be especially useful when queries that are frequently canceled and the overhead of creating new connections is
a problem. DeadlineContextWatcherHandler and CancelRequestContextWatcherHandler can be used to introduce a delay before
interrupting the query in such a way as to close the connection.

The CancelRequest method may be used to request the PostgreSQL server cancel an in-progress query without forcing the
client to abort.

[jackc]

You found the answer. You can configure context cancellation behavior to reduce or eliminate the chance of a connection being closed at the expense of the function executing when the context was cancelled not returning as quickly.