Rust and PostgreSQL troubleshooting
A request is stuck, a write returns an error, or memory keeps growing. Start with the question closest to what you see. Each guide follows a small reproduction and explains what its result can tell you.
Is my Rust request waiting for a connection or for PostgreSQL?
A Rust request is slow but its SQL is fast. A SQLx pool is full while PostgreSQL sessions look idle.
Keep in mind: An acquisition timeout can include connection creation and health checks. It does not prove that all slots were borrowed.
Does a Rust timeout prove that PostgreSQL stopped the query?
A write times out and the caller wants to retry. A dropped query future may have left work running on the server. Another request inherits a PostgreSQL statement limit after a pooled connection is returned.
Keep in mind: The reproduction deliberately retains the connection. It does not close the socket or test a proxy disconnect policy.
Does a bounded channel also bound the memory held by database producers?
A bounded Tokio queue stays small while the process retains large database results. Several tasks fetch their data before there is room to send it.
Keep in mind: The counter bounds logical application payload, not RSS, allocator capacity, SQLx buffers, or PostgreSQL memory.
Can I retry a write after losing PostgreSQL's commit reply?
The connection fails during commit and the caller cannot tell whether the write happened. An agent may retry the same approved action.
Keep in mind: The receipt covers a change in one PostgreSQL database. It does not make an email or an external payment atomic.
Why does a slow download keep other requests waiting for a database connection?
A Rust export starts quickly, then other requests queue when the client stops reading. Moving the producer into a background task did not free the connection.
Keep in mind: Fetching pages in separate transactions does not give one consistent snapshot of changing data. The test generates fixed records.
What should I check before giving an agent a read-only PostgreSQL tool?
An agent needs to read a customer's invoices through a Rust tool. The handler limits rows, but identity, query time, and returned text still need separate checks.
Keep in mind: The fixture tests the Rust database function. It does not implement an MCP transport, an authentication service, or a live model.
For other symptoms, try the Rust Failure Atlas. You can also explore the Rust reading paths.