Neon postgres with pooled connection -ERROR r2d2: unnamed prepared statement does not exist

[dfberry]

I'm using R2D2 pools for an Axum web server and getting this error. At the time the error happens, no API calls have been made. The server has just started up. The pool manager is in state. Any help on how to resolve this or debug it to understand it better?

2025-02-12T21:58:09.950165Z ERROR r2d2: unnamed prepared statement does not exist    
2025-02-12T21:58:09.950180Z ERROR r2d2: unnamed prepared statement does not exist    
2025-02-12T21:58:09.986603Z ERROR r2d2: unnamed prepared statement does not exist    
2025-02-12T21:58:10.723594Z ERROR r2d2: unnamed prepared statement does not exist    
2025-02-12T21:58:10.726715Z ERROR r2d2: unnamed prepared statement does not exist    
2025-02-12T21:58:11.509051Z ERROR r2d2: unnamed prepared statement does not exist    
2025-02-12T21:58:11.616289Z ERROR r2d2: unnamed prepared statement does not exist    
2025-02-12T21:58:11.683564Z ERROR r2d2: unnamed prepared statement does not exist    
2025-02-12T21:58:12.443485Z ERROR r2d2: unnamed prepared statement does not exist    
2025-02-12T21:58:13.169553Z ERROR r2d2: unnamed prepared statement does not exist    
2025-02-12T21:58:13.277373Z ERROR r2d2: unnamed prepared statement does not exist    
2025-02-12T21:58:13.317765Z ERROR r2d2: unnamed prepared statement does not exist    
2025-02-12T21:58:14.069828Z ERROR r2d2: unnamed prepared statement does not exist    
2025-02-12T21:58:14.951186Z ERROR r2d2: unnamed prepared statement does not exist    
2025-02-12T21:58:15.709255Z ERROR r2d2: unnamed prepared statement does not exist 

My Cargo.toml is:

[dependencies]
anyhow = "1.0.86" 
axum = { version = "0.7.5", features = ["macros"] }
axum-extra = { version = "0.9.3", features = ["typed-header"] }
bson = "2.13.0"
chrono = "0.4.39"
diesel = { version = "2.2.3", features = ["postgres", "chrono", "r2d2"] }
futures = "0.3.31"
http = "1.1.0"
http-body-util = "0.1.0"
http-serde-ext = "1.0.2"
hyper = "1.0.0"
mongodb = "3.2.0"
octocrab = "0.41.0"
pq-sys = "0.6.1"
rand = "0.8"
regex = "1.11.1"
reqwest = { version = "0.12", features = ["json"] }
serde = { version = "1.0.217", features = ["derive"] }
serde_derive = "1.0.127"
serde_json = "1.0.137"
tokio = { version = "1.43.0", features = ["full"] }
toml = "0.8.19"
tower = "0.5.2"
tower-http = { version = "0.6.2", features = ["cors", "catch-panic", "sensitive-headers"] }
tracing = "0.1"
tracing-subscriber = "0.3"
url = "2.5.4"
urlencoding = "2.1.3"
uuid = { version = "1.12.1", features = ["v4","serde"] }

My pool connection looks like:

use diesel::pg::PgConnection;
use diesel::r2d2::{ConnectionManager, Pool, PooledConnection};
use std::env;
use tokio::task;
use std::sync::{Arc, RwLock};
use crate::state::{Config, AppState};

pub type PgPool = Pool<ConnectionManager<PgConnection>>;

// Called from config
pub async fn establish_connection_pool() -> PgPool {
    let database_url = env::var("DATABASE_URL").expect("DATABASE_URL must be set");

    if database_url.is_empty() {
        panic!("DATABASE_URL is empty. Please set a valid database URL.");
    }

    println!("Establishing connection pool to {}", database_url);

    task::spawn_blocking(move || {
        let manager = ConnectionManager::<PgConnection>::new(database_url);
        Pool::builder()
            .build(manager)
            .expect("Failed to create pool")
    })
    .await
    .expect("Pool creation task panicked")
}
// Called from each route
pub fn get_pg_client(state: &Arc<AppState>) -> PooledConnection<ConnectionManager<PgConnection>> {

    println!("Getting PG client");

    state
        .config
        .read()
        .unwrap()
        .pg
        .get()
        .expect("Failed to get DB connection")
}

[weiznich]

It's almost impossible to help with problems with proprietary postgresql offerings as I have no easy way to reproduce the problem on my own. Based on the error messages I would guess that there is some additional postgres connection pooling application in front of the actual postgres database and that pooling application doesn't support prepared statements as generated by diesel. That's something that's not supported by diesel.

[dfberry]

@weiznich I appreciate your response and knew it was a long shot so I kept plugging away at it. I have something that works in this commit. Not sure if it is the correct approach but it does seem to run.

[dfberry]

@weiznich What is the r2d2 package doing on starup or every 10 minutes? I'm getting this error from ORM when the app isn't getting any traffic.When the app actually makes a request through an Axum router to the db, I don't get that error.

[weiznich]

I fear that's again hard to answer without access to the environment where this kind of error occurs. I still believe that this might be what I wrote in my first response. You likely can verify that by contacting the neon support and ask them what's going on there. Otherwise I can really not add much here.

As a more general note: Please don't ping me to ask question, the next time I just won't response to such pings at all.