Memory Leak in Actix with Cockroachdb

A memory leak in an Actix web service that uses CockroachDB typically arises when application code creates database interactions that never release resources, or when result sets and prepared statement handles are retained beyond their needed lifetime. Because Actix is an asynchronous, actor-based framework, leaks often stem from state held in actors or futures that keep references to rows, connections, or large payloads longer than necessary. CockroachDB, as a distributed SQL database, can amplify these issues when queries return large pages of data, when transactions are not explicitly committed or rolled back, or when session or connection state is unintentionally preserved across requests.

In a black-box scan, middleBrick tests the unauthenticated attack surface and may observe indirect signs of resource pressure, such as degraded response times under repeated calls or elevated memory usage patterns correlated with specific endpoints. When an endpoint opens a CockroachDB connection or session, executes a query that streams rows, and fails to consume or drop the stream to release backend resources, the server-side cursor or prepared statement may remain active. With continuous traffic, these lingering resources accumulate, leading to increased memory consumption on the service and potentially on the database nodes. middleBrick runs 12 security checks in parallel and can surface related findings under Data Exposure and Unsafe Consumption when such patterns suggest data retention or handling anomalies.

Consider an Actix handler that repeatedly queries a CockroachDB table without closing rows or correctly awaiting transaction completion:

use actix_web::{web, HttpResponse, Result};
use cockroach_client::CockroachDb;

async fn list_items(db: web::Data) -> Result {
    let mut conn = db.get_conn().await?;
    let stream = conn.query("SELECT id, data FROM large_table WHERE status = $1", &[&"active"]).await?;
    // Missing: stream.try_next() consumption and proper drop/return
    Ok(HttpResponse::Ok().finish())
}

In this snippet, if the stream is not fully consumed or explicitly dropped, server-side resources associated with the query and any prepared statement may persist. Because Actix keeps the actor and its state alive until dropped, the handler’s captured db and any associated connection/session state can remain in memory. A continuous stream of requests can therefore manifest as a memory leak, with eventual impact on throughput and stability. The leak may also interact with transaction handling: starting a transaction with BEGIN but failing to issue COMMIT or ROLLBACK can leave temporary structures on the CockroachDB nodes, which the scanner may correlate with unusual storage or memory patterns.

middleBrick’s LLM/AI Security checks do not apply here, but its inventory and data exposure checks can help highlight endpoints with high data retrieval volumes or missing resource cleanup steps. Remediation focuses on ensuring every database interaction has a clear lifecycle: acquire, use, and release, with strict handling of rows, transactions, and prepared statements.

To fix memory leaks when using CockroachDB with Actix, ensure that all database cursors, rows, and transactions are deterministically released. Use Rust’s drop semantics and Actix’s async patterns to guarantee cleanup. Prefer short-lived connections and avoid storing large result sets in actor state.

Below are concrete, working code examples for Actix handlers that correctly manage resources against CockroachDB.

Example 1: Consume and drop rows explicitly within the handler

use actix_web::{web, HttpResponse, Result};
use cockroach_client::{CockroachDb, Row};
use futures::stream::TryStreamExt;

async fn list_items(db: web::Data) -> Result {
    let mut conn = db.get_conn().await?;
    let mut stream = conn.query("SELECT id, data FROM large_table WHERE status = $1", &[&"active"]).await?;
    let mut items = Vec::new();
    while let Some(row) = stream.try_next().await? {
        let id: i64 = row.get(0);
        let data: String = row.get(1);
        items.push((id, data));
    }
    // stream and connection go out of scope and are dropped here
    Ok(HttpResponse::Ok().json(items))
}

Example 2: Use a transaction with explicit commit/rollback and limited scope

use actix_web::{web, HttpResponse, Result};
use cockroach_client::{CockroachDb, Transaction};

async fn update_item(db: web::Data, item_id: web::Path) -> Result {
    let mut conn = db.get_conn().await?;
    let mut tx: Transaction<'_> = conn.transaction().await?;
    // Perform operations within the transaction
    tx.execute("UPDATE items SET processed = TRUE WHERE id = $1", &[&item_id]).await?;
    // Explicit commit ensures no open transaction resources linger
    tx.commit().await?;
    // If an error occurs, rollback is triggered before exiting the scope
    Ok(HttpResponse::Ok().finish())
}

Example 3: Reuse a connection pool and ensure streams are dropped promptly

use actix_web::{web, HttpResponse, Result};
use cockroach_client::Pool;

async fn safe_query(pool: web::Data) -> Result {
    let mut conn = pool.acquire().await?;
    let rows = conn.query("SELECT count(*) FROM events", &[]).await?;
    // Convert stream to a collection and drop the stream immediately
    let count: i64 = rows.try_fold(0i64, |acc, row| async move {
        let c: i64 = row.get(0);
        Ok(acc + c)
    }).await?;
    Ok(HttpResponse::Ok().body(format!("Total events: {}")))
}

In all examples, ensure that the CockroachDB client and Actix state do not retain references to rows or connections beyond the request scope. Configure connection pool limits appropriate to your workload to avoid resource exhaustion, and validate that long-running or streaming queries are paginated or bounded where feasible. middleBrick’s Pro plan supports continuous monitoring and can alert you if repeated scans indicate regressions tied to resource handling.