Single container start for whole integration test file

[Tockra]

Hello,

I'm writing integration tests in Rust, where I want to test the HTTP endpoints of my application. For this purpose, I need to mock the Keycloak login server, as I did not build a test mode into my application. To achieve this, I decided to start a real Keycloak server for my integration tests to ensure everything works as expected. The same I did for the database.

To do this, I need to start a Docker container with a specific image and run some setup scripts. However, starting a Docker container for each test is time-consuming, specially the keycloak auth container needs 10 seconds to receive connections, so I want to start a single auth container for all tests in a file. So 10 test methods needs only to wait one time for keycloak and not 10 times (10 x 10 seconds = 100 seconds test execution).

Previously, I found a solution that worked for a long time but now does not:

use ctor::{ctor, dtor};
use lazy_static::lazy_static;
use log::debug;
use mongodb::{
    bson::{doc, oid::ObjectId},
    options::{ClientOptions, UpdateModifications},
    Client, Collection,
};
use serde::Serialize;
use std::{env, thread};
use testcontainers::runners::AsyncRunner;
use testcontainers::{core::Mount, ContainerRequest, GenericImage, ImageExt};
use tokio::sync::Notify;

use common::{channel, execute_blocking, Channel, ContainerCommands};
#[path = "../common/mod.rs"]
pub mod common;

lazy_static! {
    static ref MONGODB_IN: Channel<ContainerCommands> = channel();
    static ref MONGODB_CONNECTION_STRING: Channel<String> = channel();
    static ref RUN_FINISHED: Notify = Notify::new();
}

#[ctor]
fn on_startup() {
    thread::spawn(|| {
        execute_blocking(start_mongodb());
        // This needs to be here otherwise the MongoDB container did not call the drop function before the application stops
        RUN_FINISHED.notify_one();
    });
}

#[dtor]
fn on_shutdown() {
    execute_blocking(clean_up());
}

async fn clean_up() {
    MONGODB_IN.tx.send(ContainerCommands::Stop).unwrap();

    // Wait until Docker is successfully stopped
    RUN_FINISHED.notified().await;
    debug!("MongoDB stopped.")
}

async fn start_mongodb() {
    let mongodb = get_mongodb_image().start().await.unwrap();
    let port = mongodb.get_host_port_ipv4(27017).await.unwrap();
    debug!("MongoDB started on port {}", port);
    let mut rx = MONGODB_IN.rx.lock().await;
    while let Some(command) = rx.recv().await {
        debug!("Received container command: {:?}", command);
        match command {
            ContainerCommands::FetchConnectionString => MONGODB_CONNECTION_STRING
                .tx
                .send(format!("mongodb://localhost:{}", port))
                .unwrap(),
            ContainerCommands::Stop => {
                mongodb.stop().await.unwrap();
                rx.close();
            }
        }
    }
}

fn get_mongodb_image() -> ContainerRequest<GenericImage> {
    let mount = Mount::bind_mount(
        format!(
            "{}/../../../../tests/docker-setup/mongo-init.js",
            get_current_absolute_path()
        ),
        "/docker-entrypoint-initdb.d/mongo-init.js",
    );
    GenericImage::new("mongo", "7.0.7")
        .with_cmd(["mongod", "--replSet", "rs0", "--bind_ip", "0.0.0.0"])
        .with_mount(mount)
}

fn get_current_absolute_path() -> String {
    match env::current_exe() {
        Ok(path) => {
            let path_str = path.to_string_lossy().into_owned();
            path_str
        }
        Err(_) => "/".to_string(),
    }
}

pub async fn get_mongodb_connection_string() -> String {
    MONGODB_IN
        .tx
        .send(ContainerCommands::FetchConnectionString)
        .unwrap();
    MONGODB_CONNECTION_STRING
        .rx
        .lock()
        .await
        .recv()
        .await
        .unwrap()
}

This code is placed in the db_container module. When I use mod db_container in my integration test files, it sets up and starts the container for all tests in the current file. Using get_mongodb_connection_string(), I can get the connection string to feed into my application.

However, I now receive this error on dtor:

thread '<unnamed>' panicked at library/std/src/thread/mod.rs:741:19:
use of std::thread::current() is not possible after the thread's local data has been destroyed
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
fatal runtime error: failed to initiate panic, error 5

The problem appears to be the clean_up() function, which causes this error even when its content is empty.

I'm reaching out to see if anyone using the testcontainers crate has a smart solution for this issue. Any insights or alternative approaches would be greatly appreciated!

Thank you!

[DDtKey]

Hi @Tockra 👋

I think proper solution requires support of https://github.com/testcontainers/testcontainers-rs/issues/577 So this should allow to define static/oncecell containers.

For now I have one workaround in mind, not ideal - but it should work. I'll share a bit later.

Also you could consider custom test harness (or some ready ones), e.g: https://www.infinyon.com/blog/2021/04/rust-custom-test-harness/

[Tockra]

Okay thank you. I'm looking forward to your solution.

Currently I have this solution:

static KEYCLOAK: OnceCell<(ContainerAsync<GenericImage>, String)> = OnceCell::const_new();

async fn start_auth_container() -> &'static (ContainerAsync<GenericImage>, String) {
    KEYCLOAK
        .get_or_init(|| async { start_keycloak_container().await })
        .await
}


#[tokio::test]
async fn test1(
) {
    let keycloak = start_auth_container().await;

    println!("{:?}", keycloak.1);
    //let app = start_app("some").await;
}

#[tokio::test]
async fn test2(
) {
    let keycloak = start_auth_container().await;

    println!("{:?}", keycloak.1);
    //let app = start_app("some").await;
}

#[tokio::test]
async fn test3(
) {
    let keycloak = start_auth_container().await;

    println!("{:?}", keycloak.1);
    //let app = start_app("some").await;
}

But the problem is, that the containers does not stop after the test suite execution, which is very annoying.

[DDtKey]

As a quick workaround, you might consider using something like this (your code was used for demonstration):

static KEYCLOAK: OnceLock<Mutex<Weak<(ContainerAsync<GenericImage>, String)>>> = OnceLock::new();

async fn start_auth_container() -> Arc<ContainerAsync<GenericImage>, String> {
        let mut guard = KEYCLOAK
            .get_or_init(|| Mutex::new(Weak::new()))
            .lock()
            .await;

        if let Some(container) = guard.upgrade() {
            Ok(container)
        } else {
            let container = Arc::new(start_keycloak_container().await);
            *guard = Arc::downgrade(&client);

            Ok(container)
        }
}

There are main points:

• it uses Weak in order not to prevent Drop of being called
• we initialize a new instance only if there is not one already in use

The issue with this approach: it depends on the parallelism of the tests, when executed sequentially, a new container will be created each time.

[Tockra]

Hm okay. For the beginning this looks nice. But I don't really understand what you mean with " it depends on the parallelism of the tests," . Currently I've 3 tests annotated with tokio::test and all these tests causes a new docker container. But this is far away from my ideal solution, because I explicitly want only one container !?

[DDtKey]

But I don't really understand what you mean with " it depends on the parallelism of the tests,"

I meant that if these tests are run concurrently, then in this case they will only use 1 instance of the container with the proposed solution. Because there is an active Arc and a Weak can be upgraded.

But on the other hand, if you run with --test-threads=1 or the tests for some reason have long pauses between them - they will most likely start a new container each time.

But usually (and by default) tests are executed in parallel, so this solution should be suitable for most cases, until the resource reaper is completed.

[rosvit]

Hello, I've ran into the same issue and I can confirm that @DDtKey's solution using OnceLock /Weak is working for parallel tests.

Regarding the first proposed solution using OnceCell:

But the problem is, that the containers does not stop after the test suite execution, which is very annoying.

If you need serial test execution using #[serial], workaround could be to forcibly stop and remove docker container in #[dtor]:

static CONTAINER: OnceCell<ContainerAsync<GenericImage>> = OnceCell::const_new();

// get_or_init of CONTAINER as you have in your snippet

#[dtor]
fn on_shutdown() {
    let container_id = CONTAINER.get().map(|c| c.id())
        .expect("failed to get container id");
    std::process::Command::new("docker")
        .args(["container", "rm", "-f", container_id])
        .output()
        .expect("failed to stop testcontainer");
}

[Tockra]

Hello, I've ran into the same issue and I can confirm that @DDtKey's solution using OnceLock /Weak is working for parallel tests.

Regarding the first proposed solution using OnceCell:

But the problem is, that the containers does not stop after the test suite execution, which is very annoying.

If you need serial test execution using #[serial], workaround could be to forcibly stop and remove docker container in #[dtor]:

static CONTAINER: OnceCell<ContainerAsync<GenericImage>> = OnceCell::const_new();

// get_or_init of CONTAINER as you have in your snippet

#[dtor]
fn on_shutdown() {
    let container_id = CONTAINER.get().map(|c| c.id())
        .expect("failed to get container id");
    std::process::Command::new("docker")
        .args(["container", "rm", "-f", container_id])
        .output()
        .expect("failed to stop testcontainer");
}

Thank you rosvit. Your solution is perfect for my usecase. Because we don't use a async call here, everything works fine. Before I ran with dtor into https://github.com/mmastrac/rust-ctor/issues/304 but without using tokio async stuff it works ;)

[symbx]

Another WA is to make cleanup synchronous without manual calls to docker.

• Add sync feature to tokio:

tokio = { version = "1.39", features = ["rt-multi-thread", "macros", "sync"] }

• Replace unbounded channels with bounded:

fn channel<T>() -> Channel<T> {
    let (tx, rx) = mpsc::channel(32);
    Channel { tx, rx: Mutex::new(rx) }
}

• Make cleanup method sync:

fn clean_up() {
    SRV_INPUT.tx.blocking_send(ContainerCommands::Stop).unwrap();
    SRC_STOP.rx.blocking_lock().blocking_recv().unwrap();
}

• And finally make destructor sync:

#[ctor::dtor]
fn on_destroy() {
    clean_up();
}

[Tockra]

fn clean_up() {
    SRV_INPUT.tx.blocking_send(ContainerCommands::Stop).unwrap();
    SRC_STOP.rx.blocking_lock().blocking_recv().unwrap();
}

What is SRV_INPUT and SRC_STOP?

[symbx]

It's same as - MONGODB_IN - RUN_FINISHED

In my case RUN_FINISHED uses same channel type, i didn't check on possibility of using blocking for tokio::sync::Notify

[lloydmeta]

Thanks @symbx , I built on your hints and what @Tockra had in the original post and it works like a charm

A complete working example is at https://github.com/lloydmeta/miniaturs/blob/d244760f5039a15450f5d4566ffe52d19d427771/server/src/test_utils/mod.rs#L12-L113

[JadKHaddad]

Is it safe to call std functions inside #[dtor]?

#[dtor] fn on_shutdown() { let container_id = CONTAINER.get().map(|c| c.id()) .expect("failed to get container id"); std::process::Command::new("docker") .args(["container", "rm", "-f", container_id]) .output() .expect("failed to stop testcontainer"); }

[ufoscout]

I implemented a small library as a workaround for this specific issue, you can check it here:

• library: https://crates.io/crates/maybe-once
• how to use it with testcontainers: https://github.com/ufoscout/maybe-once/blob/master/examples/testcontainers/src/postgres_blocking.rs

It allows the start of a single container before tests run, and then drops it when all tests terminate. It works both for sync and async containers. I hope it can help.