WaitFor command exit with 0

[tisonkun]

Some image, like Postgres, would have a best match wait strategy like pg_isready returns 0.

Maybe we can implement such a wait strategy for testing with command?

[DDtKey]

Hi @tisonkun 👋

Could you elaborate on this, please?

In general, both WaitFor(starting from 0.20.0) and CmdWaitFor supports waiting for exit code.

Also, Image implementation can override exec_after_start, returning ExecCommands with their own CmdWaitFor (including exit code)

But I'm not sure I got the request correctly

[tisonkun]

Also, Image implementation can override exec_after_start, returning ExecCommands with their own CmdWaitFor (including exit code)

This seems the way I'd like to go.

If exec_after_start can block start and thus start will finish after exec_after_start success (with retry), then it sounds a good solution.

[DDtKey]

Yes, these commands are executed before returning Container instance form the start

But there is no retries of the command itself. We retry only the check of the exit status (because it might be a long-running command). Workaround could be to include retry logic in the command itself (loop for example)

But sounds like a candidate for a separate config option 🤔

[tisonkun]

@DDtKey I try:

    fn exec_after_start(&self, _: ContainerState) -> Result<Vec<ExecCommand>, TestcontainersError> {
        Ok(vec![ExecCommand::new([
            "pg_isready",
            "-U",
            USERNAME,
            "-d",
            "postgres",
        ])
        .with_cmd_ready_condition(CmdWaitFor::exit_code(0))])
    }

But it panics with called Result::unwrap()on anErr value: Exec(ExitCodeMismatch { expected: 0, actual: 2 }) insteadof retry until exit with 0.

[DDtKey]

Yes, as I mentioned above - there is no retry of the command itself for now. It seems to be a candidate for a separate feature(?).

But as a workaround you may consider to use while or until loops with bash for example 🤔

Something like:

until pg_isready -U USERNAME -d postgres; do sleep 1; done

[DDtKey]

Btw, speaking of postgres, do such conditions not work for you?

https://github.com/testcontainers/testcontainers-rs-modules-community/blob/66bbad597d4bbed30ef210e6a0afdb64089a3bb7/src/postgres/mod.rs#L86 (based on this issue)

These ones are widely used across different implementations of testcontainers (Java, Go, etc)

I'd like to know if there are any issues, because it may improve the existing community module.

[ns-sjorgedeaguiar]

Here's my workaround to wait until a command finishes and printing errors when the exit code is not 0:

let mut result = self
    .container
    .exec(ExecCommand::new(cmd))
    .await
    .expect("Failed to execute command in container");

let mut timeout = Duration::from_secs(5);
let mut exit_code = result.exit_code().await?;
loop {
    if exit_code.is_some() {
        break;
    }

    tokio::time::sleep(Duration::from_millis(100)).await;
    timeout -= Duration::from_millis(100);

    if timeout.as_millis() <= 0 {
        return Err("Timeout while waiting command to finish".into());
    }

    exit_code = result.exit_code().await?;
}

match exit_code {
    Some(0) => {}
    _ => {
        let code = result.exit_code().await?.unwrap_or(-1);
        let mut buffer = String::new();
        let mut stderr = result.stderr();
        stderr.read_to_string(&mut buffer).await?;
        buffer.split('\n').for_each(|line| {
            if !line.is_empty() {
                eprintln!("stderr: {}", line);
            }
        });
        return Err(format!("Failed to execute command (code = {})", code).into());
    }
};

Might be useful for you case as well.

[DDtKey]

I think ability to retry command should be incorporated into testcontainers. See no issues with that. Let's keep this item, I'll implement it later if if no one willing to contribute appears (any help is appreciated since I have limited bandwidth and a number of needed features)

[AntoinePrv]

I came looking for this for Postgres as well. The message on stdout can do for me, but it would be nice to be able to use pg_isready.

For instance, testcontainers Node has:

.withWaitStrategy(Wait.forSuccessfulCommand(`pg_isready -d ${POSTGRES_DB}`))

https://node.testcontainers.org/features/wait-strategies/#shell-command

[DDtKey]

I’m curious if #814 addresses the issue.

It’s slightly different, but it’s quite natural for Docker. It allows you to set a custom healthcheck (including a cmd, the number of retries, and so on) and utilize the healthcheck wait strategy.