feat: Implement before_connect callback to modify connect options.

[fiadliel]

Allows the user to see and maybe modify the connect options before each attempt to connect to a database. May be used in a number of ways, e.g.:

• adding jitter to connection lifetime
• validating/setting a per-connection password
• using a custom server discovery process

One approach to the issue in #3051
Also may help to fix #445

This is based on the signature suggestion from #3051. I'm not certain about the Error type used here; how should a user of the API represent an external error, sqlx::Error::Io?

Also, not sure how you would want this tested? The existing callback tests use a database connection which does not yet exist in this case.

[abonander]

@fiadliel if you rebase it should fix the build failure.

[fiadliel]

@abonander Rebased, thanks!

[abonander]

@fiadliel looks like the examples are failing to compile.

[fiadliel]

Fixed.

By the way, to show a concrete use case, I use this code to get a GCP access token (which has an expiry), this is then used as a password when connecting.

    PoolOptions::new()
        .before_connect(move |opts: &PgConnectOptions, _num_attempts| {
            let auth_manager = auth_manager.clone();
            Box::pin(async move {
                if let Ok(token) = auth_manager
                    .get_token(&["https://www.googleapis.com/auth/cloud-platform"])
                    .await
                {
                    Ok(Cow::Owned(opts.clone().password(token.as_str())))
                } else {
                    Err(sqlx::Error::Io(std::io::Error::other(
                        "failed to get token",
                    )))
                }
            })
        })

Updating the password in a background task is suboptimal, because (for various reasons) a background task is not guaranteed to run in time (e.g. there are systems that only run your code during an active request, and suspend them at other times).

[tmh-mfr]

Hey there! We are using SeaORM in a new project and would would love to have this feature. Same usecase as @fiadliel mentioned, just on the AWS side. We get an access token via IAM which is only valid for 15 min.

Is there anyway I can help with getting this merged?

[jason-johnson]

Hi, I'm using this on Azure myself and would love to have this feature as well. One thing though: this will help with the creation of new connections but what happens to connections in the pool with the old password (token in my case)? Perhaps there could be a way to add some user defined meta data on acquire or connect or whatever where we could e.g. set the time of the token that was used for that connection and then on on_release we could destroy any connections which have the invalid token.

[ib353]

Hi, I'm using this on Azure myself and would love to have this feature as well. One thing though: this will help with the creation of new connections but what happens to connections in the pool with the old password (token in my case)? Perhaps there could be a way to add some user defined meta data on acquire or connect or whatever where we could e.g. set the time of the token that was used for that connection and then on on_release we could destroy any connections which have the invalid token.

For AWS at least the old connections are fine - the token lasts for 15 minutes, but is only checked on connection. So once you're connected you can keep the connection open for hours. Are you sure Azure isn't the same?

[abonander]

@fiadliel this looks good now. If you rebase to fix the merge conflict and re-run CI, I'm prepared to merge this.

[abonander]

@fiadliel closing due to inactivity. Feel free to reopen as a new PR if you come back to this.