What causes " error while installing dependencies: {e:?} {}" in windmill-labs/windmill?

Identify the failing dependency from the display name in the message and the `[x] error while installing ` log line, then fix or remove that specific dependency entry

windmill-labs/windmill · error

error while installing dependencies

Error message

 error while installing dependencies: {e:?}
{}

What it means

In the per-dependency detached install thread (`try_install_one_detached`), if installing one dependency fails, Windmill logs `[x] error while installing <name>` and records the failure against that dependency, then bails with this message carrying the debug error and the dependency's display name, identifying which single dependency failed.

Solutions

Identify the failing dependency from the display name in the message and the `[x] error while installing <name>` log line, then fix or remove that specific dependency entry
Retry the job — installs are per-dependency and transient failures often succeed on retry
Pin a version that actually exists on the configured index for the failing package
If it is a private package, verify worker credentials and index URL

Example fix

# before
some-package==1.2.3
# after (version that exists on the index)
some-package==1.2.4

Defensive patterns

Strategy: retry

Validate before calling

// pre-validate each requirement resolves before submitting the job
// for pkg in $(cat requirements.txt); do pip download --no-deps -q "$pkg" -d /tmp || echo "bad: $pkg"; done

Try / catch

// catch and surface which dep failed
match res {
    Err(e) if e.to_string().contains("error while installing dependencies") => {
        let dep = e.to_string().lines().last().unwrap_or("");
        report_failed_dependency(dep);
    }
    other => other?,
}

Prevention

Resolve the full lockfile locally before deploying to catch bad pins early
Keep dependency lists minimal and pinned
Ensure worker network access/credentials to the package index
Pre-bake flaky dependencies into the worker image

When it happens

Trigger: A single dependency's install in the threaded path fails — bad coordinate, registry unreachable for that package, transient network blip mid-download, or the package no longer existing on the index.

Common situations: One broken pin among many deps in a large requirements list; a package temporarily removed from the index; transient network failure on one download; a rate-limited package registry.

Related errors

AI-assisted analysis of windmill-labs/windmill@e474e8803c (2026-09-03). Data as JSON: /api/errors/4bb3c84c31321eb2. Report an issue: GitHub.

Appendix: source

Thrown at backend/windmill-worker/src/universal_pkg_installer.rs:871

        None,
        false,
        &mut None,
        None,
        None,
    )
    .await
    {
        windmill_queue::append_logs(
            &job_id,
            &w_id,
            format!(
                "\n[x] - error while installing {}: {e:?}",
                &dep.display_name
            ),
            &conn,
        )
        .await;
        bail!(format!(
            "\n error while installing dependencies: {e:?}\n{}",
            &dep.display_name
        ));
    } else {
        if let Some(ref cb) = post_install {
            cb(&dep)?;
        }
        mark_success(dep.path.clone(), &job_id, &w_id).await;
        print_success(
            false,
            true,
            &job_id,
            &w_id,
            &dep.display_name,
            name_ml,
            counter_arc,
            total_to_install,
            start,

View on GitHub (pinned to e474e8803c)