vectordotdev/vector · warning

Invalid value in $DOCKER_HOST

Error message

Invalid value in $DOCKER_HOST

What it means

vdev's detect_docker_socket reads the DOCKER_HOST environment variable and expects it to be valid UTF-8 (into_string().expect("Invalid value in $DOCKER_HOST")) and then a unix:// socket path. If DOCKER_HOST is set to a non-UTF-8 value, the first expect panics; this is distinct from the follow-up panic for non-unix:// values. The function only supports local unix sockets, not TCP Docker hosts.

Solutions

1. Inspect the variable: `printf '%s' "$DOCKER_HOST" | xxd` to spot invalid bytes, then unset it (`unset DOCKER_HOST`) to fall back to /var/run/docker.sock.
2. Set DOCKER_HOST to a clean value such as unix:///var/run/docker.sock.
3. Check ~/.bashrc, ~/.zshrc, or CI config for a script that writes a malformed DOCKER_HOST and fix it.
4. In code, replace the expect with from_utf8 handling on the OsString and a clear anyhow error, or support tcp:// hosts instead of assuming unix://.

Example fix

// before
Some(host) => host
    .into_string()
    .expect("Invalid value in $DOCKER_HOST")
// after
Some(host) => host.into_string().map_err(|bad|
    anyhow!("$DOCKER_HOST is not valid UTF-8: {:?}", bad)
)?

# before running vdev
python3 -c "import os,sys; v=os.environ.get('DOCKER_HOST',''); v.encode('utf-8'); sys.exit(0 if (not v or v.startswith('unix://')) else 1)" || { echo 'DOCKER_HOST must be UTF-8 unix:// socket path'; exit 1; }

match env::var_os("DOCKER_HOST") {
    Some(host) => match host.into_string() {
        Ok(s) => /* proceed, validate unix:// prefix */,
        Err(bad) => return Err(anyhow!("$DOCKER_HOST is not valid UTF-8: {:?}", bad)),
    },
    None => /* default socket */,
}

When it happens

Trigger: Having DOCKER_HOST exported with non-UTF-8 bytes in the value (e.g. mangled by a shell/profile script), then running any vdev command that resolves the Docker socket.

Common situations: DOCKER_HOST set by tooling (docker-machine, docker context) with unexpected content; corrupted shell profile exporting garbage; copy-pasted value with invisible/non-UTF-8 characters.

Understand the failure class

Background: "is not a valid" / "Invalid ... value" environment variable errors: how libraries validate env vars and what to do when they reject yours — this error's family across 48 libraries.

Related errors

• Invalid config file name
• all json-file keys should be matched
• Failed to convert OsStr to &str for
• Integration has no environments
• not a valid path

AI-assisted analysis of vectordotdev/vector@bdb87aeaa4 (2026-09-16). Data as JSON: /api/errors/2cb368a8fb488d9c. Report an issue: GitHub.

Appendix: source

Thrown at vdev/src/testing/docker.rs:40

        if Command::new(tool)
            .arg("version")
            .stdout(Stdio::null())
            .stderr(Stdio::null())
            .spawn()
            .and_then(|mut child| child.wait())
            .is_ok_and(|status| status.success())
        {
            return OsString::from(String::from(tool));
        }
    }
    fatal!("No container tool could be detected.");
}

fn detect_docker_socket() -> PathBuf {
    match env::var_os("DOCKER_HOST") {
        Some(host) => host
            .into_string()
            .expect("Invalid value in $DOCKER_HOST")
            .strip_prefix("unix://")
            .expect("$DOCKER_HOST is not a socket path")
            .into(),
        None => "/var/run/docker.sock".into(),
    }
}

View on GitHub (pinned to bdb87aeaa4)