vectordotdev/vector · error

Invalid short volume mount format

Error message

Invalid short volume mount format: {s}

What it means

Thrown while preparing Docker Compose volumes for integration tests. Short-form volume mounts (strings) must contain a `:` separator so the host source side can be extracted and validated against the top-level `volumes:` map. A short mount string without any colon cannot be parsed, so vdev rejects it with this message.

Solutions

1. Rewrite the offending short mount to include both parts, e.g. `mydata:/var/lib/data`.
2. Or convert the mount to long-form syntax `{ type: volume, source: mydata, target: /var/lib/data }` which takes the `source` field path instead.
3. Ensure the volume source (left side of `:`) is declared in the compose top-level `volumes:` map, since the parsed source is looked up there next.

Example fix

# before
services:
  test:
    volumes:
      - mydata

# after
services:
  test:
    volumes:
      - mydata:/var/lib/data

def valid_short_mount(v):
    return isinstance(v, str) and ':' in v and v.split(':', 1)[0]

for s in service_volumes:
    assert valid_short_mount(s), f"short volume mount needs 'source:target': {s}"

When it happens

Trigger: A compose service in the integration config declares `volumes: ["mydata"]` (or any string without `:`) and `prepare_compose_volumes` iterates it: `s.split_once(':')` returns None, triggering the error.

Common situations: Hand-editing a docker-compose test file and adding an anonymous/named volume as a bare string instead of `name:/container/path`; copy-pasting a long-form mount into the short list; YAML quoting issues collapsing `a:b` incorrectly.

Understand the failure class

Background: "Invalid ... format", "must be in format X", "does not look like a ..." — invalid argument format errors across CLI tools and libraries — this error's family across 17 libraries.

Related errors

• Could not find environment named
• environment is already up
• Integration has no environments
• No environment for is up.
• a record with a next ID must have an event count

AI-assisted analysis of vectordotdev/vector@bdb87aeaa4 (2026-09-16). Data as JSON: /api/errors/7a27f687ad526319. Report an issue: GitHub.

Appendix: source

Thrown at vdev/src/testing/integration.rs:443

    /// Unix permissions mask to allow everybody to read a file
    const ALL_READ: u32 = 0o444;
    /// Unix permissions mask to allow everybody to read a directory
    const ALL_READ_DIR: u32 = 0o555;

    /// Fix up potential issues before starting a compose container
    pub fn prepare_compose_volumes(
        config: &ComposeConfig,
        test_dir: &Path,
        environment: &Environment,
    ) -> Result<()> {
        for service in config.services.values() {
            if let Some(volumes) = &service.volumes {
                for volume in volumes {
                    let source = match volume {
                        VolumeMount::Short(s) => {
                            s.split_once(':').map(|(s, _)| s).ok_or_else(|| {
                                anyhow::anyhow!("Invalid short volume mount format: {s}")
                            })?
                        }
                        VolumeMount::Long { source, .. } => source,
                    };
                    let source = resolve_placeholders(source, environment);
                    if !config.volumes.contains_key(&source)
                        && !source.starts_with('/')
                        && !source.starts_with('$')
                    {
                        let path: PathBuf = [test_dir, Path::new(&source)].iter().collect();
                        add_read_permission(&path)?;
                    }
                }
            }
        }
        Ok(())
    }

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