databendlabs/databend · error · InvalidInput

semaphore permit key should have at least 3 segments

Error message

semaphore permit key should have at least 3 segments: {}

What it means

A generic input-validation guard in PermitKey::parse_key: after splitting the encoded key string with rsplitn(3, '/'), it must yield exactly three segments (seq, "queue", prefix). This error fires when the key string is malformed — missing slashes or fewer than three parts — typically because the stored key was corrupted or produced by an incompatible format.

Solutions

1. Ensure the key string passed to parse_key was produced by format_key and contains at least three '/'-separated segments.
2. If the key comes from persistent storage, check for corruption or truncation and re-derive or regenerate the permit key.
3. Before calling parse_key, validate that key.matches('/').count() >= 2 and handle invalid input explicitly.

When it happens

Trigger: Thrown at src/meta/plugins/semaphore/src/storage/permit_key.rs:62 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of databendlabs/databend@288d84d76e (2026-09-11). Data as JSON: /api/errors/14e10467a2e35f83. Report an issue: GitHub.

Appendix: source

Thrown at src/meta/plugins/semaphore/src/storage/permit_key.rs:62

    pub fn new(prefix: impl ToString, seq: PermitSeq) -> Self {
        Self {
            prefix: prefix.to_string(),
            seq,
        }
    }

    /// Format the key to a string, keep order preserving.
    pub fn format_key(&self) -> String {
        format!("{}/queue/{:020}", self.prefix, self.seq)
    }

    /// Parse the key from an encoded string.
    pub fn parse_key(key: &str) -> Result<Self, io::Error> {
        // split by the last 2 slashes:
        let parts = key.rsplitn(3, '/').collect::<Vec<_>>();

        if parts.len() != 3 {
            return Err(io::Error::new(
                io::ErrorKind::InvalidInput,
                format!(
                    "semaphore permit key should have at least 3 segments: {}",
                    key
                ),
            ));
        }

        if parts[1] != "queue" {
            return Err(io::Error::new(
                io::ErrorKind::InvalidInput,
                format!(
                    "semaphore permit key should have 'queue' as the second segment: {}",
                    key
                ),
            ));
        }

View on GitHub (pinned to 288d84d76e)