xai-org/x-algorithm · error · anyhow::Error

Failed to check object existence: {}

Error message

Failed to check object existence: {}

What it means

Raised in the O2 wrapper's exists() when store.head(path) fails with an error other than NotFound. head() is being used to test object existence, so any non-NotFound failure (auth, network, malformed path, permission) surfaces as this generic message.

Source

Thrown at thunder/o2/mod.rs:116

        let path = self.full_path(key);
        let result = self
            .store
            .get(&path)
            .await
            .with_context(|| format!("Failed to get object: {}", path))?;
        let bytes = result
            .bytes()
            .await
            .with_context(|| format!("Failed to read object bytes: {}", path))?;
        Ok(bytes)
    }

    pub async fn exists(&self, key: &str) -> Result<bool> {
        let path = self.full_path(key);
        match self.store.head(&path).await {
            Ok(_) => Ok(true),
            Err(object_store::Error::NotFound { .. }) => Ok(false),
            Err(e) => Err(anyhow!("Failed to check object existence: {}", e)),
        }
    }

    pub async fn delete(&self, key: &str) -> Result<()> {
        let path = self.full_path(key);
        self.store
            .delete(&path)
            .await
            .with_context(|| format!("Failed to delete object: {}", path))?;
        Ok(())
    }

    pub async fn list(&self, key_prefix: &str) -> Result<Vec<String>> {
        let path = self.full_path(key_prefix);
        let prefix_str = format!("{}/", self.prefix);

        let objects: Vec<_> = self
            .store

View on GitHub (pinned to 24c60942c5)

Solutions

  1. Check credentials and permissions for the bucket/prefix used by full_path(key)
  2. Print and validate the fully-qualified path (full_path output) for malformed keys
  3. Retry once with backoff for transient network errors before surfacing
  4. Verify the object store URL scheme/bucket config (region, endpoint) matches the environment

Example fix

// before
if store.exists(key).await? { ... }

// after
let path = format_full_path(key);
tracing::debug!("HEAD {path}");
match store.exists(key).await {
    Ok(true) => { /* proceed */ }
    Ok(false) => { /* missing */ }
    Err(e) if is_transient(&e) => { /* retry once */ }
    Err(e) => return Err(anyhow!("exists({path}) failed: {e}")),
}
Defensive patterns

Strategy: retry

Validate before calling

// validate key before calling exists: no leading '/', no '..'; preflight store credentials

Try / catch

match store.exists(key).await { Err(e) if is_transient(&e) => retry_once(...).await, r => r }

Prevention

When it happens

Trigger: Calling exists(key) when the object store returns an error on HEAD: invalid credentials, bucket not accessible, DNS/network failure to S3/GCS/Azure, or an invalid object path produced by full_path(key).

Common situations: Missing/expired cloud credentials (AWS keys, GCP SA); wrong bucket or region in the store URL; network egress blocked from the container; key strings with characters that break path encoding.

Related errors

AI-assisted analysis of xai-org/x-algorithm@24c60942c5 (2026-08-28). Data as JSON: /api/errors/a9699b9393aa21cd. Report an issue: GitHub.