CacheStore cannot be used on the worker node!…

Error message

CacheStore cannot be used on the worker node! queue_result_blocking was used.

What it means

CacheStore::queue_result_blocking (blocking wait for a queue result) is another panic! stub on worker nodes in cache_rocksstore.rs. A worker cannot block waiting on queue results since it does not own the queue, so any call panics with this message.

Solutions

Run the blocking result wait against the master node's store or a remote client to it
Fix node role assignment so queue-consuming/blocking code only runs on the master
If intentionally testing, instantiate the non-worker CacheStore variant

Example fix

// before
let r = worker_store.queue_result_blocking(key, timeout).await?;
// after
let r = master_client.queue_result_blocking(key, timeout).await?;

Defensive patterns

Strategy: validation

Validate before calling

if !is_master { return Err(CubeError::internal("blocking queue_result requires master node")); }
let r = master_client.queue_result_blocking(key, timeout).await?;

Type guard

fn is_queue_capable(store: &dyn CacheStore) -> bool { node_role == NodeRole::Master }

Try / catch

let r = std::panic::catch_unwind(AssertUnwindSafe(|| master_client.queue_result_blocking(key, timeout))).map_err(|_| CubeError::internal("queue_result_blocking called on worker node"))?;

Prevention

Run blocking waits on the master only
Never schedule blocking queue waits in worker processes
Verify role config after topology changes
Alert on any catch_unwind hit for this panic

When it happens

Trigger: Calling CacheStore::queue_result_blocking(key, timeout) on a worker-node store instance (cache_rocksstore.rs:2068).

Common situations: Blocking result wait executed inside a worker-mode CubeStore process; a deployment where the query-orchestration loop runs on workers instead of the master.

Related errors

AI-assisted analysis of cube-js/cube@7d981676b3 (2026-09-02). Data as JSON: /api/errors/df68d7ce39fc0aeb. Report an issue: GitHub.

Appendix: source

Thrown at rust/cubestore/cubestore/src/cachestore/cache_rocksstore.rs:2068

    async fn queue_ack(&self, _key: QueueKey, _result: Option<String>) -> Result<bool, CubeError> {
        panic!("CacheStore cannot be used on the worker node! queue_ack was used.")
    }

    async fn queue_result(
        &self,
        _key: QueueKey,
        _external_id: Option<String>,
    ) -> Result<Option<QueueResultResponse>, CubeError> {
        panic!("CacheStore cannot be used on the worker node! queue_result was used.")
    }

    async fn queue_result_blocking(
        &self,
        _key: QueueKey,
        _timeout: u64,
    ) -> Result<Option<QueueResultResponse>, CubeError> {
        panic!("CacheStore cannot be used on the worker node! queue_result_blocking was used.")
    }

    async fn queue_merge_extra(&self, _key: QueueKey, _payload: String) -> Result<(), CubeError> {
        panic!("CacheStore cannot be used on the worker node! queue_merge_extra was used.")
    }

    async fn compaction(&self) -> Result<(), CubeError> {
        panic!("CacheStore cannot be used on the worker node! compaction was used.")
    }

    async fn info(&self) -> Result<CachestoreInfo, CubeError> {
        panic!("CacheStore cannot be used on the worker node! info was used.")
    }

    async fn eviction(&self) -> Result<EvictionResult, CubeError> {
        panic!("CacheStore cannot be used on the worker node! eviction was used.")
    }

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