vectordotdev/vector · error

unknown output

Error message

unknown output

What it means

`send_batch_named` looks up the requested output name in `self.named_outputs` and panics with "unknown output" via `.expect()` when the name is not registered. Named outputs must first be created with `add_output`; the library treats sending to an unregistered name as a programming error rather than a recoverable condition.

Solutions

1. Call `add_output(name, output)` (or register the output in the source's `Output` definition) before sending to that name.
2. Verify the name string in `send_batch_named` exactly matches the registered output name — check for typos and casing.
3. Confirm you are using the same `SourceSender` instance that had the output registered.
4. If the name is dynamic, validate it against the registered output set before sending instead of letting it panic.

Example fix

// before
sender.send_batch_named("outb", events).await?; // panics if not added
// after
let recv = sender.add_output("outb", Output::default());
sender.send_batch_named("outb", events).await?;

// Check the name is registered before sending (at source setup time)
let registered: Vec<&str> = vec!["stdout", "errors"]; // names passed to add_output
assert!(registered.contains(&"stdout"), "output 'stdout' not registered via add_output");

fn output_exists(sender: &SourceSender, name: &str) -> bool {
    // if named_outputs is private, mirror registration in your own registry:
    registered_outputs().iter().any(|n| n == name)
}

// Panics are not catchable normally; validate instead, or isolate:
let ok = std::panic::catch_unwind(std::panic::AssertUnwindSafe(|| {
    futures::executor::block_on(sender.send_batch_named(name, events))
}));
if ok.is_err() { /* unknown output name: fix registration */ }

When it happens

Trigger: Calling `sender.send_batch_named(name, events)` with a name that was never passed to `add_output` on that same `SourceSender` instance — typically a typo, a renamed output, or sending on a different sender than the one configured.

Common situations: Custom sources that declare named outputs in one place but send under a slightly different name; refactors renaming outputs without updating send calls; configs referencing output names the source never registers (e.g. removed or conditionally-added outputs).

Understand the failure class

Background: "Not found" and "does not exist" errors: why "Task not found", "No such folder", and "Can't find" fire when a lookup comes back empty — this error's family across 14 libraries.

Related errors

• no default output
• can't run runner twice
• Couldn't broadcast config changes.
• Encountered a connection-time error during runtime
• error creating request

AI-assisted analysis of vectordotdev/vector@bdb87aeaa4 (2026-09-16). Data as JSON: /api/errors/826fe683ddac26c0. Report an issue: GitHub.

Appendix: source

Thrown at lib/vector-core/src/source_sender/sender.rs:291

        E: Into<Event> + ByteSizeOf,
        I: IntoIterator<Item = E>,
        <I as IntoIterator>::IntoIter: ExactSizeIterator,
    {
        self.default_output_mut().send_batch(events).await
    }

    /// Send a batch of events event to a named output.
    ///
    /// This internally handles emitting [EventsSent] and [ComponentEventsDropped] events.
    pub async fn send_batch_named<I, E>(&mut self, name: &str, events: I) -> Result<(), SendError>
    where
        E: Into<Event> + ByteSizeOf,
        I: IntoIterator<Item = E>,
        <I as IntoIterator>::IntoIter: ExactSizeIterator,
    {
        self.named_outputs
            .get_mut(name)
            .expect("unknown output")
            .send_batch(events)
            .await
    }
}

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