Enum DlqBackend 

#[non_exhaustive]
pub enum DlqBackend {
    File(FileDlqInner),
    Http(HttpDlqInner),
    Redis(RedisDlqInner),
}

Available on crate feature dlq only.

A DLQ backend. One variant per supported destination.

Variants are feature-gated:

• Self::File – always available
• [Self::Kafka] – dlq-kafka feature
• Self::Http – dlq-http feature
• Self::Redis – dlq-redis feature

Each variant’s inner struct lives in its sibling module (file::FileDlqInner, kafka::KafkaDlqInner, etc.). They are crate-private – consumers configure DLQ via super::DlqConfig and drive it via super::orchestrator::Dlq.

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

File(FileDlqInner)

NDJSON file backend with rotation.

Http(HttpDlqInner)

Available on crate feature dlq-http only.

HTTP POST backend.

Redis(RedisDlqInner)

Available on crate feature dlq-redis only.

Redis Streams backend.

Implementations

impl DlqBackend

pub async fn send_batch(&mut self, batch: &[DlqEntry]) -> Result<(), DlqError>

Write a batch of entries to this backend. Called only by the orchestrator’s drain task – never from a consumer hot path.

Errors

Backend-specific. The orchestrator decides whether to cascade, fall back, or fan out based on the configured super::DlqMode.

pub async fn flush_durable(&mut self) -> Result<(), DlqError>

Make every entry written so far DURABLE.

Called from the BackgroundSink barrier handler when a consumer invokes super::orchestrator::Dlq::flush. Each backend honours the strongest durability it can express:

• File: flush() on the rotating writer. The underlying file-rotate crate doesn’t expose the inner File handle, so we can’t fsync() from here – flush() only guarantees that buffered bytes have been handed to the kernel page cache. A power-loss event between page-cache and disk can still lose data. Documented limitation; tracked separately if/when file-rotate exposes a sync hook.
• Kafka: producer.flush() – blocks until every queued message has been acked by the broker (per the producer’s acks config). This is the real durability semantic.
• HTTP: no-op. send_batch already awaits the response.
• Redis: no-op. send_batch already awaits the XADD pipeline.

Errors

Backend-specific. Surfaced to the BackgroundSink barrier handler which logs and continues.

pub fn name(&self) -> &'static str

Backend name for log / metric labels.

Trait Implementations

impl Debug for DlqBackend

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.