risingwavelabs/risingwave · error · MetaError

no fragment connection from source fragment {} to source bac

Error message

no fragment connection from source fragment {} to source backfill fragment {}

What it means

During creation of a source backfill (streaming job rewrite), the code looks up a fragment_relation row from source_fragment_id to the source backfill fragment; if none exists it returns 'no fragment connection from source fragment {} to source backfill fragment {}'. The persisted fragment graph lacks the mandatory NoShuffle dispatch edge these fragments must have.

Source

Thrown at src/meta/src/controller/fragment.rs:1747

    /// (`backfill_actor_id`, `upstream_source_actor_id`)
    pub async fn get_running_actors_for_source_backfill(
        &self,
        source_backfill_fragment_id: FragmentId,
        source_fragment_id: FragmentId,
    ) -> MetaResult<Vec<(ActorId, ActorId)>> {
        let inner = self.inner.read().await;
        let txn = inner.db.begin().await?;

        let fragment_relation: DispatcherType = FragmentRelation::find()
            .select_only()
            .column(fragment_relation::Column::DispatcherType)
            .filter(fragment_relation::Column::SourceFragmentId.eq(source_fragment_id))
            .filter(fragment_relation::Column::TargetFragmentId.eq(source_backfill_fragment_id))
            .into_tuple()
            .one(&txn)
            .await?
            .ok_or_else(|| {
                anyhow!(
                    "no fragment connection from source fragment {} to source backfill fragment {}",
                    source_fragment_id,
                    source_backfill_fragment_id
                )
            })?;

        if fragment_relation != DispatcherType::NoShuffle {
            return Err(anyhow!("expected NoShuffle but got {:?}", fragment_relation).into());
        }

        let load_fragment_distribution_type = |txn, fragment_id: FragmentId| async move {
            let result: MetaResult<DistributionType> = try {
                FragmentModel::find_by_id(fragment_id)
                    .select_only()
                    .column(fragment::Column::DistributionType)
                    .into_tuple()
                    .one(txn)
                    .await

View on GitHub (pinned to 6469eb736d)

Solutions

1. Check fragment_relation rows for the reported source_fragment_id in the meta DB to see what edges exist
2. Verify cluster and table were created with a version supporting source backfill (upgrade if older)
3. Retry the operation; if the relation row is genuinely missing, the table's metadata is corrupted and may need recreation
4. Contact RisingWave support / file an issue with the job id and fragment ids if stock writes lose the relation

let rel = fragment_relation::Entity::find()
    .filter(fragment_relation::Column::SourceFragmentId.eq(src))
    .filter(fragment_relation::Column::TargetFragmentId.eq(dst))
    .one(&db).await?;
if rel.is_none() { return Err(skip_backfill()); }

match create_source_backfill(...).await { Err(e) if e.to_string().contains("no fragment connection") => log_corrupt_metadata(job_id), other => other }

When it happens

Trigger: Applying a source backfill rewrite for a table whose persisted fragment relations do not contain the expected source→source-backfill edge — e.g. meta data written by an older RisingWave version, partial write of the relation table, or a corrupted/edited meta store.

Common situations: Cluster upgraded across versions where backfill fragment layout changed; source backfill triggered on a table created before a migration; manual meta DB edits; interrupted DDL that wrote fragments without relations.

Understand the failure class

Background: Record Not Found Errors: "not found", RecordNotFound, and "was not found" — what they mean and how to fix them — this error's family across 28 libraries.

Related errors

• expected NoShuffle but got {:?}
• failed to find fragment: {}
• sink fragment not found for sink id {}
• Iceberg snapshot {snapshot_id} not found
• topic {} not found

AI-assisted analysis of risingwavelabs/risingwave@6469eb736d (2026-09-11). Data as JSON: /api/errors/38a8594e9d31cdb9. Report an issue: GitHub.