thanos-io/thanos · critical

create syncer

Error message

create syncer

What it means

After building the meta fetcher, compact.NewSyncer assembles the block syncer (including the partitioner and duplicate-block filtering). Failure to construct it is wrapped as 'create syncer'. This is an initialization error, not a data-sync error, and typically indicates invalid configuration handed to NewSyncer.

Solutions

1. Inspect the wrapped inner error for which syncer component rejected the options.
2. Validate any relabel config flags passed to the command with `promtool check config` equivalent relabel rules.
3. Upgrade/align Thanos version if options changed (check NewSyncer signature/options for your release).
4. Retry with default options to isolate which custom flag causes the construction failure.

Example fix

// before (invalid relabel config passed to syncer filters)
--deduplication.replica-label=replica,extra
// after
--deduplication.replica-label=replica

// Validate relabel configs before constructing the syncer
for _, cfg := range relabelConfigs {
    if _, err := relabel.ParseConfig(cfg); err != nil {
        return fmt.Errorf("invalid relabel config: %w", err)
    }
}

sy, err := compact.NewSyncer(logger, reg, bkt, fetcher, ..., filters...)
if err != nil {
    return fmt.Errorf("create syncer (check relabel/dedup flags and Thanos version): %w", err)
}

When it happens

Trigger: Running compact/replicate where NewSyncer returns an error at cmd/thanos/tools_bucket.go:897 — e.g. invalid relabel/accept-filters configuration, an invalid block-pick strategy, or a failure creating the underlying partitioner due to bad options.

Common situations: Passing invalid --deduplication.replacement or accept-filter relabel configs, unsupported option combinations after a Thanos upgrade, or a nil logger/registry dependency.

Understand the failure class

Background: "Invalid value" and "allowed values are" config errors: what your library rejected and how to fix it — this error's family across 41 libraries.

Related errors

• level is bigger then default set of
• get compaction levels
• initialize query range limits
• create index cache
• unknown sync strategy

AI-assisted analysis of thanos-io/thanos@35b8b99117 (2026-09-07). Data as JSON: /api/errors/5462e390ef6dd640. Report an issue: GitHub.

Appendix: source

Thrown at cmd/thanos/tools_bucket.go:897

					block.NewLabelShardedMetaFilter(relabelConfig),
					block.NewConsistencyDelayMetaFilter(logger, tbc.consistencyDelay, extprom.WrapRegistererWithPrefix(extpromPrefix, reg)),
					ignoreDeletionMarkFilter,
					duplicateBlocksFilter,
				},
			)
			sy, err = compact.NewMetaSyncer(
				logger,
				reg,
				insBkt,
				cf,
				duplicateBlocksFilter,
				ignoreDeletionMarkFilter,
				stubCounter,
				stubCounter,
				0,
			)
			if err != nil {
				return errors.Wrap(err, "create syncer")
			}
		}

		level.Info(logger).Log("msg", "syncing blocks metadata")
		if err := sy.SyncMetas(ctx); err != nil {
			return errors.Wrap(err, "sync blocks")
		}

		level.Info(logger).Log("msg", "synced blocks done")

		compact.BestEffortCleanAbortedPartialUploads(ctx, logger, sy.Partial(), insBkt, stubCounter, stubCounter, stubCounter, ignoreDeletionMarkFilter.DeletionMarkBlocks())
		if _, err := blocksCleaner.DeleteMarkedBlocks(ctx); err != nil {
			return errors.Wrap(err, "error cleaning blocks")
		}

		level.Info(logger).Log("msg", "cleanup done")
		return nil
	})

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