Telemetry historical backfill delivery errored; will retry o

Error message

Telemetry historical backfill delivery errored; will retry on next worker start

What it means

After a telemetry historical backfill attempt, some events failed to deliver (errors.length > 0), so the completion marker was not written and the next worker start retries the same window. Retries are safe by design: deterministic uuids plus noon-UTC timestamps let PostHog dedupe the overlap.

Source

Thrown at src/services/telemetry/backfill.ts:679

  // resolve while captures are still un-enqueued.
  await client.shutdown();

  if (errors.length === 0) {
    writeBackfillMarker({
      completedAt: new Date().toISOString(),
      throughDay: lastFullDay,
      eventCount: events.length,
      installId,
      version: BACKFILL_VERSION,
    });
    logger.info('SYSTEM', 'Telemetry historical backfill complete', {
      eventCount: events.length,
      throughDay: lastFullDay,
    });
  } else {
    // No marker: the next worker start retries with byte-identical events
    // (deterministic uuid + noon-UTC timestamps make the retry dedupable).
    logger.warn('SYSTEM', 'Telemetry historical backfill delivery errored; will retry on next worker start', {
      eventCount: events.length,
      errorCount: errors.length,
    });
  }
}

View on GitHub (pinned to e2d1df569a)

Solutions

Ensure outbound HTTPS to app.posthog.com is allowed
Restart the worker — the retry is idempotent thanks to event dedupe
If it keeps failing, capture the per-event errors logged alongside and review proxy/TLS configuration
Note that persistent failure only costs historical telemetry, never functionality

Defensive patterns

Strategy: retry

Prevention

Allow outbound HTTPS to app.posthog.com in firewalls and proxies
Restart the worker after network recovery — the retry dedupes overlap by design
Do not disable the worker to silence this; the marker only writes on full success

When it happens

Trigger: Transient network failure or PostHog 5xx/timeout during batch delivery; a subset of per-day batches failing while others succeed, leaving the run incomplete.

Common situations: Laptop offline or asleep mid-backfill; firewall or proxy blocking app.posthog.com; rate limiting on large backfills.

Related errors

AI-assisted analysis of thedotmack/claude-mem@e2d1df569a (2026-08-20). Data as JSON: /api/errors/7d3f1ced89b82f58. Report an issue: GitHub.