What causes "Failed to write %d items to table %s after %d retries" in apache/seatunnel?

Increase DynamoDB write capacity (or use on-demand mode) / reduce sink parallelism and batch size to stay under throttling limits.

apache/seatunnel · critical · RuntimeException

Failed to write %d items to table %s after %d retries

Error message

Failed to write %d items to table %s after %d retries

What it means

DynamoDbSinkClient.flushWithRetry retries failed writes up to maxRetries; afterward, any still-pending (unprocessed or failed) WriteRequests cause this RuntimeException reporting the item count, table name, and retry count. It means the batch write permanently failed after exhausting retries.

Source

Thrown at seatunnel-connectors-v2/connector-amazondynamodb/src/main/java/org/apache/seatunnel/connectors/seatunnel/amazondynamodb/sink/DynamoDbSinkClient.java:195

                        delay);

                try {
                    Thread.sleep(delay);
                } catch (InterruptedException e) {
                    Thread.currentThread().interrupt();
                    throw new RuntimeException("Interrupted during retry", e);
                }
            }
        }

        if (!pendingRequests.isEmpty()) {
            log.error(
                    "Failed to write {} items to table '{}' after {} retries",
                    pendingRequests.size(),
                    tableName,
                    maxRetries);

            throw new RuntimeException(
                    String.format(
                            "Failed to write %d items to table %s after %d retries",
                            pendingRequests.size(), tableName, maxRetries));
        }
    }
}

View on GitHub (pinned to cf67b549a7)

Solutions

Increase DynamoDB write capacity (or use on-demand mode) / reduce sink parallelism and batch size to stay under throttling limits.
Increase maxRetries and backoff in the sink configuration for transient throttling.
Filter or split oversized items (>400KB) and fix invalid attribute values before writing.
Check the log lines just before the exception — they list the count and table; correlate with DynamoDB throttling metrics (ThrottledRequests, WriteThrottleEvents).

Example fix

// before
maxRetries = 3; batchSize = 25
// after: more retries, smaller batches
maxRetries = 10; batchSize = 10

Defensive patterns

Strategy: retry

Validate before calling

for (WriteRequest r : requests) {
    if (r instanceof WriteRequest && estimatedSize(r) > 400 * 1024) throw new IllegalArgumentException("Item exceeds 400KB DynamoDB limit");
}

Type guard

null

Try / catch

try { client.flushWithRetry(); } catch (RuntimeException e) { log.error("DynamoDB flush failed: {}", e.getMessage()); alertAndCheckpointReplay(); }

Prevention

Size the table capacity (or on-demand) for peak write throughput; watch WriteThrottleEvents metrics.
Keep batch size modest and items under 400KB.
Increase maxRetries with exponential backoff for throttling-prone workloads.

When it happens

Trigger: batchWriteItem repeatedly returns unprocessed items or errors (provisioned throughput exceeded, item size > 400KB, invalid items) across all maxRetries attempts, leaving pendingRequests non-empty at the end of flushWithRetry.

Common situations: DynamoDB table under-provisioned or in on-demand throttle due to hot partition keys; single items exceeding the 400KB DynamoDB limit; duplicate keys or invalid attribute values in the batch; sustained write rate above table capacity during bulk load.

Related errors

AI-assisted analysis of apache/seatunnel@cf67b549a7 (2026-09-10). Data as JSON: /api/errors/fa3c8e549ef8dc5c. Report an issue: GitHub.