Batch poster troubleshooting

This guide covers common operational issues that batch poster operators encounter, with guidance on diagnosing root causes and resolving them. For initial setup, see Run a batch poster. For fee-related tuning, see Batch poster fee tuning.

Batch poster balance management

The batch poster account is an Externally Owned Account (EOA) that pays gas fees on the parent chain to submit batch transactions. There is no automatic mechanism to keep this account funded—operators must monitor the balance and replenish it manually or through external automation.

Symptoms of low balance

• Batch posting transactions fail on the parent chain due to insufficient funds
• The batch poster logs show transaction submission errors
• Unposted batches accumulate, causing a growing backlog (see Batch posting backlog diagnosis)

Monitoring guidance

The Monitoring tools and considerations guide recommends monitoring the batch poster balance. In practice, this means:

• Query the balance directly: Use the parent chain RPC to check the batch poster EOA balance at regular intervals.
• Set up alerting: Configure external monitoring (e.g., a balance-checking script, onchain monitoring service, or infrastructure alerting tool) to notify you when the balance drops below a threshold.

Balance threshold guidance

There is no universally recommended balance threshold—the appropriate level depends on your parent chain's gas prices, your chain's batch posting frequency, and batch sizes. As a general approach, estimate your daily batch posting cost (number of batches per day multiplied by average gas cost per batch) and maintain a buffer of several days' worth of posting costs. Monitor actual spending over time and adjust accordingly.

Funding strategy

• Keep the account overfunded: The recommendation is to keep the batch poster account overfunded rather than maintaining a tight balance. This provides a buffer against gas price spikes.
• Automate top-ups if possible: Consider scripting periodic balance checks and transfers from a treasury account to the batch poster EOA.
• Monitor alongside gas prices: A balance that seems adequate during low gas prices may drain quickly during sustained gas spikes. Factor in parent chain gas price volatility when developing your funding strategy.

Mempool errors

"Posting this transaction will exceed max mempool size"

This error indicates that the parent chain node's mempool has rejected a transaction from the batch poster because it was at capacity.

What causes this error

• Too many pending transactions: The batch poster has submitted multiple transactions that haven't yet been included in a block, and the parent chain node's mempool has reached its limit for pending transactions from a single account or overall.
• Gas price too low for inclusion: If gas prices have risen since the transactions were submitted, older transactions may remain in the mempool and not be included. New submissions then push against the mempool’s size limits.
• RBF not escalating fast enough: When using DB or Redis storage (which support RBF), the replacement fee schedule may not be aggressive enough to get transactions included during congestion, causing the mempool to fill with stale transactions.

Resolution

1. Check the parent chain's current gas prices and compare them to your data poster's fee cap configuration. If gas prices are above your --node.batch-poster.data-poster.target-price-gwei, the data poster can't bid high enough to cover the fee. See Batch poster fee tuning for guidance on adjustments.
2. Review your queued transaction storage configuration: If you're using DB or Redis storage, pending transactions accumulate and rely on RBF for inclusion. Consider whether your RBF schedule (--node.batch-poster.data-poster.replacement-times for non-blob batch poster, --node.batch-poster.data-poster.blob-tx-replacement-times for blob batch poster) is escalating fees quickly enough. See Queued transaction database selection for storage option details.
3. Consider Noop storage for parent chains without mempools: If your parent chain is an Arbitrum chain or another chain without a traditional mempool, Noop storage avoids this issue entirely by waiting for each transaction receipt before submitting the next one.

Mempool size limits

The exact mempool weight limits depend on the parent chain node’s configuration, not the batch poster itself. The batch poster does not control the parent chain node’s mempool size. If you are running your own parent chain node, consult its documentation for mempool configuration. If using a third-party RPC provider, the mempool limits are determined by the provider’s infrastructure.

ErrExceedsMaxMempoolSize→ “error posting batch”

• [DEBUG→WARN→ERROR over 5 min]—The next batch's nonce would exceed unconfirmed nonce + max-mempool-transactions, so it's held back.
• [CAUSE]—L1 is confirming the poster's transactions slowly, and the in-flight window (default: 18) is filled.
• [MEANING]—Normal back-pressure short-term; sustained means posts are stuck.
• [ACTION]—If persistent, check L1 confirmation/fees, consider raising max-mempool-transactions.

lack of L1 balance prevents posting transaction with desired fee cap

• [WARN]—The poster's wallet can't cover the target max cost, so the bid is capped at the available balance.
• [CAUSE]—Low parent-chain balance and/or high L1 fees.
• [ACTION]—Fund the L1 wallet (send-l1); watch arb/batchposter/wallet/eth.

a large batch posting backlog exists

• [INFO/WARN/ERROR]—Unposted messages are piling up; INFO: is recently hit L1 bounds, WARN at backlog > 10, ERROR at > 30.
• [CAUSE]—Posts not keeping up (fees, mempool cap, L1 congestion, or the poster is behind).
• [ACTION]—Investigate why posting is throttled; ERROR is an alerting threshold.

error fetching batch poster wallet balance / ...gas refunder balance

• [WARN]—Balance gauge update failed.
• [CAUSE]—L1 RPC hiccup.
• [MEANING]—Monitoring gap only, not a posting failure.
• [ACTION]—Ignore if transient.

Batch posting backlog diagnosis

A batch posting backlog occurs when the sequencer continues ordering transactions, but the batch poster can’t submit them to the parent chain at the same rate. This results in an accumulation of unposted messages.

Common causes

Cause	Description
Insufficient batch poster balance	The EOA does not have enough funds to pay parent chain gas fees
Gas prices exceeding fee cap	Parent chain gas prices are above --node.batch-poster.data-poster.target-price-gwei, causing the data poster to pause submissions
Parent chain congestion	Even with adequate fees, high parent chain congestion can delay transaction inclusion
Node sync issues	The batch poster node may have fallen behind in syncing with the parent chain, preventing accurate fee estimation or transaction submission
Reverted transactions (DB/Redis)	When using DB or Redis storage, a reverted batch posting transaction causes the batch poster to halt. Noop storage tolerates reverts and retries automatically

How to identify a backlog

• Monitor the SequencerInbox contract: Track the frequency of batch submissions to the parent chain. A sudden drop or stop in batch submissions indicates an issue.
• Check the sequencer's transaction backlog size: As noted in the Monitoring tools and considerations guide, a large and growing backlog can be a sign of network health issues.
• Review batch poster logs: Look for error messages related to transaction submission failures, fee estimation errors, or the data poster pausing.

Backlog metrics

The specific log messages and metrics that indicate a backlog depend on the Nitro node version and configuration. Operators should familiarize themselves with their node’s log output during normal operation so that deviations are easier to spot. Key log prefixes to watch for include BatchPoster: and DataPoster: entries.

Resolution approaches

1. Check the batch poster balance: ensures the EOA has sufficient funds on the parent chain.
2. Check the parent chain gas prices: If prices exceed your fee cap, either wait for prices to drop or increase --node.batch-poster.data-poster.target-price-gwei (see Batch poster fee tuning).
3. Verify parent chain connectivity: Ensure the batch poster node can reach the parent chain RPC endpoint and that the parent chain node is fully synced.
4. Check for reverted transactions: If using DB or Redis storage, a reverted transaction halts the batch poster. Check the batch poster logs for revert errors. Restarting the batch poster or clearing the queued transaction storage (with caution) may be necessary.
5. Review node sync status: Confirm the batch poster node is synced with both the Arbitrum chain and the parent chain.

Retry errors

"Failed to re-send transaction"

This error appears when the data poster attempts to resubmit a batch posting transaction (typically as part of RBF), and the resubmission fails.

What causes this error

• Nonce conflicts: The original transaction may have already been included onchain, making the replacement attempt invalid because the nonce has already been consumed.
• Storage inconsistencies: When using DB or Redis for queued transaction tracking, mismatches between the stored transaction state and the onchain state can cause resubmission failures. This can happen after a node restart if the storage wasn't cleanly synced.
• Parent chain rejection: The parent chain node may reject the replacement transaction for various reasons—the replacement fee isn't high enough (must be at least 10% higher for standard RBF), the transaction format is invalid, or the parent chain node is experiencing issues.

Error context

The exact phrasing and context of retry errors can vary across Nitro versions. The "failed to re-send transaction" message generally indicates an RBF attempt that didn't succeed. Check the surrounding log lines for more specific error details (for example, "nonce too low", "replacement transaction underpriced", or connection errors).

Resolution

1. Check if the original transaction was included: Query the parent chain for the batch poster’s latest nonce and compare it to what the data poster expects. If the original transaction was already included, the retry error is benign—the data poster should recover automatically on the next cycle.
2. Review the queued transaction storage: If using DB or Redis, the stored transaction state may be stale. A node restart typically resolves transient storage inconsistencies.
3. Check parent chain connectivity: Ensure the batch poster can reliably reach the parent chain RPC. Intermittent connectivity causes retry failures.
4. Inspect RBF fee escalation: If the error mentions “replacement transaction underpriced”, the fee increase between attempts may be insufficient. The parent chain typically requires at least a 10% fee increase for RBF. Review the blob-tx-replacement-times schedule—shorter intervals may not allow enough price movement between attempts.

Reverts and halting

Large gap between last seen and current block number, skipping check for reverts

• [WARN]—pollForReverts fell > 100 blocks behind the chain, so it skipped scanning the intervening blocks for reverted poster transactions and fast-forwarded.
• [CAUSE]—Node lag, a long pause, or a header-subscription stall.
• [MEANING]—Reverts in that skipped window won't be detected.
• [ACTION]—Usually transient; if frequent, investigate node sync/L1 RPC health.

Transaction from batch poster reverted

• [WARN→ERROR]—A batch posting transaction got a failed receipt on L1.
• [ERROR (not warn)]—When using persistent storage, it sets batchReverted and halts all further posting.
• [CAUSE]—Contract rejected the batch (e.g., message-count mismatch, bad sequence number, gas/blob issue).
• [ACTION]—Investigate txErr; restart clears the halt flag; a count mismatch after force-inclusion may need allow-posting-first-batch-when-sequencer-message-count-mismatch.

Error checking batch reverts

• [DEBUG/WARN]—Revert check failed.
• [DEBUG]—If the error contains "not found" (a benign parent-node inconsistency where one node served a header, another lacks), else WARN.
• [ACTION]—Ignore the DEBUG case; investigate persistent WARNs.

Nonce/sync

failed to update nonce with queue empty; falling back to using a recent block

• [WARN]—Couldn't get the finalized nonce, so it used a recent block instead. Safe because the queue is empty.
• [CAUSE]—Finality data unavailable/RPC issue.
• [ACTION]—Benign one-off; investigate if constant.

Failed to get current nonce

• [WARN]—Nonce refresh failed, but a previous nonce exists, so it's non-fatal.
• [CAUSE]—L1 RPC.
• [ACTION]—Ignore if transient.

Failed to get latest nonce

• [WARN]—Couldn't fetch the unconfirmed nonce this loop; The iteration backs off 10s (minWait).
• [ACTION]—Transient RPC.

failed to update tx poster balance / failed to update tx poster nonce

• [WARN]—Periodic state refresh in the data-poster loop failed; on balance failure, the loop backs off 10s.
• [ACTION]—Transient RPC.

DataPoster failed to send transaction

• [WARN]—The RPC SendTransaction call errored.
• [CAUSE]—Mempool rejection, underpriced, RPC issue.
• [MEANING]—The transaction stays queued and is retried.
• [ACTION]—Watch for repetition.

maybeLogError family—failed to replace-by-fee transaction / failed to re-send transaction

• [DEBUG/INFO → WARN/ERROR after 20 consecutive]—Per-nonce send/RBF errors that escalate if they persist. storage.ErrStorageRace starts DEBUG; ErrFutureReplacePending/ErrNonceTooHigh start INFO; anything else is immediate ERROR.
• [ACTION]—The escalated WARN/ERROR is the real signal—investigate then.

Fee/pricing

can't meet data poster fee cap obligations with current target max cost / can't meet current parent chain fees with current target max cost

• [INFO]—The computed fee cap can't cover the current L1 base fee/required cost.
• [CAUSE]—L1 fees spiked above the poster's escalation target, or balanced-capped.
• [ACTION]—If posts stall, tune the fee formula (target-price-gwei, urgency-gwei, max-fee-bid-multiple-bips) or fund the wallet.

submitting transaction with GasFeeCap less than latest basefee / ...BlobGasFeeCap less than latest blobfee

• [INFO]—Posting anyway with a cap below the current fee, expecting it to confirm as fees drop.
• [ACTION]—Normal during fee volatility; concerning only if posts never confirm.

unable to fetch suggestedTipCap from l1 client to update arb/batchposter/suggestedtipcap metric

• [WARN]—Couldn't get a tip suggestion for the metric.
• [MEANING]—Metric gap only.
• [ACTION]—Ignore if transient.

L1 bounds/reorg

Disabling batch posting due to batch being within reorg resistance margin from layer 1 minimum block or timestamp bounds

• [ERROR]—The batch's first message is within reorg-resistance-margin of the L1 minimum bound, so posting is refused this round.
• [CAUSE]—The margin guard (default 10m) protects against reorgs near the lower bound.
• [ACTION]—Expected safety behavior; set margin to 0 only if you accept the reorg risk.

disabling L1 bound as batch posting message is close to the maximum delay

• [ERROR]—Overriding the L1 block bound because messages are near max-delay; the l1-block-bound-bypass margin kicked in to avoid stalling.
• [ACTION]—Informational; means it chose to post over respecting the bounds.

not posting more messages because block number or timestamp exceed L1 bounds

• [INFO]—Stopped adding messages that fall outside the current L1 bound window.
• [ACTION]—Normal bounding behavior.

error getting max time variation on L1 bound block; falling back on latest block

• [WARN]—unknown L2 block bound config value; falling back on using finalized
• [ERROR]—Bound resolution issues; the latter means a bad l1-block-bound config value.
• [ACTION]—Fix the config value for the ERROR.

DataPoster is avoiding creating a mempool nonce gap

• [INFO]—Held a transaction back rather than create a nonce gap that a reorg could expose (predecessor not yet reorg-resistant).
• [ACTION]—Normal reorg-safety; the transaction is retried.

DA/fallback (AnyTrust/AltDA)

DA writer failed, operator action required

• [ERROR]—A non-fallback DA writer error; posting stops.
• [ACTION]—Investigate immediately—this is an explicit operator-action alert.

DA writer explicitly requested fallback

• [WARN]—A DA backend requested a fallback; the poster moves to the next writer/EthDA.
• [ACTION]—Check DA provider health; sustained fallback means degraded DA.

Related info

• DA writer reports message too large, will rebuild batch
• DA writers exhausted, will rebuild for EthDA
• EthDA fallback period complete, will retry AltDA

These pair with the da_success/da_failure/da_last_success metrics.

Lock/coordination and gas estimation

Error checking if we could acquire redis lock

• [WARN]—Redis lock check failed; it optimistically tries anyway.
• [CAUSE]—Redis connectivity.
• [ACTION]—Check Redis if high availability matters.

Not posting batches right now because another batch poster has the lock or this node is behind

• [DEBUG]—Normal on backup posters/when behind.
• [ACTION]—Expected; not an error.

Failed to estimate gas for EIP-7623 check 1/2

• [WARN]—An EIP-7623 calldata-cost estimation probe failed.
• [ACTION]—Usually transient; relevant only on EIP-7623 parent chains.

error estimating gas for batch

• [escalates via ephemeral handler]—Gas estimation failed (ErrNormalGasEstimationFailed); DEBUG→WARN→ERROR over 5 min.
• [CAUSE]—L1 state lag, reverting estimation, inbox not caught up.
• [ACTION]—Investigate if it reaches ERROR.

Config/startup

max-size is deprecated; use max-calldata-batch-size...

• [ERROR]—Deprecated flag in use.
• [ACTION]—Migrate to max-calldata-batch-size.

Disabling data poster storage, as parent chain appears to be an Arbitrum chain without a mempool

• [INFO]—Auto-switched to no-op storage on an Arbitrum parent.
• [ACTION]—Expected for L3s.

messagesPerbatch is somehow zero

• [WARN]—Defensive guard against a should-be-impossible state; defaults to 1.
• [ACTION]—Benign unless recurring.

The escalation rule to remember

Many of these (mempool size, storage race, gas estimation, nonce-too-high, accumulator-not-found) are logged quietly at first and only escalate to WARN/ERROR if they persist past ~1–5 minutes, and batchPosterFailureCounter increments only at ERROR level. So a single WARN is usually noise; a sustained one that reaches ERROR is the real signal. Pair these with the metrics: estimated_batch_backlog, wallet/eth, the dataposter/nonce/* gap, and da_failure.

Quick reference

Symptom	Likely cause	Resolution
Batch posting stopped, no error in logs	Batch poster balance depleted	Fund the batch poster EOA on the parent chain
"Mempool weight limit exceeded"	Too many pending transactions in parent chain mempool	Review fee cap settings; check RBF escalation schedule
Batches not posting during gas spike	Gas prices exceed --node.batch-poster.data-poster.target-price-gwei	Increase fee cap or wait for prices to normalize
"Failed to re-send transaction"	Nonce conflict or RBF underpriced	Check if original transaction was included; review fee escalation
Growing sequencer backlog	Multiple possible causes	Check balance, gas prices, parent chain connectivity, and node sync
Batch poster halted after revert	Using DB/Redis storage with a reverted transaction	Review revert cause; restart batch poster or clear storage
Blob transactions pending for hours	Blob tip cap too low	Increase max-blob-tx-tip-cap-gwei; review replacement schedule