What causes "Failed to fetch table changes for {}" in apache/iceberg?

Check the nested exception for catalog access problems and fix connectivity/credentials

Failed to fetch table changes for {}

Error message

Failed to fetch table changes for {}

What it means

MonitorSource's change reader iterator fetches new table changes (snapshots since lastSnapshotId) so downstream tasks can react to rewrites/expirations. If reading the changes throws, it logs a warning with the table name and returns TableChange.empty(), meaning the trigger cycle sees no change and maintenance proceeds based on scheduled triggers rather than table activity. The error is swallowed by design to keep the monitoring source alive.

Source

Thrown at flink/v2.2/flink/src/main/java/org/apache/iceberg/flink/maintenance/operator/MonitorSource.java:147

          if (snapshot != null) {
            if (!DataOperations.REPLACE.equals(snapshot.operation())) {
              LOG.debug("Reading snapshot {}", snapshot.snapshotId());
              event.merge(new TableChange(snapshot, table));
            } else {
              LOG.debug("Skipping replace snapshot {}", snapshot.snapshotId());
            }

            checking = snapshot.parentId();
          } else {
            // If the last snapshot has been removed from the history
            checking = null;
          }
        }

        lastSnapshotId = current;
        return event;
      } catch (Exception e) {
        LOG.warn("Failed to fetch table changes for {}", table, e);
        return TableChange.empty();
      }
    }

    @Override
    public String toString() {
      return MoreObjects.toStringHelper(this)
          .add("lastSnapshotId", lastSnapshotId)
          .add("maxReadBack", maxReadBack)
          .add("table", table)
          .toString();
    }
  }

  private static final class TableChangeIteratorSerializer
      implements SimpleVersionedSerializer<Iterator<TableChange>> {

    private static final int CURRENT_VERSION = 1;

View on GitHub (pinned to 86d9c8fc54)

Solutions

Check the nested exception for catalog access problems and fix connectivity/credentials
Coordinate expiration jobs with the maintenance monitor so it does not read removed snapshots
Verify the table still exists and the maintenance action's table identifier is correct
No code fix needed for transient errors — the next poll re-fetches changes from the last committed snapshot id

Defensive patterns

Strategy: fallback

Try / catch

// Library returns TableChange.empty() on failure; monitor logs:
// grep 'Failed to fetch table changes for' taskmanager.log

Prevention

Coordinate snapshot expiration with the monitor so referenced snapshots survive
Keep catalog credentials refreshed for long-running maintenance jobs
Confirm the monitored table exists and the identifier is correct

When it happens

Trigger: Raised in the iterator's next() when refreshing the table or building a SnapshotIterable/change reader between lastSnapshotId and the current snapshot throws — expired snapshots, catalog access errors, or corrupted snapshot metadata.

Common situations: Snapshot expiration by another job removing snapshots the reader expected; REST/Hive catalog auth token expiry; table dropped or renamed while the monitor runs; network partition to the catalog.

Related errors

AI-assisted analysis of apache/iceberg@86d9c8fc54 (2026-09-12). Data as JSON: /api/errors/5271357614ec40b6. Report an issue: GitHub.