What causes "Failed to close SNMP SET client for agent {host}:{port}" in apache/seatunnel?

Check the wrapped cause; if it is 'socket already closed' style, the failure is benign and lifecycle bookkeeping should prevent double close.

apache/seatunnel · warning · SnmpConnectorException

CLOSE_FAILED

CLOSE_FAILED

Error message

Failed to close SNMP SET client for agent {host}:{port}

What it means

SnmpSinkWriter.close() releases the SNMP client; if client.close() throws IOException, it is rethrown as SnmpConnectorException with CLOSE_FAILED. The underlying SNMP session (transport listener) could not be shut down cleanly during task cleanup.

Source

Thrown at seatunnel-connectors-v2/connector-snmp/src/main/java/org/apache/seatunnel/connectors/seatunnel/snmp/sink/SnmpSinkWriter.java:80

        } catch (IOException e) {
            throw new SnmpConnectorException(
                    SnmpConnectorErrorCode.WRITE_FAILED,
                    "Failed to set OID "
                            + request.getOid()
                            + " on SNMP agent "
                            + config.getHost()
                            + ":"
                            + config.getPort(),
                    e);
        }
    }

    @Override
    public void close() {
        try {
            client.close();
        } catch (IOException e) {
            throw new SnmpConnectorException(
                    SnmpConnectorErrorCode.CLOSE_FAILED,
                    "Failed to close SNMP SET client for agent "
                            + config.getHost()
                            + ":"
                            + config.getPort(),
                    e);
        }
    }

    interface SnmpSetClientFactory {
        SnmpSetClient create(SnmpSinkConfig config) throws IOException;
    }
}

View on GitHub (pinned to cf67b549a7)

Solutions

Check the wrapped cause; if it is 'socket already closed' style, the failure is benign and lifecycle bookkeeping should prevent double close.
Ensure close() is invoked once per writer lifecycle (avoid calling after task teardown).
Log-and-continue may be appropriate for close failures since data already written cannot be undone by a retry.
Verify no other thread is using the client concurrently while close runs.
If persistent, restart the worker to reclaim transport resources.

Example fix

// before
writer.close();
writer.close(); // second call fails
// after
if (!writerClosed) { writer.close(); writerClosed = true; }

Defensive patterns

Strategy: fallback

Validate before calling

if (!writerClosed) { /* safe to close */ }

Try / catch

try {
    writer.close();
} catch (SnmpConnectorException e) {
    LOG.warn("SNMP sink close failed for {}:{} (data already flushed)", config.getHost(), config.getPort(), e);
}

Prevention

Invoke close exactly once per writer lifecycle.
Treat close failures as non-fatal: log and continue, since data was already sent.
Avoid concurrent use of the client while closing.
In tests, use @AfterAll-style single teardown to prevent repeated closes.

When it happens

Trigger: Calling close() on SnmpSinkWriter when the delegated Snmp4jSetClient.close() (SNMP4J snmp.close()) throws IOException — transport already broken or socket already closed.

Common situations: Agent/network died before close so the UDP transport is in an error state; close called twice (double lifecycle invocation); JVM teardown racing with the close; test harness closing the client repeatedly.

Understand the failure class

Background: "Invalid state transition" errors: "status must be X, actually Y", "already rejected/charging/uninstalled", "cannot ... while running" — what they mean when a library rejects your call — this error's family across 31 libraries.

Related errors

AI-assisted analysis of apache/seatunnel@cf67b549a7 (2026-09-10). Data as JSON: /api/errors/763f18d1dcec7efb. Report an issue: GitHub.