apache/seatunnel · error · IllegalArgumentException

reconnect_timeout must be greater than 0, got: ${reconnectTi

Error message

reconnect_timeout must be greater than 0, got: ${reconnectTimeout}

What it means

MqttSourceConfig.validate throws IllegalArgumentException when reconnect_timeout is zero or negative. The value controls how long the source waits before attempting a reconnect after a lost MQTT connection, so it must be a positive duration. Validation fails fast at source construction.

Source

Thrown at seatunnel-connectors-v2/connector-mqtt/src/main/java/org/apache/seatunnel/connectors/seatunnel/mqtt/source/MqttSourceConfig.java:77

                    "client_id is required when clean_session=false for MQTT source");
        }
        this.clientId =
                isBlank(configuredClientId)
                        ? CLIENT_ID_PREFIX + UUID.randomUUID().toString()
                        : configuredClientId;

        validate();
    }

    private void validate() {
        if (qos < 0 || qos > 1) {
            throw new IllegalArgumentException("MQTT source qos must be 0 or 1, got: " + qos);
        }
        if (!"json".equalsIgnoreCase(format) && !"text".equalsIgnoreCase(format)) {
            throw new IllegalArgumentException("Unsupported MQTT source format: " + format);
        }
        if (reconnectTimeout <= 0) {
            throw new IllegalArgumentException(
                    "reconnect_timeout must be greater than 0, got: " + reconnectTimeout);
        }
        if (maxQueueSize <= 0) {
            throw new IllegalArgumentException(
                    "max_queue_size must be greater than 0, got: " + maxQueueSize);
        }
    }

    private static boolean isBlank(String value) {
        return value == null || value.trim().isEmpty();
    }

    public String getUrl() {
        return url;
    }

    public String getTopic() {
        return topic;

View on GitHub (pinned to cf67b549a7)

Solutions

1. Set reconnect_timeout to a positive value in the expected unit (e.g. 5000 for 5s if ms)
2. Do not attempt to disable reconnection via this option — set it to a sane retry interval instead
3. Verify units against MqttSourceOptions.RECONNECT_TIMEOUT definition in docs

Example fix

// before
Mqtt {
  reconnect_timeout = 0
}
// after
Mqtt {
  reconnect_timeout = 5000
}

if (reconnectTimeout <= 0) {
  throw new IllegalArgumentException("reconnect_timeout must be > 0, got: " + reconnectTimeout);
}

null

null

When it happens

Trigger: Setting reconnect_timeout = 0 or a negative number in the MQTT source config; also caused by unit mistakes (passing milliseconds where seconds expected, or vice versa, producing 0 after truncation).

Common situations: Copy-paste of option names with wrong units; users trying to 'disable' reconnection by setting 0 (not permitted); template configs with placeholder 0 values never replaced.

Understand the failure class

Background: "Invalid value" and "allowed values are" config errors: what your library rejected and how to fix it — this error's family across 41 libraries.

• Timeouts: ETIMEDOUT, deadlines, and hung requests — what actually expires when a request times out.

Related errors

• client_id is required when clean_session=false for MQTT sour
• MQTT source qos must be 0 or 1, got: ${qos}
• Unsupported MQTT source format: ${format}
• max_queue_size must be greater than 0, got: ${maxQueueSize}
• Schema config can not be empty

AI-assisted analysis of apache/seatunnel@cf67b549a7 (2026-09-10). Data as JSON: /api/errors/b1762bf60f2e9a61. Report an issue: GitHub.