louislam/uptime-kuma · error · Error

Response max length cannot be more than ${RESPONSE_BODY_LENG

Error message

Response max length cannot be more than ${RESPONSE_BODY_LENGTH_MAX} bytes

What it means

validate() rejects response_max_length above RESPONSE_BODY_LENGTH_MAX, which is 1024*1024 (1048576 bytes, 1 MiB). Caps how much response body Uptime Kuma will store/inspect.

Source

Thrown at server/model/monitor.js:1640

     * @returns {void}
     * @throws {Error} If validation fails
     */
    validate() {
        if (this.interval < MIN_INTERVAL_SECOND) {
            throw new Error(`Interval cannot be less than ${MIN_INTERVAL_SECOND} seconds`);
        }

        if (this.retryInterval < MIN_INTERVAL_SECOND) {
            throw new Error(`Retry interval cannot be less than ${MIN_INTERVAL_SECOND} seconds`);
        }

        if (this.response_max_length !== undefined) {
            if (this.response_max_length < 0) {
                throw new Error(`Response max length cannot be less than 0`);
            }

            if (this.response_max_length > RESPONSE_BODY_LENGTH_MAX) {
                throw new Error(`Response max length cannot be more than ${RESPONSE_BODY_LENGTH_MAX} bytes`);
            }
        }

        // Validate JSON fields to prevent invalid JSON from being stored in database
        if (this.kafkaProducerBrokers) {
            try {
                JSON.parse(this.kafkaProducerBrokers);
            } catch (e) {
                throw new Error(`Kafka Producer Brokers must be valid JSON: ${e.message}`);
            }
        }

        if (this.kafkaProducerSaslOptions) {
            try {
                JSON.parse(this.kafkaProducerSaslOptions);
            } catch (e) {
                throw new Error(`Kafka Producer SASL Options must be valid JSON: ${e.message}`);
            }

View on GitHub (pinned to 6b5ea01557)

Solutions

1. Cap response_max_length at 1048576 bytes, or leave it at 0 for the default/unlimited handling
2. Note the unit is bytes, not KB/MB: 2 means 2 bytes, not 2 megabytes

Example fix

// before
monitor.response_max_length = 5000000;

// after
monitor.response_max_length = 1048576;

const RESPONSE_BODY_LENGTH_MAX = 1024 * 1024;
if (monitor.response_max_length !== undefined && monitor.response_max_length > RESPONSE_BODY_LENGTH_MAX) throw new Error(`response_max_length must be <= ${RESPONSE_BODY_LENGTH_MAX} bytes`);

const RESPONSE_BODY_LENGTH_MAX = 1024 * 1024;
function isValidResponseMaxLength(v) { return v === undefined || (Number.isFinite(v) && v >= 0 && v <= RESPONSE_BODY_LENGTH_MAX); }

try { await socket.emit("addMonitor", payload); } catch (e) { /* surface e.message */ }

When it happens

Trigger: Saving a monitor with response_max_length greater than 1048576 bytes.

Common situations: User wants to capture large bodies; value entered in KB/MB units while the field expects raw bytes.

Related errors

• Interval cannot be less than ${MIN_INTERVAL_SECOND} seconds
• Retry interval cannot be less than ${MIN_INTERVAL_SECOND} se
• Response max length cannot be less than 0
• Kafka Producer Brokers must be valid JSON: ${e.message}
• Kafka Producer SASL Options must be valid JSON: ${e.message}

AI-assisted analysis of louislam/uptime-kuma@6b5ea01557 (2026-08-12). Data as JSON: /api/errors/7e60c956dbb145bf. Report an issue: GitHub.