apache/flink · error · IllegalArgumentException

Line length limit must be at least 1.

Error message

Line length limit must be at least 1.

What it means

DelimitedInputFormat uses lineLengthLimit as a safety bound to detect unparseable/malformed records (records spanning more bytes than the limit abort reading with an IOException). A limit < 1 is meaningless and would reject every record, so setLineLengthLimit enforces a minimum of 1.

Source

Thrown at flink-core/src/main/java/org/apache/flink/api/common/io/DelimitedInputFormat.java:255

    public void setDelimiter(char delimiter) {
        setDelimiter(String.valueOf(delimiter));
    }

    public void setDelimiter(String delimiter) {
        if (delimiter == null) {
            throw new IllegalArgumentException("Delimiter must not be null");
        }
        this.delimiter = delimiter.getBytes(getCharset());
        this.delimiterString = delimiter;
    }

    public int getLineLengthLimit() {
        return lineLengthLimit;
    }

    public void setLineLengthLimit(int lineLengthLimit) {
        if (lineLengthLimit < 1) {
            throw new IllegalArgumentException("Line length limit must be at least 1.");
        }

        this.lineLengthLimit = lineLengthLimit;
    }

    public int getBufferSize() {
        return bufferSize;
    }

    public void setBufferSize(int bufferSize) {
        if (bufferSize < 2) {
            throw new IllegalArgumentException("Buffer size must be at least 2.");
        }

        this.bufferSize = bufferSize;
    }

    public int getNumLineSamples() {

View on GitHub (pinned to 2f3c205e92)

Solutions

1. Set a positive limit, e.g. format.setLineLengthLimit(1024 * 1024) for 1 MB records.
2. If you intend 'effectively unlimited', set a very large value such as Integer.MAX_VALUE.
3. Validate the configured limit is >= 1 before calling setLineLengthLimit.

Example fix

// before
format.setLineLengthLimit(maxRecordBytes); // maxRecordBytes == 0 -> throws

// after
int limit = maxRecordBytes > 0 ? maxRecordBytes : Integer.MAX_VALUE;
format.setLineLengthLimit(limit);

int limit = configuredLineLengthLimit > 0 ? configuredLineLengthLimit : Integer.MAX_VALUE;
format.setLineLengthLimit(limit);

When it happens

Trigger: Calling format.setLineLengthLimit(0) or any negative value.

Common situations: Misconfiguring the max record length from a property that defaulted to 0; passing -1 to mean 'unlimited' (this format has no unlimited sentinel — use a large value instead).

Related errors

• Delimiter must not be null
• Buffer size must be at least 2.
• Number of line samples must not be negative.
• Buffer size must be greater than length of delimiter.
• The block size parameter must be set and larger than 0.

AI-assisted analysis of apache/flink@2f3c205e92 (2026-08-14). Data as JSON: /api/errors/72ebdf475b1df0ad. Report an issue: GitHub.