kestra-io/kestra · error · PebbleException

The 'nanoId()' function field 'length' must be greater than:

Error message

The 'nanoId()' function field 'length' must be greater than: 0

What it means

The nanoId() function validates that the length argument, if provided, is at least 1. A length of 0 or a negative number triggers this error. The default length is 21 if no length argument is given. Note that this check only fires when the length argument is present and is a Long (Pebble numeric literals are Long).

Source

Thrown at core/src/main/java/io/kestra/core/runners/pebble/functions/NanoIDFunction.java:58

                lineNumber,
                self.getName()
            );
        }
        if (alphabet.length > MAX_ALPHABET_LENGTH) {
            throw new PebbleException(
                null,
                "The 'nanoId()' function field 'alphabet' must not contain more than: " + MAX_ALPHABET_LENGTH + " characters",
                lineNumber,
                self.getName()
            );
        }
        return createNanoID(length, alphabet);
    }

    private static int parseLength(Map<String, Object> args, PebbleTemplate self, int lineNumber) {
        var value = (Long) args.get(LENGTH);
        if (value < 1) {
            throw new PebbleException(
                null,
                "The 'nanoId()' function field 'length' must be greater than: 0",
                lineNumber,
                self.getName()
            );
        }
        if (value > MAX_LENGTH) {
            throw new PebbleException(
                null,
                "The 'nanoId()' function field 'length' must be lower than: " + MAX_LENGTH,
                lineNumber,
                self.getName()
            );
        }
        return Math.toIntExact(value);
    }

    @Override

View on GitHub (pinned to 823fada927)

Solutions

Provide a length of at least 1: {{ nanoId(length=8) }}.
Omit the length argument to use the default of 21.
Guard dynamic length values: {% if myLen > 0 %}{{ nanoId(length=myLen) }}{% else %}{{ nanoId() }}{% endif %}.

Example fix

# before
value: "{{ nanoId(length=0) }}"
# after
value: "{{ nanoId(length=8) }}"

Defensive patterns

Strategy: validation

Validate before calling

# Ensure length is at least 1, or omit it for the default of 21:
{% if myLength is not null and myLength > 0 %}
  {{ nanoId(length=myLength) }}
{% else %}
  {{ nanoId() }}
{% endif %}

Prevention

Omit the length argument to use the default of 21.
Validate dynamic length variables are positive integers.
Guard against zero-length edge cases in conditional logic.

When it happens

Trigger: Calling {{ nanoId(length=0) }} or {{ nanoId(length=-5) }}. Passing a dynamic variable for length that resolves to 0 or a negative number.

Common situations: The author sets length from a variable that is conditionally computed and can be 0 in edge cases. The author misunderstands the function and passes 0 expecting a 'default' length.

Related errors

AI-assisted analysis of kestra-io/kestra@823fada927 (2026-08-14). Data as JSON: /api/errors/5534fa58c6dceaa7. Report an issue: GitHub.