elastic/elasticsearch · error · IllegalArgumentException

Setting [separator] must be a single, non-null character. [{

Error message

Setting [separator] must be a single, non-null character. [{}] was provided.

What it means

Error "Setting [separator] must be a single, non-null character. [{}] was provided." thrown in elastic/elasticsearch.

Source

Thrown at modules/analysis-common/src/main/java/org/elasticsearch/analysis/common/FingerprintAnalyzerProvider.java:59

        CharArraySet stopWords = Analysis.parseStopWords(env, settings, DEFAULT_STOP_WORDS);

        this.analyzer = new FingerprintAnalyzer(stopWords, separator, maxOutputSize);
    }

    @Override
    public FingerprintAnalyzer get() {
        return analyzer;
    }

    public static char parseSeparator(Settings settings) throws IllegalArgumentException {
        String customSeparator = settings.get(SEPARATOR.getPreferredName());
        if (customSeparator == null) {
            return DEFAULT_SEPARATOR;
        } else if (customSeparator.length() == 1) {
            return customSeparator.charAt(0);
        }

        throw new IllegalArgumentException(
            "Setting [separator] must be a single, non-null character. [" + customSeparator + "] was provided."
        );
    }
}

View on GitHub (pinned to db6a809a66)

When it happens

Trigger: Thrown at modules/analysis-common/src/main/java/org/elasticsearch/analysis/common/FingerprintAnalyzerProvider.java:59 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of elastic/elasticsearch@db6a809a66 (2026-08-12). Data as JSON: /api/errors/43239eacbedc689c. Report an issue: GitHub.