elastic/elasticsearch · error · IllegalArgumentException

Token filter [{}] cannot be used to parse synonyms

Error message

Token filter [{}] cannot be used to parse synonyms

What it means

Error "Token filter [{}] cannot be used to parse synonyms" thrown in elastic/elasticsearch.

Source

Thrown at modules/analysis-common/src/main/java/org/elasticsearch/analysis/common/FingerprintTokenFilterFactory.java:43

    private final char separator;
    private final int maxOutputSize;

    FingerprintTokenFilterFactory(IndexSettings indexSettings, Environment environment, String name, Settings settings) {
        super(name);
        this.separator = FingerprintAnalyzerProvider.parseSeparator(settings);
        this.maxOutputSize = settings.getAsInt(MAX_OUTPUT_SIZE.getPreferredName(), DEFAULT_MAX_OUTPUT_SIZE);
    }

    @Override
    public TokenStream create(TokenStream tokenStream) {
        TokenStream result = tokenStream;
        result = new FingerprintFilter(result, maxOutputSize, separator);
        return result;
    }

    @Override
    public TokenFilterFactory getSynonymFilter() {
        throw new IllegalArgumentException("Token filter [" + name() + "] cannot be used to parse synonyms");
    }

}

View on GitHub (pinned to db6a809a66)

When it happens

Trigger: Thrown at modules/analysis-common/src/main/java/org/elasticsearch/analysis/common/FingerprintTokenFilterFactory.java:43 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/a03ca77868d38ad6. Report an issue: GitHub.