logger.warn("Failed to release operation lock: operation={}", operationName, e);
        }
    }

    /**
     * Checks whether the specified operation is currently running (lock held by an active instance).
     *
     * @param operationName the operation name to check.
     * @return {@code true} if the operation is running.
     */
    public boolean isOperationRunning(final String operationName) {

        },
        "hungarian_keywords": {
          "type":       "keyword_marker",
          "keywords": ["Helló", "világ", "keresés"]
        },
        "hungarian_stemmer": {

        },
        "hungarian_keywords": {
          "type":       "keyword_marker",
          "keywords": ["Helló", "világ", "keresés"]
        },
        "hungarian_stemmer": {