@Override
    public void destroy() {
        if (this.executorService != null) {
            try {
                this.executorService.awaitTermination(TERMINATION_TIMEOUT_SECONDS, TimeUnit.SECONDS);
            } catch (final Exception e) {
                LOGGER.trace(e.getMessage(), e);
            }
            this.executorService = null;
        }
    }
The executor service used to create a {@link #buildRequestExecutorService}.
core/cas-server-core-util-api/src/main/java/org/apereo/cas/util/http/SimpleHttpClientFactoryBean.java