final PingResponse pingResponse = searchEngineClient.ping();
            writeJsonResponse(pingResponse.getStatus() == 0 ? HttpServletResponse.SC_OK : HttpServletResponse.SC_SERVICE_UNAVAILABLE,
                    "\"data\":" + pingResponse.getMessage());
        } catch (final Exception e) {
            if (logger.isDebugEnabled()) {
                logger.debug("Failed to process a ping request.", e);
            }

    )
    val openAtNanos = System.nanoTime()
    newWebSocket()
    clientListener.assertOpen()
    clientListener.assertFailure(
      SocketTimeoutException::class.java,
      "sent ping but didn't receive pong within 500ms (after 0 successful ping/pongs)",
    )
    latch.countDown()
    val elapsedUntilFailure = System.nanoTime() - openAtNanos
    assertThat(TimeUnit.NANOSECONDS.toMillis(elapsedUntilFailure).toDouble())

    assertThat(response.protocol).isEqualTo(protocol)

    // Confirm a single ping was sent and received, and its reply was sent and received.
    val logs = testLogHandler.takeAll()
    assertThat(countFrames(logs, "FINE: >> 0x00000000     8 PING          "))
      .isEqualTo(1)
    assertThat(countFrames(logs, "FINE: << 0x00000000     8 PING          "))
      .isEqualTo(1)

    }
  }

  @Test fun emptyPingCallsCallback() {
    data.write("8900".decodeHex()) // Empty ping
    clientReader.processNextFrame()
    callback.assertPing(EMPTY)
  }

  @Test fun pingCallsCallback() {
    data.write("890548656c6c6f".decodeHex()) // Ping with "Hello"
    clientReader.processNextFrame()
    callback.assertPing("Hello".encodeUtf8())
  }

     * Sets the interval between HTTP/2 and web socket pings initiated by this client. Use this to
     * automatically send ping frames until either the connection fails or it is closed. This keeps
     * the connection alive and may detect connectivity failures.
     *
     * If the server does not respond to each ping with a pong within `interval`, this client will

        });

    }

    /**
     * Pings the search engine cluster to check connectivity and health.
     *
     * @return the ping response with cluster information
     * @throws SearchEngineClientException if the ping fails
     */
    public PingResponse ping() {
        try {
            final ClusterHealthResponse response =

# Whether to allow credentials for CORS.
api.cors.allow.credentials=true
# Whether to enable JSONP for API.
api.jsonp.enabled=false
# Fields for API ping to search engine.
api.ping.search_engine.fields=status,timed_out


# Virtual Host: Host:fess.codelibs.org=fess
virtual.host.headers=

# Hostname for the HTTP proxy server.
http.proxy.host=

     */
    boolean isApiJsonpEnabled();

    /**
     * Get the value for the key 'api.ping.search_engine.fields'. <br>
     * The value is, e.g. status,timed_out <br>
     * comment: Fields for API ping to search engine.
     * @return The value of found property. (NotNull: if not found, exception but basically no way)
     */