kaa - 如何从应用程序检测端点(KAA SDK)是否连接到 KAA 服务器的天气

Question

是否有任何机制或方法或步骤来检测从应用程序到 KAA 服务器的端点(KAA SDK)连接。

如果不是，那么我们如何通过远程识别故障设备？或者我们如何识别在现场部署设备后无法与 KAA 服务器通信的设备？

如何实现这一要求以释放物联网的力量？？

Answer 1

如果您的端点在连接到 Kaa 服务器时遇到一些问题，则会发生“故障转移”。

所以你必须定义你自己的故障转移策略并为你的 Kaa 客户端设置它。每次发生故障转移策略的 onFialover()方法将被调用。

您可以在下面看到 Java SDK 的代码示例。

  import org.kaaproject.kaa.client.DesktopKaaPlatformContext;
  import org.kaaproject.kaa.client.Kaa;
  import org.kaaproject.kaa.client.KaaClient;
  import org.kaaproject.kaa.client.SimpleKaaClientStateListener;
  import org.kaaproject.kaa.client.channel.failover.FailoverDecision;
  import org.kaaproject.kaa.client.channel.failover.FailoverStatus;
  import org.kaaproject.kaa.client.channel.failover.strategies.DefaultFailoverStrategy;
  import org.kaaproject.kaa.client.exceptions.KaaRuntimeException;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;

  import java.io.IOException;
  import java.util.concurrent.TimeUnit;

  /**
  * A demo application that shows how to use the Kaa credentials API.
  */
  public class CredentialsDemo {
  private static final Logger LOG = LoggerFactory.getLogger(CredentialsDemo.class);
  private static KaaClient kaaClient;

  public static void main(String[] args) throws InterruptedException, IOException {

  LOG.info("Demo application started");

  try {

  // Create a Kaa client and add a startup listener
  kaaClient = Kaa.newClient(new DesktopKaaPlatformContext(), new SimpleKaaClientStateListener() {
  @Override
  public void onStarted() {
  super.onStarted();
  LOG.info("Kaa client started");
  }
  }, true);

  kaaClient.setFailoverStrategy(new CustomFailoverStrategy());
  kaaClient.start();

  // ... Do some work ...

  LOG.info("Stopping application.");
  kaaClient.stop();

  } catch (KaaRuntimeException e) {
  LOG.info("Cannot connect to server - no credentials found.");
  LOG.info("Stopping application.");
  }

  }

  // Give a possibility to manage device behavior when it loses connection
  // or has other problems dealing with Kaa server.
  private static class CustomFailoverStrategy extends DefaultFailoverStrategy {

  @Override
  public FailoverDecision onFailover(FailoverStatus failoverStatus) {
  LOG.info("Failover happen. Failover type: " + failoverStatus);

  // See enum DefaultFailoverStrategy from package org.kaaproject.kaa.client.channel.failover
  // to list all possible values
  switch (failoverStatus) {
  case CURRENT_BOOTSTRAP_SERVER_NA:
  LOG.info("Current Bootstrap server is not available. Trying connect to another one.");

  // ... Do some recovery, send notification messages, etc. ...

  // Trying to connect to another bootstrap node one-by-one every 5 seconds
  return new FailoverDecision(FailoverDecision.FailoverAction.USE_NEXT_BOOTSTRAP, 5L, TimeUnit.SECONDS);
  default:
  return super.onFailover(failoverStatus);
  }
  }
  }
  }

更新 (2016/10/28)

来自 服务器端您可以检查端点凭据状态，如方法 checkCredentialsStatus() 中所示在下面的代码中。状态 IN_USE显示端点至少有一次成功的连接尝试。

不幸的是，在当前的 Kaa 版本中，无法直接检查端点是否连接到服务器。我在代码示例之后描述它们。

  package org.kaaproject.kaa.examples.credentials.kaa;

  import org.kaaproject.kaa.common.dto.ApplicationDto;
  import org.kaaproject.kaa.common.dto.admin.AuthResultDto;
  import org.kaaproject.kaa.common.dto.credentials.CredentialsStatus;
  import org.kaaproject.kaa.examples.credentials.utils.IOUtils;
  import org.kaaproject.kaa.server.common.admin.AdminClient;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;

  import java.util.List;

  public class KaaAdminManager {

  private static final Logger LOG = LoggerFactory.getLogger(KaaAdminManager.class);

  private static final int DEFAULT_KAA_PORT = 8080;
  private static final String APPLICATION_NAME = "Credentials demo";

  public String tenantAdminUsername = "admin";
  public String tenantAdminPassword = "admin123";

  private AdminClient adminClient;

  public KaaAdminManager(String sandboxIp) {
  this.adminClient = new AdminClient(sandboxIp, DEFAULT_KAA_PORT);
  }

  // ...

  /**
  * Check credentials status for getting information
  * @return credential status
  */
  public void checkCredentialsStatus() {
  LOG.info("Enter endpoint ID:");

  // Reads endpoint ID (aka "endpoint key hash") from user input
  String endpointId = IOUtils.getUserInput().trim();

  LOG.info("Getting credentials status...");
  try {
  ApplicationDto app = getApplicationByName(APPLICATION_NAME);
  String appToken = app.getApplicationToken();

  // CredentialsStatus can be: AVAILABLE, IN_USE, REVOKED
  // if endpoint is not found on Kaa server, exception will be thrown
  CredentialsStatus status = adminClient.getCredentialsStatus(appToken, endpointId);
  LOG.info("Credentials for endpoint ID = {} are now in status: {}", endpointId, status.toString());
  } catch (Exception e) {
  LOG.error("Get credentials status for endpoint ID = {} failed. Error: {}", endpointId, e.getMessage());
  }
  }

  /**
  * Get application object by specified application name
  */
  private ApplicationDto getApplicationByName(String applicationName) {
  checkAuthorizationAndLogin();

  try {
  List<ApplicationDto> applications = adminClient.getApplications();
  for (ApplicationDto application : applications) {
  if (application.getName().trim().equals(applicationName)) {
  return application;
  }
  }
  } catch (Exception e) {
  LOG.error("Exception has occurred: " + e.getMessage());
  }
  return null;
  }

  /**
  * Checks authorization and log in
  */
  private void checkAuthorizationAndLogin() {
  if (!checkAuth()) {
  adminClient.login(tenantAdminUsername, tenantAdminPassword);
  }
  }

  /**
  * Do authorization check
  * @return true if user is authorized, false otherwise
  */
  private boolean checkAuth() {
  AuthResultDto.Result authResult = null;
  try {
  authResult = adminClient.checkAuth().getAuthResult();
  } catch (Exception e) {
  LOG.error("Exception has occurred: " + e.getMessage());
  }
  return authResult == AuthResultDto.Result.OK;
  }

  }

您可以看到更多使用 AdminClient 的示例。在类 KaaAdminManager在 Credentials Demo Application来自 Kaa sample-apps project在 GitHub 上。

了解解决方法

使用 Kaa Notifications结合 Kaa Data Collection特征。服务器向端点发送特定的单播通知(使用端点 ID)，然后端点回复使用数据收集功能发送数据。服务器稍等片刻，然后检查端点的最后一个 appender 记录(通常在数据库中)的时间戳(通过端点 ID)。所有消息都是异步发送的，因此您必须根据您的实际环境选择响应等待时间。

使用 Kaa Data Collection功能而已。这种方法更简单，但有一定的性能缺陷。如果您的端点必须根据其性质(测量传感器等)向 Kaa 服务器发送数据，您可以使用它。端点只是定期向服务器发送数据。当服务器需要检查端点是否“在线”时，它查询保存的数据日志(通常是数据库)以通过端点 ID( key 哈希)获取最后一条记录并分析时间戳字段。

* 有效利用 Kaa Data Collection功能，您必须在所选日志附加程序的设置中添加此类元数据(在 Kaa Admin UI 中):“端点键哈希”(与“端点 ID”相同)、“时间戳”。这将自动向从端点接收的每个日志记录添加所需的字段。