The active health monitor is used to test whether a server is available. The active health monitor uses several types of tests such as sending a basic ping to servers or advanced HTTP requests to monitor application health.

Servers that fail to respond within a certain time period or respond with errors are excluded from future connection handling until a subsequent periodic health check finds these servers to be healthy.

Active health checks are performed on server pool members after the pool member is attached to a virtual server and that virtual server is attached to a tier-1 logical router. The tier-1 uplink IP address is used for the health check.

Note: One active health monitor can be configured per server pool.

Procedure

  1. From your browser, log in with admin privileges to an NSX Manager at https://nsx-manager-ip-address.
  2. Select Load Balancer > Networking > Monitors > Active Health Monitors > Add.
  3. Enter a name and description for the active health monitor.
  4. Select a health check protocol for the server from the drop-down menu.
    You can also use predefined protocols in NSX Manager; http-monitor, https-monitor, Icmp-monitor, Tcp-monitor, and Udp-monitor.
  5. Set the value of the monitoring port.
  6. Configure the values to monitor a service pool.
    You can also accept the default active health monitor values.
    Option Description
    Monitoring Interval Set the time in seconds that the monitor sends another connection request to the server.
    Fall Count Set a value when the consecutive failures reach this value, the server is considered temporarily unavailable.
    Rise Count Set a number after this timeout period, the server is tried again for a new connection to see if it is available.
    Timeout Period Set the number of times the server is tested before it is considered as DOWN.
    For example, if the monitoring interval is set as 5 seconds and the timeout as 15 seconds, the load balancer send requests to the server every 5 seconds. In each probe, if the expected response is received from the server within 15 seconds, then the health check result is OK. If not, then the result is CRITICAL. If the recent three health check results are all UP, the server is considered as UP.
  7. If you select HTTP as the health check protocol, complete the following details.
    Option Description
    HTTP Method Select the method to detect server status from the drop-down menu, GET, OPTIONS, POST, HEAD, and PUT.
    HTTP Request URL Enter the request URI for the method.
    HTTP Request Version Select the supported request version from the drop-down menu.

    You can also accept the default version, HTTP_VERSION_1_1.

    HTTP Request Body Enter the request body.

    Valid for the POST and PUT methods.

    HTTP Response Code Enter the string that the monitor expects to match in the status line of HTTP response body.

    The response code is a comma-separated list.

    For example, 200,301,302,401.

    HTTP Response Body If the HTTP response body string and the HTTP health check response body match, then the server is considered as healthy.
  8. If you select HTTPs as the health check protocol, complete the following details.
    1. Select the SSL protocol list.
      TLS versions TLS1.1 and TLS1.2 versions are supported and enabled by default. TLS1.0 is supported, but disabled by default.
    2. Click the arrow and move the protocols into the selected section.
    3. Assign a default SSL cipher or create a custom SSL cipher.
    4. Complete the following details for HTTP as the health check protocol.
      Option Description
      HTTP Method Select the method to detect server status from the drop-down menu, GET, OPTIONS, POST, HEAD, and PUT.
      HTTP Request URL Enter the request URI for the method.
      HTTP Request Version Select the supported request version from the drop-down menu.

      You can also accept the default version, HTTP_VERSION_1_1.

      HTTP Request Body Enter the request body.

      Valid for the POST and PUT methods.

      HTTP Response Code Enter the string that the monitor expects to match in the status line of HTTP response body.

      The response code is a comma-separated list.

      For example, 200,301,302,401.

      HTTP Response Body If the HTTP response body string and the HTTP health check response body match, then the server is considered as healthy.
  9. If you select ICMP as the health check protocol, assign the data size in byte of the ICMP health check packet.
  10. If you select TCP as the health check protocol, you can leave the parameters empty.
    If both the sent and expected are not listed, then a three-way handshake TCP connection is established to validate server health. No data is sent. Expected data if listed has to be a string and can be anywhere in the response. Regular expressions are not supported.
  11. If you select UDP as the health check protocol, complete the following required details.
    Required Option Description
    UDP Data Sent Enter the string to be sent to a server after a connection is established.
    UDP Data Expected Enter the string expected to receive from the server.

    Only when the received string matches this definition, is the server is considered as UP.

  12. Click Finish.

What to do next

Associate the active health monitor with a server pool. See Add a Server Pool for Load Balancing.