Troubleshooting alerts

  • Last updated on: 2016-10-28
  • Authored by: Susan Million

When a monitoring check reaches or passes a specific threshold or value, an alert is triggered and you receive a Warning or Critical email notification for the monitored resource. This article describes some simple troubleshooting steps that can help you diagnose the problem.

Ping checks

Ping checks typically monitor a server. If your ping check triggers an alert immediately try to contact your server by using the ping command.

Issue the following command from an OS X Terminal window, Windows Command Prompt, or a Linux shell:

ping <targetHostnameorIpaddress>

If the host returns a result of O packets received, you might be experiencing network connection issues. Use the traceroute networking to diagnose any network issues. For more information about using ping and traceroute for network troubleshooting, see Common network troubleshooting tools.

HTTP checks

HTTPs check are used to check websites. If you receive a notification from an HTTP check, try the following preliminary troubleshooting steps:

  1. Open the website in a browser to verify that the website is actually responding.

  2. If you are checking for specific content with a body match, verify that the content of the body match actually exists on the page that you are viewing.

    Your browser returns the page or it might return another error saying that the site was unreachable or an error code from the web server. Following are common error codes:

    • 404, which means that the page was not found
    • 503, which means that the web server is denying access to the content that you are trying to view

Advanced troubleshooting for HTTP checks

Run cURL, a common command-line web page utility, against the website that you are checking to return the contents of the web page to your terminal or shell window. You can explore cURL’s options to get more specific information, but a useful option is -I. This option returns the target web page’s headers and the response code from the web server.

For example, enter the following command in your terminal or shell window, replacing yourDomain with your actual domain:

curl -I http://www.yourDomain.com

The output should look something like this:

HTTP/1.1 200 OK
Content-Type: text/html; charset=UTF-8
Last-Modified: Tue, 04 Sep 2012 20:00:05 GMT
P3P: CP="ALL DSP COR CUR ADMo DEVo TAIo PSAo PSDo IVAo CONi OTPi OUR NOR UNI"
Server: Apache Date: Tue, 04 Sep 2012 20:33:51 GMT
Connection: keep-alive Set-Cookie: target=us; path=/; domain=.your_domain.com Expires: Tue, 04 Sep 2012 21:00:00 GMT

TCP checks

TCP checks monitor ports. If an alert is triggered for a TCP check, use Telnet to try to communicate with the target or scan your target for the open port.

Note: Ensure that you are authorized to scan the target. Many network security groups view this type of scan as an attack on the open port.

Alternatively, try to directly access the service that is running on that port. For example, if the service is an SSH server, try to open an ssh session to the target host. If the service is running MySQL or Microsoft SQL Server, try to connect to the database.

Following is an example of how to use Telnet to communicate with the default port (3306) for MySQL:

telnet mysql.myhost.com 3306

To exit Telnet, type Ctrl \], press the Enter key, and then type quit.

Other resources

If you’re unable to solve the problem by using the steps outlined in this article, review the information in the following documents:

If you need more assistance, contact Rackspace Support.

Continue the conversation in the Rackspace Community.