Health Check Question

Hi Greg,

 

 

You can have the BIG-IP tell the server that the server close the TCP connection using an HTTP 1.1 formatted send string with a Connection header:

 

 

GET /monitor_page.html HTTP/1.1\r\nHost: \r\nConnection: Close\r\n

 

 

Sessions would be created on the application--not LTM. If you want to tell the server that the session should be removed, you'd need to figure out how the client can do that in an HTTP request and then configure that in the SEND string. If it requires two requests (one to create the session and one to close it) you could create an external monitor which references a shell script to make the two requests. You can find some examples for external monitors in the Monitoring Codeshare (Click here). Else, is there a page which LTM could monitor for which the server won't generate a session? That might be easier than trying to end the session.

 

 

Aaron

Aaron,

 

 

Thank you for the information. My apologies on the delayed response. In reading your response, it looks like there are two possible options. One would be to create my own custom monitor on the LTM or the second to find or write an external script. If I might pursue the first, since all I want is a simple get and then terminate the session can ask a few more questions then?

 

 

My LTM currentl manages about 10 pools each with their own application environment.. basically each environment has a unique port.For each pool I am doing an HTTP health test.

 

 

1) Does that mean, on the LTM I would have create a custom HTTP health monitor for each pool?

 

2) Do you happen to know of any sample snippets of something similar I could use for reference? Iask because when I look at the snippet you provided I am not sure if that is the exact string? or do I substitute a real HTML page, host, connection port into that string?

 

 

 

thanks

 

Greg

 

thanks

 

Greg

Hi Greg,

 

 

Most webservers will respond to a request with an HTTP host header and no value. The Connection: close header tells the server that the client won't try to re-use the TCP connection, so the server can close the connection after responding to the request.

 

 

Rather than worrying about the monitor configuration, I'd focus first on finding a page you can make a request to where the server doesn't generate a session. If that's possible, you could use a standard HTTP monitor with a customized send string. If that's not possible, then you could figure out how to make a request which tells the server to kill the session. That would probably take two requests and require using an external monitor which references a shell script using curl. There are examples of using curl from a shell script for an external monitor in the monitoring Codeshare (Click here).

 

 

Aaron

Hi aaraon

 

 

is that possible use http monitor for text content

 

for example i want send request GET /id/123445 and receive string hello

 

but hello content in the text file not html

 

this is not working with this way

 

i also use this method getting response from html content

 

 

is that possible work from text file

 

 

 

regards

 

 

zafer

Hi zafer,

 

 

The monitoring daemon evaluates the receive string against the response content. So it shouldn't matter what type of file you configure for the request as long as the server responds with the expected content.

 

 

If this isn't working, you could either enable bigd debug (b db bigd.debug enable) and check the /var/log/bigdlog file, or you could test from the command line using curl. If you make a curl request from LTM to a pool member, do you get back a response containing "hello"? You can use something like 'curl -v http://1.1.1.1/id/123445' to test where 1.1.1.1 is the pool member IP address.

 

 

Aaron

 

Aaron,

 

 

I am truly appreciative of your assistance on this issue and I feel bad about my lack of knowledge on these types of resolutions. I confess I am not an HTTP guru and recently inherited the F5 management so I will apologize if these questions are remedial. I have been re-reading your responses and I think I understand but I need to delve a little deeper to understand. I am providing more information on my environment in hopes to better understand your suggestions.

 

 

My configuration as such is that I have 4 physical web servers running multiple application environments on each server via a unique port number. I have created a pool for each application environment as dictated specify the unique port number for that pool. For example, I have a test environment running on port 80 and a training environment running on port 8080 with Websphere as my App/Web server.

 

 

train_pool conains webserver1 & webserver2 port 8080

 

test_pool contains webserver3 & webserver4 --port 80

 

 

When creating the pool I use the default Health Check to test if Webserver is available. I also have standard log in Page for each environment and use IRULES for URI filter.. for example

 

 

www.domain.com/train/jsp/pgLogin.jsp (which is directed to train_pool and port)

 

www.domain.com/test/jsp/pgLogin.jsp (which is directed to test_pool and port)

 

 

 

With this default configuration, I know the F5 performs an HTTP GET as its health check for the pool, and I assume for each physical server in the pool. This health check seems to create a session but not terminate it.. I know on the F5 you can create custom HTTP, as you indicated. What I did not understand was that there is some HTTP GET string I can create for Send strings that would be able to HTTP GET and then terminate/close the session. Is that correct? Do I put a custom receive string?I am not sure I understand the recieve string section and trying to find the Syntax... Below is a sample string I was thinking for say the train environment

 

 

 

GET /train HTTP/1.1\r\nHost: \r\nConnection: Close\r\n

 

 

 

Is this all I need with no receive string? I am assuming that the "Host" and "Connection" pieces are populated automatically via the F5 request. is it possible you can shed a little more light

 

 

thank you for help

 

Greg

 

 

Hi Aaron,

 

when i request the webpage from browser it works i think browser converting text to html

 

but when i use curl request the page i see 500 internal server error

 

 

what can i do monitor from flat file

 

 

zafer

 

Hi Aaron

 

i think problem is the ISS, it only accepts get request from IE and Mozilla

 

 

ISS works between client and webserver for protect from attacks

 

 

 

regards

 

zafer