HTTP monitoring from a shared server

I will try to explain with a draw .... sorry, I am not good on this

OPTION 1

site1 ---|                                          | ---> ServerA
site2 ---| ---> IP 1.1.1.1 (F5) ---> | ---> ServerB
site3 ---|                                          | ---> ServerC

Heath Check
GET /health/index.html HTTP/1.1\r\n
Host: health
Connection: close\r\n

OPTION 2

                                     | ---> ServerA
site1 ---| ---> IP 1.1.1.1 (F5) ---> | ---> ServerB
                                     | ---> ServerC
Heath Check
GET /health/index.html HTTP/1.1\r\n
Host: site1\r\n
Connection: close\r\n
                                     | ---> ServerA
site2 ---| ---> IP 1.1.1.2 (F5) ---> | ---> ServerB
                                     | ---> ServerC
Heath Check
GET /health/index.html HTTP/1.1\r\n
Host: site2r\n
Connection: close\r\n
                                     | ---> ServerA
site3 ---| ---> IP 1.1.1.3 (F5) ---> | ---> ServerB
                                     | ---> ServerC
Heath Check
GET /health/index.html HTTP/1.1\r\n
Host: site3\r\n
Connection: close\r\n

You can do the same type of HOST header redirection on the BIG-IP that you're doing on the original (multi-site) server using a single external listener IP. This can be achieved with an HTTP class or an iRule, but easier to show what I mean with an iRule example:

1 VIP (1 IP and port)

3 DNS entries pointing to the same VIP IP

3 pools (one for each site) - application-specific monitor applied to each pool

1 iRule:

when HTTP_REQUEST {
     switch [string tolower [HTTP::host]] {
          "site1.domain.com" { pool site1_pool }
          "site2.domain.com" { pool site2_pool }
          "site3.domain.com" { pool site3_pool }
          default { drop }
     }
}

Hello Kevin, thank you for you reply.

 

As I told you, I am new with F5, just to see if I understand correct.

 

 

Will this iRule be applied on all pools or applied as general on the F5 for all requests?

 

Because there are other pools that should not be in this rule, but need to work as normal VIP and pool.

This iRule is only applied to the VIP that supports multiple sites/pools under a single external listener IP.

Thank you again.

 

 

Nice, so VIP will receive the request and this iRule will decide to which pool the request will use.

 

Each pool will have its own monitor and each one will evaluate if this site is alive or not.

 

 

Thank you so much.

Hi Kevin, one more question.

 

 

Is there any way to create an iRule like below? (It is a fake code)

 

So, with some iRule like that, I do not need to change the iRule on every new site.

 

 

when HTTP_REQUEST {
     var host = [string tolower [HTTP::host]]
     pool $host_pool
}

 

 

Thank you

It is definitely possible, assuming 2 things:

1. There's a pool named or that can be derived from the requested host name, and

2. You should check to make sure the pool exists before trying to use it.

set pool [string tolower [HTTP::host]]_pool

or

set host [string tolower [HTTP::host]]
set pool ${host}_pool

if { [catch { 
     pool $pool
}] } {
      Send to default pool and log error
     log local0. "Requested pool ($pool) doesn't exist"
}

Hi Kevin, how are you? I hope you are fine.

 

It has been a long time, but just to let you know that I tested it on our environment and it worked perfectly.

 

 

Thank you so much.