Global value and wideip

Thank you Yoann.

 

My requirement is very similar to following post.

 

https://devcentral.f5.com/s/articles/single-node-persistence

 

The requirement is that DNS queries direct to only a single node in a pool.

 

1. Initially, traffic should always go to node A.
2. If Node A fails by monitor down, then traffic will go to Node B.
3. When Node A comes back online, traffic should continue to go to Node B.
4. When Node B fails, then the traffic should go to Node A.

Our system is not allowed to use "Global Availability", because Node A recovers from fails, DNS queries return back to Node A from Node B.

 

               Node A(Down) Order 0
 DNS query ==> Node B(Up) Order 1

 DNS query ==> Node A(Up) Order 0
               Node A(Up) Order 1

So, I tried to put following irule, which has been introduced in the post, into my BIG-IP DNS.

 

when DNS_REQUEST { 
     persist uie 1 
}

It seems to work expectedly. But I've hesitated to apply it due to Michael Gilin's comment.

 

Using "persist uie 1" iRule is not recommended,

So, I came up with another idea like this. just an idea. How I think is that memorize whether a query is distributed NodeA or NodeB, and then when next query comes, checking flag to confirm which node the previous query was distributed. When a newly DNS query comes, newly DNS query would continue to send to the same node along with the content of the flag table. But it can't use a table.

 

when DNS_REQUEST {
.

.

    if { { NodeA eq "up" } && { [table lookup flag] eq "01"} } {
        pool NodeA
        table set flag "01"
    } else if { { NodeB eq "up" } && { [table lookup flag] eq "10"} } {
        pool NodesB
        table set flag "10"
    }
}