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Tom_K_185554's avatar
Tom_K_185554
Icon for Nimbostratus rankNimbostratus
Oct 31, 2018

What will happen if no members in a high speed logging pool are available ?

I have an irule that sends tcp event data, client_accepted, client_closed, server_connected and server_closed to splunk using hsl high speed logging. My question is what will happen to ongoing connec...
application delivery
iRules
LTM
Hamish's avatar
Hamish
Icon for Cirrocumulus rankCirrocumulus
Nov 02, 2018

Yes. There are differences between UDP and TCP.

 

With UDP logging it's fire & forget. Send a message == send a UDP packet. The messages arrive out of order and aren't guaranteed to arrive.

 

TCP logging on the other hand uses a stream. Messages WITHIN a TCP dream arrive in order. but when you have >1 tcp stream (Which you do as soon as HSL doesn't have a free connection) HSL will open a new tcp connection. Then messages arrive out of order ACROSS the connections.

 

Neither is always useful under stress.

 

I ran into issues many years ago with HSL. It's been a while since I destructively tested HSL, but the way it worked with TCP, is that IF there is an open and idle connection to a pool member, it'll be used. if not, a new one will be opened. There was pretty much no control over what happened. I even got to the point where we ran out of ports during stress testing...

 

As I was more interested in numbers (i.e. numbers of connections & messages I ended up doing the counting in an iRule and then sending the contents of the stats table from the BigIP to the backend servers on a timer. YMMV.