Rebalancing connections

[miljans]

Hi,

I have a question about connections to the pool memebers.

In the event of the failure of one of the pool memebers the connections will be established on the available member.

When the failed member comes back online can the connections be transfered back to that member so that the load is balanced again?

[mihaic]

it depends on the load-balancing method you use.

You probably want the least-connections method. But the connections are not transferred back. New connections will be sent to the  member that has the least number of current connections in the pool

here are the methods:

https://support.f5.com/csp/article/K42275060

[Seçkin1983]

F5 will reap all connections about this pool member if your pool member is monitor down and it will reset the connection for both sides client and server. The connections will be re-established with the available pool member as a new independent connection. When failed member comes back online, F5 do not send the all client traffic immediately instead will send new connections gradually.

[Hooni_L]

Hi,

Traffic is forwarded to the available server for new connections only.

but, If used persistence profile, It not come back Client connection when have persist and connection table.

@Seçkin1983 said

'F5 do not send the all client traffic immediately instead will send new connections gradually'

--> options is 'Slow Ramp Time '

Slow Ramp Time

Specifies the duration during which the system sends less traffic to a newly-enabled pool member. The amount of traffic is based on the ratio of how long the pool member has been available compared to the slow ramp time, in seconds. Once the pool member has been online for a time greater than the slow ramp time, the pool member receives a full proportion of the incoming traffic. Slow ramp time is particularly useful for the least connections load balancing mode

Setting this to a nonzero value can cause unexpected Priority Group behavior, such as load balancing to a low-priority member even with enough high-priority servers.

[miljans]

Hi guys, thanks for the quick reply.

As I suspected, only the new connections will be sent to the newly available server. We have Least Connections (Member) for the Load Balancing Method.

@Hooni_L if I understand you correctly the connections will not be transfered the the available member if persistance profile is used?

[Seçkin1983]

if monitor down happens, all connections including persisted and existing will be resetted on both sides client and server connected. 

[Hooni_L]

@miljans 

I known if you need transfer the available member when persist enable and going down pool member, you setting 'action on service down value reject' on pool.

Action on service down Reject

Send a deny to the client and server when the connection table exists and the pool member goes down.

[mihaic]

you might want to use Reselect on the pool Action on Service down. But it applies only in certain scenarios.

Read about it first. Otherwise, the Reject option looks to be better.

Have a look here:

https://support.f5.com/csp/article/K15095

[miljans · Accepted solution]

Thanks guys! 

Basically there is no option to transfer already established connections to the new pool member.