[ClusterLabs] Establishing Timeouts

[Christine Caulfield]

On 10/10/16 05:51, Eric Robinson wrote:
> I have about a dozen corosync+pacemaker clusters and I am just now getting around to understanding timeouts.
> 
> Most of my corosync.conf files look something like this:
> 
>         version:        2
>         token:          5000
>         token_retransmits_before_loss_const: 10
>         join:           1000
>         consensus:      7500
>         vsftype:        none
>         max_messages:   20
>         secauth:        off
>         threads:        0
>         clear_node_high_bit: yes
>         rrp_mode: active
> 
> If I understand this correctly, this means the node will wait 50 seconds (5000ms x 10) before deciding that a cluster reconfig is necessary (perhaps after a link failure). Is that correct?
> 

No that's not correct. the token timeout is 5 seconds in your example -
because token is 5000mS. the token timeout is always what the value of
totem.token is.

token_retransmits_before_loss_const affects the token hold timeout -
which is how long the token is held on a node that has no messages to
send before being forwarded on. So increasing
token_retransmits_before_loss_const changes the number of times per
'token' timeout that the token is actually sent.

In the example above you will see that the token is sent approximately
5000/10 = 500 mS. That's approximate, the value is scaled slightly to
make actual timeouts less likely, and also is affected by messages that
may beed to be sent.

Chrissie

> I'm trying to understand how this works together with my bonded NIC's arp_interval settings. I normally set arp_interval=1000. My question is, how many arp losses are required before the bonding driver decides to failover to the other link? If arp_interval=1000, how many times does the driver send an arp and fail to receive a reply before it decides that the link is dead?
> 
> I think I need to know this so I can set my corosync.conf settings correctly to avoid "false positive" cluster failovers. In other words, if there is a link or switch failure, I want to make sure that the cluster allows plenty of time for link communication to recover before deciding that a node has actually died. 
> 
> --
> Eric Robinson
> 
> 
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