Does Persistence Override Availability?

[Joseph Mack NA3T]

On Tue, 15 May 2007, Robinson, Eric wrote:

> We turned off one of the servers and now it looks like this, which is
> expected:

how did you turn off the server? set the weight to 0? power 
down the server?


> [root at lb1 ]# ipvsadm|grep 3008
> TCP  extrovert.mydomain.com:3008 lblc persistent 360
>  -> appftp2.mydomain.com:3008     Masq    0      0          3
>  -> appftp1.mydomain.com:3008     Masq    1      2          6
>
>
> However, users who were connected to appftp2 got "page could not be
> displayed" errors, which tells me that LVS is was still directing
> traffic to the down server.

the expected result of using persistence.

> After a while, the situation cleared up. I assume this is because
> ipvsadm started directing traffic to the up server.

well yes, but only because clients no longer had connections 
open to appftp2

> Does anyone know why this would be happening? Is my persistent=360
> statement causing ipvsadm to ignore the down state of the realserver?

persistence doesn't care whether the realserver is there or 
not (neither does ipvsadm). If you use persistence, you are 
guaranteeing to the client that the realserver will be there 
for 360 sec after the last client has closed their 
connection.

If you just want a client to always go to the same 
realserver, try the -SH scheduler.

Joe

-- 
Joseph Mack NA3T EME(B,D), FM05lw North Carolina
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