topic Re: Ace probe failure after IIS app pool recycle? in Application Networking

Ace probe failure after IIS app pool recycle?

dan.worstell — Wed, 14 Apr 2010 20:02:09 GMT

Windows Server 2003 SP2

ACE Module A2(1.6a)

I suspect this is caused by an IIS6 setting, but posting here in case anyone has seen this. For this one particular site, we have 4 servers in the farm. 2 of those servers are fine. The other 2 (new) servers will generate probe failure after the site's app pool recycles. I then remove the 2 servers from service and re-activate (no inservice, then inservice) and the probe comes back as operational. It appears that the app pool recycle somehow is resetting the hash on the default page, though I'm not sure how. Any ideas are very much appreciated.

Re: Ace probe failure after IIS app pool recycle?

Marko Leopold — Thu, 15 Apr 2010 06:53:17 GMT

Do you use the hash command inside the probe? Can you provide configuration?

Re: Ace probe failure after IIS app pool recycle?

dan.worstell — Thu, 15 Apr 2010 12:54:27 GMT

Yeah, the hash is inside the probe. Here's the config for the serverfarm and the probe. Public-007 and Public-008 are new servers...the other 6 have been in the farm for the last 2.5 years and they don't have this issue. It's only the 2 new boxes that the probe fails when the app pool is recycled.

serverfarm host PUBLIC
probe URL-DEFAULT-ASPX
rserver PUBLIC-001
    inservice
rserver PUBLIC-002
    inservice
rserver PUBLIC-003
    inservice
rserver PUBLIC-004
    inservice
rserver PUBLIC-005
    inservice
rserver PUBLIC-006
    inservice
rserver PUBLIC-007
    inservice
rserver PUBLIC-008
    inservice


probe http URL-DEFAULT-ASPX
interval 2
faildetect 2
passdetect interval 2
passdetect count 2
request method get url /default.aspx
expect status 200 200
hash

Re: Ace probe failure after IIS app pool recycle?

Marko Leopold — Thu, 15 Apr 2010 13:29:21 GMT

Hello Dan!

We ran into same issue here. The documentation says that the ACE is taking the hash from the site that it gets from the server. So far so good, but if this hash is changing the server is marked offline. Problem is, I did not found any coomand to display this hash. Even the "show probe XXX detail" dont show anything. The old CSS was able to show the hash value so you can check it. Question the the crowd: Which command shows me the hash value of the probe?

Maybe you should check if the 2 new server are changing something in the website (maybe something in header) which is sent after the app pool is recycled!

Re: Ace probe failure after IIS app pool recycle?

dan.worstell — Thu, 15 Apr 2010 13:39:11 GMT

I do believe something is different on the 2 new boxes, but have not yet found what it is. I just found this in the iis

log. The app pool recycled at 23:30:11 and we started getting different response from the web server when hitting the default page. I think this confirms the hash change....

2010-04-14 23:30:07 10.1.1.1 GET /default.aspx - 80 - 10.1.2.2 - 200 0 0
2010-04-14 23:30:09 10.1.1.1 GET /default.aspx - 80 - 10.1.2.1 - 200 0 0
2010-04-14 23:30:09 10.1.1.1 GET /default.aspx - 80 - 10.1.2.2 - 200 0 0
2010-04-14 23:30:11 10.1.1.1 GET /default.aspx - 80 - 10.1.2.1 - 200 0 0
2010-04-14 23:30:12 10.1.1.1 GET /default.aspx - 80 - 10.1.2.2 - 200 0 64
2010-04-14 23:30:13 10.1.1.1 GET /default.aspx - 80 - 10.1.2.1 - 200 0 64
2010-04-14 23:30:13 10.1.1.1 GET /default.aspx - 80 - 10.1.2.2 - 200 0 64
2010-04-14 23:30:15 10.1.1.1 GET /default.aspx - 80 - 10.1.2.1 - 200 0 64

Re: Ace probe failure after IIS app pool recycle?

dan.worstell — Thu, 15 Apr 2010 14:50:14 GMT

I found a utility called simplemd5 that reads the hash for us. More perplexing is the hash value is the same for the file regardless if the probe has failed or not:

C:\Users\User\Desktop>simplemd5 default.aspx
F2CA9290F11E5DCF2BE0DED2A675AA1C

Re: Ace probe failure after IIS app pool recycle?

Marko Leopold — Thu, 15 Apr 2010 16:07:38 GMT

mmm strange. but what means the 64 in your last message?

Re: Ace probe failure after IIS app pool recycle?

dan.worstell — Thu, 15 Apr 2010 20:31:37 GMT

We figured it out. You have to edit the machine.config to support a load balanced environment. We had already done that for .Net 2.0, but this was the only site running .Net 1.1 on these 2 new boxes. We hadn't edited 1.1 yet.