[Mongrel] Problems monitoring Mongrel with F5 BigIP

Christopher Bailey chris at codeintensity.com
Fri Aug 10 19:45:34 EDT 2007

If this has already been covered, please point me to that (I didn't find
anything in my searches)...

We are using F5 BigIP LTM load balancers.  They have many pools of Mongrels
they load balance across, and I of course want the F5 to know when a Mongrel
goes down or is unavailable, etc.  To do that, I need to have an F5 health
monitor for HTTP make a request to the Mongrel.  We do this same thing with
our Nginx servers, and that works fine, but with Mongrel it doesn't.  I am
wondering if anyone is successfully monitoring Mongrel instances from an

As further info...  I've been working with F5 tech support on this, and
we're both stumped at the moment.  The same HTTP monitor works fine with
Nginx.  Both try to fetch the same HTML file.  Also, if I am ssh'ed in to
the F5, and do a telnet to one of the Mongrels and do "GET /heartbeat.html
HTTP/1.1", followed by two returns, this works fine.  I use that same string
(and two \n's) in my F5's send string for it's HTTP monitor.  According to
F5 who looked at our tcpdump, the Mongrel just never responds (but in the
same dump, they see the direct telnet version respond fine).  The F5 makes a
direct TCP request to do this.

Any ideas?  Suggestions?  Known issue?  Workarounds?  Anyone successful with
this type of setup?

As an FYI, our system info:

CentOS 5, nearly all up to date, 64bit, Core 2 Duo processor
Mongrel 1.0.1
Mongrel Cluster 1.0.2
Ruby 1.8.5 (2006-08-25) [x86_64-linux]

F5 BigIP LTM, currently running 9.1.2 (working on moving to 9.3)
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