[Linux-HA] ocf:heartbeat:apache resource agent and timeouts
dejanmm at fastmail.fm
Fri Apr 6 05:15:37 MDT 2012
On Thu, Apr 05, 2012 at 11:54:44AM -0500, Dimitri Maziuk wrote:
> On 4/5/2012 10:09 AM, Dejan Muhamedagic wrote:
> > On Wed, Apr 04, 2012 at 11:21:15AM -0500, Dimitri Maziuk wrote:
> >> On 04/04/2012 10:59 AM, Dejan Muhamedagic wrote:
> >>> Hi,
> >> ... httpd monitor ...
> >>> It may be wrong or not, that depends on what you need.
> >> (Another questionable choice as I recall was to consider 4xx an error.
> >> Dep. on what you need, you may want to treat only some 5xx codes as
> >> errors b/c the others mean apache is up and answering properly.)
> > Isn't the status page always supposed to return, well, the
> > status?
> No. From http://httpd.apache.org/docs/2.2/mod/mod_status.html:
> "The Status module allows a server administrator to find out how well
> their server is performing. A HTML page is presented that gives the
> current server statistics in an easily readable form."
Oh, darn, I did mean that when I said "status." And the point was
that it should _always_ yield some valid html.
> What cluster should monitor for is that httpd is running and answering
> requests. For that purpose a "404 Not found" is a success (while "500
> Internal server failure" probably isn't).
OK, so getting /server-status doesn't mean that httpd is running
and answering requests?
> "How well the server is performing" implies that it's up and running, so
> it's a valid test -- in the same sense that counting ice cubes in the
> freezer compartment is a valid test to see if your fridge is working.
Oh, well... and isn't it?
> >> Which is precisely what I do: I monitor on the host with (more or less)
> >> "lsof -i | grep httpd.+\*:http"
> > How is that better than fetching the status page?
> It's not. It tells me httpd is running and is bound to ip/port. It does
> not tell me if the port is reachable on a particular ip (but neither
> does the resource agent) or whether it serves what it's supposed to
> serve (but again neither does the agent since in my config
> /server-status is *supposed* to return 404).
> The point is that if you tested your apache & iptables setup and http's
> up and bound to the port, the reasons it wouldn't answer requests are
> pretty much limited to DOS on the server or on the connection. And since
> the resource agent isn't really monitoring those either, the only
> practical difference is that my check has fewer breakable pieces.
And that you have yet another piece of software to install and
take care of :) But I'm sure you know the best.
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