Hi,
I'm using a set of promised to guarantee some magic words are poked into
pseudo-files under /sys on linux. The following construct generates an
error message (cosmetic only, but still annoying) when there are no
disks found:-
vars:
"vdisklist" string => execresult("<find_vdisks>", "noshell");
"virt_disk" slist => splitstring( ${vdisklist},"$(const.endl)","99");
"sched_$(virt_disk)" string => execresult("/bin/cat
/sys/block/$(virt_disk)/queue/scheduler", "noshell");
classes:
"noop_$(virt_disk)" expression => regcmp("^.*(\[noop\]|none).*$",
"$(sched_$(virt_disk))");
commands:
"/bin/echo noop > /sys/block/$(virt_disk)/queue/scheduler"
contain => in_shell,
ifvarclass => "!noop_$(virt_disk)";
The "<find_vdisks>" is just a long find command that returns a list of
the devices I'm interested in. The point of this is to guarantee the
scheduler type is set correctly, and my actual config is more complex,
as it defines machine types. However, this test fragment generates the
error message:-
cf3> Q: ".../bin/echo noop ": sh: cannot create
/sys/block//queue/scheduler: Directory nonexistent
cf3> I: Last 1 quoted lines were generated by promiser "/bin/echo noop >
/sys/block//queue/scheduler"
My understanding of this was that if $(vdisklist) was an empty string,
then $(virt_disk) would be an empty list, the regcmp would never match,
and the commands promise would never run, as the ifvarclass would
prevent is from working.
However, what seems to be happening is that a class "noop_" gets defined
even though the regcmp operation can't be matching, and then cfengine
tries to execute a nonsensical commands promise.
I've tried changing "expression" to "or" in the classes promise, but
that broke it in other ways (this config fragment sets a different
scheduler for real physical disks, and that stopped working). Can anyone
explain why I'm seeing this behaviour, and what I can do to prevent it?
Thanks,
Mike
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