On Thu, 5 Feb 2015, Dennis Chen wrote:
> On Thu, Feb 5, 2015 at 4:51 PM, Sage Weil <sage@xxxxxxxxxxxx> wrote:
> > On Thu, 5 Feb 2015, Dennis Chen wrote:
> >> Hello,
> >>
> >> Just as the subject indicated, how can I notify an object watcher
> >> within a class '.so' loaded into osd deamon. I checked the code and
> >> found the below op code defined already:CEPH_OSD_OP_NOTIFY, but this
> >> op code is not used by existing ceph class api, I guest there must be
> >> a simple solution to resolve this if I don't want to make the osd to
> >> play client role the same time.
> >>
> >> Anyone can help me out this?
> >>
> >
> > The watch/notify does not rely on rados classes, e.g.:
> >
> > rados -p rbd create foo
> > rados -p rbd watch foo &
> > rados -p rbd notify foo hello
> >
> > The notify is just a normal librados operation, and most of those can be
> > called from classes, but it normally blocks for some period until the
> > others acknowledge. If it were wired up in objclass.h you could probably
> > initiate the async notify but there would be no way to check whether it
> > ever arrived, so I'm not sure it would be useful.
> >
> > What are you trying to accomplish?
> >
> > sage
>
> What I am trying is to design a signaling control mechanism based on
> ceph, so the notify will not be in heavy load(just some event state
> needed to report to the client async). Below is the investigation for
> this question, initialy the result is good as expected except that the
> argement transfering between the client watcher callback function and
> the osd class function, the code snippet:
>
> Client side--
>
> void notify_test(uint8_t opcode, uint64_t ver, void *arg)
> {
> char *str = (char *)arg;
> printf("get notify:%s\n", str);
You are using the v1 watch/notify API. If you look at master you'll see
there is a new watch2 operation that gets more useful arguments, like the
data payload. (Actually v1 has the data payload too, but I forget where
it appears. You should still probably target v2 though!)
> }
>
> int main(...)
> {
> ...
> strcpy(arg, "notify: from client");
> err = rados_watch(io, objname, 0, &handle, notify_test, arg);
> err = rados_exec(io, objname, "devctl", "devctl_op", in,
> strlen(in), out, 128);
> ...
> }
>
> OSD side (in the ceph class)--
> int test_class_ext(cls_method_context_t hctx, bufferlist *in, bufferlist *out)
> {
> int ret;
>
> CLS_LOG(0, "+test_class_ext");
> in->append("input data");
> out->append("output data");
Note that out content is discarded. Also, you will never get it, since
you aren't blocking (and can't inside a class) and won't wait for a reply.
The "input data" string should get fed to your notify callback on the
client, though!
> ReplicatedPG::OpContext **pctx = (ReplicatedPG::OpContext **)hctx;
> vector<OSDOp> ops(1);
> ops[0].op.op = CEPH_OSD_OP_NOTIFY;
> ops[0].indata = *in;
> ops[0].outdata = *out;
can just leave outdata NULL.
> ret = (*pctx)->pg->do_osd_ops(*pctx, ops);
> in->claim(ops[0].indata);
This isn't needed, and might be eating your notify payload?
> out->claim(ops[0].outdata);
not needed
sage
> CLS_LOG(0, "ret = %d", ret);
>
> return 0;
> }
>
> static int devctl_op(cls_method_context_t hctx, bufferlist *in, bufferlist *out)
> {
> ...
> test_class_ext(hctx, in, out);
> return 0;
> }
>
>
> The output in the client:
> get notify:notify: from client
>
>
> I can't pass the parameters to the client watcher currently :( , any hints?
>
> --
> Den
> --
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>
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