8 Feb
2021
8 Feb
'21
6:17 p.m.
Hi Jiffin,
From my perspective, one simple way to fix this (although we must be
careful with backward compatibility) would be for rgw to register to
service map differently.
Today it is using the daemon name like rgw.foo, then it will register
as foo. Essentially, if you try to run that pod twice you would still
see a single instance in the service map as well as the prometheus
metrics.
It would be nice to register with RADOS client session ID instead ,
just like rbd-mirror does by using instance_id. Something like:
std::string instance_id = stringify(rados->get_instance_id());
int ret = rados.service_daemon_register(daemon_type, name, metadata);
Here https://github.com/ceph/ceph/blob/master/src/rgw/rgw_rados.cc#L1139
With that we can re-use the same cephx user and scale to any number,
all instances will use the same cephx to authenticate to the cluster
but they will show up as N in the service map.
I guess one downside is that as soon as the daemon restart, we get a
new RADOS client session ID, and thus our name changes, which means we
are losing all the metrics...
Thoughts?
Thanks!
–––––––––
Sébastien Han
Senior Principal Software Engineer, Storage Architect
"Always give 100%. Unless you're giving blood."
On Thu, Feb 4, 2021 at 3:39 PM Jiffin Thottan <jthottan(a)redhat.com> wrote:
Hi all,
In OCS(Rook) env workflow for RGW daemons as follows,
Normally for creating ceph object-store, the first Rook creates pools for rgw daemon with
the specified configuration.
Then depending on the no of instances, Rook create cephxuser and then rgw spawn daemon in
the container(pod) using its id
with following arguments for radosgw binary
Args:
--fsid=91501490-4b55-47db-b226-f9d9968774c1
--keyring=/etc/ceph/keyring-store/keyring
--log-to-stderr=true
--err-to-stderr=true
--mon-cluster-log-to-stderr=true
--log-stderr-prefix=debug
--default-log-to-file=false
--default-mon-cluster-log-to-file=false
--mon-host=$(ROOK_CEPH_MON_HOST)
--mon-initial-members=$(ROOK_CEPH_MON_INITIAL_MEMBERS)
--id=rgw.my.store.a
--setuser=ceph
--setgroup=ceph
--foreground
--rgw-frontends=beast port=8080
--host=$(POD_NAME)
--rgw-mime-types-file=/etc/ceph/rgw/mime.types
--rgw-realm=my-store
--rgw-zonegroup=my-store
--rgw-zone=my-store
And here cephxuser will be "client.rgw.my.store.a" and all the pools for rgw
will be created as my-store*. Normally if there is
a request for another instance in the config file for a ceph-object-store config file[1]
for rook, another user "client.rgw.mystore.b"
will be created by rook and will consume the same pools.
There is a feature in Kubernetes known as autoscale in which pods can be automatically
scaled based on specified metrics. If we apply that
feature for rgw pods, Kubernetes will automatically scale the rgw pods(like a clone of
the existing pod) with the same argument for "--id"
based on the metrics, but ceph cannot distinguish those as different rgw daemons even
though multiple pods of rgw are running simultaneously.
In "ceph status" shows only one daemon rgw as well
In vstart or ceph ansible(Ali help me to figure it out), I can see for each rgw daemon a
cephxuser is getting created as well
Is this behaviour intended ? or am I hitting any corner case which was never tested
before?
There is no point of autoscaling of rgw pod if it considered to the same daemon, the s3
client will talk to only one of the pods and ceph mgr
provides metrics can give incorrect data as well which can affect the autoscale feature
Also opened an issue in rook for the time being [2]
[1]
https://github.com/rook/rook/blob/master/cluster/examples/kubernetes/ceph/o…
[2] https://github.com/rook/rook/issues/6943
Regards,
Jiffin