Developing with cephadm¶
There are several ways to develop with cephadm. Which you use depends on what you’re trying to accomplish.
Start a cluster with vstart, with cephadm configured
Manage any additional daemons with cephadm
In this case, the mon and manager at a minimum are running in the usual vstart way, not managed by cephadm. But cephadm is enabled and the local host is added, so you can deploy additional daemons or add additional hosts.
This works well for developing cephadm itself, because any mgr/cephadm
or cephadm/cephadm code changes can be applied by kicking ceph-mgr
ceph mgr fail x. (When the mgr (re)starts, it loads the
cephadm/cephadm script into memory.)
MON=1 MGR=1 OSD=0 MDS=0 ../src/vstart.sh -d -n -x --cephadm
~/.ssh/id_dsa[.pub]is used as the cluster key. It is assumed that this key is authorized to ssh with no passphrase to root@`hostname`.
cephadm does not try to manage any daemons started by vstart.sh (any nonzero number in the environment variables). No service spec is defined for mon or mgr.
You’ll see health warnings from cephadm about stray daemons–that’s because the vstart-launched daemons aren’t controlled by cephadm.
The default image is
quay.io/ceph-ci/ceph:master, but you can change this by passing
ceph config set global container_image ....
cstart and cpatch¶
cstart.sh script will launch a cluster using cephadm and put the
conf and keyring in your build dir, so that the
bin/ceph ... CLI works
(just like with vstart). The
ckill.sh script will tear it down.
A unique but stable fsid is stored in
fsid(in the build dir).
The mon port is random, just like with vstart.
The container image is
quay.io/ceph-ci/ceph:$tagwhere $tag is the first 8 chars of the fsid.
If the container image doesn’t exist yet when you run cstart for the first time, it is built with cpatch.
There are a few advantages here:
The cluster is a “normal” cephadm cluster that looks and behaves just like a user’s cluster would. In contract, vstart and teuthology clusters tend to be special in subtle (and not-so-subtle) ways.
To start a test cluster:
The last line of this will be a line you can cut+paste to update the container image. For instance:
sudo ../src/script/cpatch -t quay.io/ceph-ci/ceph:8f509f4e
By default, cpatch will patch everything it can think of from the local build dir into the container image. If you are working on a specific part of the system, though, can you get away with smaller changes so that cpatch runs faster. For instance:
sudo ../src/script/cpatch -t quay.io/ceph-ci/ceph:8f509f4e --py
will update the mgr modules (minus the dashboard). Or:
sudo ../src/script/cpatch -t quay.io/ceph-ci/ceph:8f509f4e --core
will do most binaries and libraries. Pass
-h to cpatch for all options.
Once the container is updated, you can refresh/restart daemons by bouncing them with:
sudo systemctl restart ceph-`cat fsid`.target
When you’re done, you can tear down the cluster with:
sudo ../src/ckill.sh # or, sudo ../src/cephadm/cephadm rm-cluster --force --fsid `cat fsid`
Note regarding network calls from CLI handlers¶
Executing any cephadm CLI commands like
ceph orch ls will block the
mon command handler thread within the MGR, thus preventing any concurrent
CLI calls. Note that pressing
^C will not resolve this situation,
as only the client will be aborted, but not execution of the command
within the orchestrator manager module itself. This means, cephadm will
be completely unresponsive until the execution of the CLI handler is
fully completed. Note that even
ceph orch ps will not respond while
another handler is executing.
This means we should do very few synchronous calls to remote hosts.
As a guideline, cephadm should do at most
O(1) network calls in CLI handlers.
Everything else should be done asynchronously in other threads, like