Upgrading Ceph in Docker Swarm

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This post is a followup to an earlier blog bost regarding setting up a docker-swarm cluster with ceph.

I’ve been running this cluster for a while now quite happily however since setting it up, a new version of ceph has been released - nautilus - so now it’s time for some upgrades.

I’ve mostly followed https://docs.ceph.com/docs/master/releases/nautilus/#upgrading-from-mimic-or-luminous but adapted it for the fact we’re running everything in docker. I recommend that you have a read though this yourself first to have an idea of what we are doing and why.

(It’s worth noting at this point that this guide was mostly written after the fact based on command history so I may have missed something. It’s always a good idea to do this on a test cluster first, or in a maintenance window!)

Before we begin the upgrade, we should run the following on each node in advance to save time later: docker pull ceph/daemon:latest-nautilus

Now we can prepare to update. Firstly on any node we tell ceph not to worry about rebalancing:

ceph osd set noout

Now we can begin actually upgrading ceph. The process is actually quite simple for each daemon type, on each node we stop and remove the old container, then start a new one with the same flags we did in the past, so here we go:

On each node 1 at a time restart the ceph-mon containers:

docker stop ceph-mon; docker rm ceph-mon
docker run -d --net=host --restart always -v /etc/ceph:/etc/ceph -v /var/lib/ceph/:/var/lib/ceph/ \
-e MON_IP=$(ip addr show dev eth0 | grep "inet " | head -n 1 | awk '{print $2}' | awk -F/ '{print $1}') \
-e CEPH_PUBLIC_NETWORK=$(ip route show dev eth0 | grep link | grep -v 169.254.0.0 | awk '{print $1}') \
--name="ceph-mon" ceph/daemon:latest-nautilus mon

(This is basically the same command that was used before, except we’re now specifying that we want to use ceph/daemon:latest-nautilus as the image source)

After we have done this, we can check that the upgrade was successful:

ceph mon versions should show something like:

{
    "ceph version 14.2.2 (4f8fa0a0024755aae7d95567c63f11d6862d55be) nautilus (stable)": 3
}

Now the same for the mgr containers:

docker stop ceph-mgr; docker rm ceph-mgr
docker run -d --net=host --privileged=true --pid=host -v /etc/ceph:/etc/ceph -v /var/lib/ceph/:/var/lib/ceph/ --name="ceph-mgr" --restart=always ceph/daemon:latest-nautilus mgr

Checking with ceph mgr versions

And the osd containers:

docker stop ceph-osd; docker rm ceph-osd
docker run -d --net=host --privileged=true --pid=host -v /etc/ceph:/etc/ceph -v /var/lib/ceph/:/var/lib/ceph/ -v /dev/:/dev/ -e OSD_DEVICE=/dev/sdb -e OSD_TYPE=disk --name="ceph-osd" --restart=always ceph/daemon:latest-nautilus osd

Checking with ceph osd versions (You might want to wait for the output of this command to show that the current node is running the new version before moving on to the next node)

Now we can move onto the MDS containers.

Firstly we need to change max_mds to 1 if it’s not already (You can check using ceph fs get cephfs):

ceph fs set cephfs max_mds 1

Now we should stop all the non-active MDSs. We can see the currently active MDS using: ceph status | grep -i mds

And we stop the non-active standby MDSs using:

docker stop ceph-mds; docker rm ceph-mds

And then once ceph status shows only the active MDS, we can restart the remaining one:

docker stop ceph-mds; docker rm ceph-mds
docker run -d --net=host --name ceph-mds --restart always -v /var/lib/ceph/:/var/lib/ceph/ -v /etc/ceph:/etc/ceph -e CEPHFS_CREATE=1 -e CEPHFS_DATA_POOL_PG=128 -e CEPHFS_METADATA_POOL_PG=128 ceph/daemon:latest-nautilus mds

And then restart all the standby MDSs:

docker run -d --net=host --name ceph-mds --restart always -v /var/lib/ceph/:/var/lib/ceph/ -v /etc/ceph:/etc/ceph -e CEPHFS_CREATE=1 -e CEPHFS_DATA_POOL_PG=128 -e CEPHFS_METADATA_POOL_PG=128 ceph/daemon:latest-nautilus mds

At this point, the max_mds value can be reset if it was previously anything other than 1.

And now we can check ceph mds versions shows our updated MDSs:

{
    "ceph version 14.2.2 (4f8fa0a0024755aae7d95567c63f11d6862d55be) nautilus (stable)": 3
}

Now for some post-upgrade house keeping, on any node:

ceph osd require-osd-release nautilus
ceph osd unset noout
ceph mon enable-msgr2

We should also now update our config files and local version of ceph.

Firstly lets import our current config files into the cluster configuration db, run this on all nodes:

ceph config assimilate-conf -i /etc/ceph/ceph.conf

Then we can upgrade the local ceph tools:

rpm -e ceph-release; rpm -Uvh https://download.ceph.com/rpm-nautilus/el7/noarch/ceph-release-1-1.el7.noarch.rpm
yum clean all; yum update ceph

And update our local config to the minimal config:

cp -f /etc/ceph/ceph.conf /etc/ceph/ceph.conf.old
ceph config generate-minimal-conf > /etc/ceph/ceph.conf.new
mv -f /etc/ceph/ceph.conf.new /etc/ceph/ceph.conf

We should also update our fstab entry to include multiple servers not just the current one, so that we can actually mount properly on startup (this should have been done in the original guide. I learned afterwards!):

export CEPHMON=`ceph mon dump 2>&1 | grep "] mon." | awk '{print $3}' | sed -r 's/mon.(.*)/\1:6789/g'`
sed -ri "s/.*(:\/\s+\/var\/data\/.*)/$(echo ${CEPHMON} | sed 's/ /,/g')\1/" /etc/fstab

This may also now be a good time for other OS updates and a reboot if required (Run ceph osd set noout first to stop ceph rebalancing when the node goes down and check ceph status to see if the current node is the active MDS and fail it if it is with ceph mds fail $(hostname -s) and then ceph osd unset noout when we’re done.)

Before rebooting we will want to drain the node of active containers:

docker node update --availability drain `hostname -f`

and then undrain it when we’re done:

docker node update --availability active `hostname -f`

And that’s it! Overall a pretty painless upgrade process, which is nice.