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provisioners: add reconfiguring of PID limit

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The container runtime CRI-O limits the number of PIDs to 1024 by
default. When many PVCs are requested at the same time, it is possible
for the provisioner to start too many threads (or go routines) and
executing 'rbd' commands can start to fail. In case a go routine can not
get started, the process panics.

The PID limit can be changed by passing an argument to kubelet, but this
will affect all pids running on a host. Changing the parameters to
kubelet is also not a very elegant solution.

Instead, the provisioner pod can change the configuration itself. The
pod is running in privileged mode and can write to /sys/fs/cgroup where
the limit is configured.

With this change, the limit is configured to 'max', just as if there is
no limit at all. The logs of the csi-rbdplugin in the provisioner pod
will reflect the change it makes when starting the service:

    $ oc -n rook-ceph logs -c csi-rbdplugin csi-rbdplugin-provisioner-0
    ..
    I0726 13:59:19.737678       1 cephcsi.go:127] Initial PID limit is set to 1024
    I0726 13:59:19.737746       1 cephcsi.go:136] Reconfigured PID limit to -1 (max)
    ..

It is possible to pass a different limit on the commandline of the
cephcsi executable. The following flag has been added:

    --pidlimit=<int>       the PID limit to configure through cgroups

This accepts special values -1 (max) and 0 (default, do not
reconfigure). Other integers will be the limit that gets configured in
cgroups.

Signed-off-by: Niels de Vos <ndevos@redhat.com>
This commit is contained in:
Niels de Vos
2019-07-26 14:36:43 +02:00
committed by mergify[bot]
parent 885ec7049d
commit 31648c8feb
13 changed files with 198 additions and 0 deletions
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docs/deploy-cephfs.md
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@ -53,6 +53,7 @@ that should be resolved in v14.2.3.
| `--instanceid` | "default" | Unique ID distinguishing this instance of Ceph CSI among other instances, when sharing Ceph clusters across CSI instances for provisioning |
| `--pluginpath` | "/var/lib/kubelet/plugins/" | The location of cephcsi plugin on host |
| `--metadatastorage` | _empty_ | Points to where older (1.0.0 or older plugin versions) metadata about provisioned volumes are kept, as file or in as k8s configmap (`node` or `k8s_configmap` respectively) |
| `--pidlimit` | _0_ | Configure the PID limit in cgroups. The container runtime can restrict the number of processes/tasks which can cause problems while provisioning (or deleting) a large number of volumes. A value of `-1` configures the limit to the maximum, `0` does not configure limits at all. |
**Available environmental variables:**

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docs/deploy-rbd.md
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@ -35,6 +35,7 @@ make image-cephcsi
| `--containerized` | true | Whether running in containerized mode |
| `--instanceid` | "default" | Unique ID distinguishing this instance of Ceph CSI among other instances, when sharing Ceph clusters across CSI instances for provisioning |
| `--metadatastorage` | _empty_ | Points to where legacy (1.0.0 or older plugin versions) metadata about provisioned volumes are kept, as file or in as k8s configmap (`node` or `k8s_configmap` respectively) |
| `--pidlimit` | _0_ | Configure the PID limit in cgroups. The container runtime can restrict the number of processes/tasks which can cause problems while provisioning (or deleting) a large number of volumes. A value of `-1` configures the limit to the maximum, `0` does not configure limits at all. |
**Available volume parameters:**