ceph-csi/internal/util/pidlimit.go

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provisioners: add reconfiguring of PID limit 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>
2019-07-26 12:36:43 +00:00
/*
Copyright 2019 The Ceph-CSI Authors.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
package util
import (
"bufio"
"fmt"
"io"
"os"
"strconv"
"strings"
)
const (
procCgroup = "/proc/self/cgroup"
sysPidsMaxFmt = "/sys/fs/cgroup/pids%s/pids.max"
)
// return the cgouprs "pids.max" file of the current process
//
// find the line containing the pids group from the /proc/self/cgroup file
// $ grep 'pids' /proc/self/cgroup
// 7:pids:/kubepods.slice/kubepods-besteffort.slice/....scope
// $ cat /sys/fs/cgroup/pids + *.scope + /pids.max
func getCgroupPidsFile() (string, error) {
cgroup, err := os.Open(procCgroup)
if err != nil {
return "", err
}
defer cgroup.Close()
scanner := bufio.NewScanner(cgroup)
var slice string
for scanner.Scan() {
parts := strings.Split(scanner.Text(), ":")
if parts == nil || len(parts) < 3 {
continue
}
if parts[1] == "pids" {
slice = parts[2]
break
}
}
if slice == "" {
return "", fmt.Errorf("could not find a cgroup for 'pids'")
}
pidsMax := fmt.Sprintf(sysPidsMaxFmt, slice)
return pidsMax, nil
}
// GetPIDLimit returns the current PID limit, or an error. A value of -1
// translates to "max".
func GetPIDLimit() (int, error) {
pidsMax, err := getCgroupPidsFile()
if err != nil {
return 0, err
}
2019-08-30 10:23:10 +00:00
f, err := os.Open(pidsMax) // #nosec - intended reading from /sys/...
provisioners: add reconfiguring of PID limit 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>
2019-07-26 12:36:43 +00:00
if err != nil {
return 0, err
}
defer f.Close()
maxPidsStr, err := bufio.NewReader(f).ReadString('\n')
if err != nil && err != io.EOF {
return 0, err
}
maxPidsStr = strings.TrimRight(maxPidsStr, "\n")
maxPids := -1
if maxPidsStr != "max" {
maxPids, err = strconv.Atoi(maxPidsStr)
if err != nil {
return 0, err
}
}
return maxPids, nil
}
// SetPIDLimit configures the given PID limit for the current process. A value
// of -1 translates to "max".
func SetPIDLimit(limit int) error {
limitStr := "max"
if limit != -1 {
limitStr = fmt.Sprintf("%d", limit)
}
pidsMax, err := getCgroupPidsFile()
if err != nil {
return err
}
f, err := os.Create(pidsMax)
if err != nil {
return err
}
defer f.Close()
_, err = f.WriteString(limitStr)
if err != nil {
return err
}
return nil
}