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Scheduler predicate for capping node volume count

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For certain volume types (e.g. AWS EBS or GCE PD), a limitted
number of such volumes can be attached to a given node.  This commit
introduces a predicate with allows cluster admins to cap
the maximum number of volumes matching a particular type attached to a
given node.

The volume type is configurable by passing a pair of filter functions,
and the maximum number of such volumes is configurable to allow node
admins to reserve a certain number of volumes for system use.

By default, the predicate is exposed as MaxEBSVolumeCount and
MaxGCEPDVolumeCount (for AWS ElasticBlocKStore and GCE PersistentDisk
volumes, respectively), each of which can be configured using the
`KUBE_MAX_PD_VOLS` environment variable.

Fixes #7835
This commit is contained in:
Solly Ross
2016-01-14 15:45:08 -05:00
parent 7489cb6e79
commit 2d436ff080
4 changed files with 427 additions and 0 deletions
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47
plugin/pkg/scheduler/algorithmprovider/defaults/defaults.go
View File

@@ -18,14 +18,41 @@ limitations under the License.
package defaults
import (
"os"
"strconv"
"k8s.io/kubernetes/pkg/util/sets"
"k8s.io/kubernetes/plugin/pkg/scheduler"
"k8s.io/kubernetes/plugin/pkg/scheduler/algorithm"
"k8s.io/kubernetes/plugin/pkg/scheduler/algorithm/predicates"
"k8s.io/kubernetes/plugin/pkg/scheduler/algorithm/priorities"
"k8s.io/kubernetes/plugin/pkg/scheduler/factory"
"github.com/golang/glog"
)
// Amazon reccomends having no more that 40 volumes attached to an instance,
// and at least one of those is for the system root volume.
const DefaultMaxEBSVolumes = 39
// GCE instances can have up to 16 PD volumes attached.
const DefaultMaxGCEPDVolumes = 16
// getMaxVols checks the max PD volumes environment variable, otherwise returning a default value
func getMaxVols(defaultVal int) int {
if rawMaxVols := os.Getenv("KUBE_MAX_PD_VOLS"); rawMaxVols != "" {
if parsedMaxVols, err := strconv.Atoi(rawMaxVols); err != nil {
glog.Errorf("Unable to parse maxiumum PD volumes value, using default of %v: %v", defaultVal, err)
} else if parsedMaxVols <= 0 {
glog.Errorf("Maximum PD volumes must be a positive value, using default of %v", defaultVal)
} else {
return parsedMaxVols
}
}
return defaultVal
}
func init() {
factory.RegisterAlgorithmProvider(factory.DefaultProvider, defaultPredicates(), defaultPriorities())
// EqualPriority is a prioritizer function that gives an equal weight of one to all nodes
@@ -80,6 +107,26 @@ func defaultPredicates() sets.String {
),
// Fit is determined by the presence of the Host parameter and a string match
factory.RegisterFitPredicate("HostName", predicates.PodFitsHost),
// Fit is determined by whether or not there would be too many AWS EBS volumes attached to the node
factory.RegisterFitPredicateFactory(
"MaxEBSVolumeCount",
func(args factory.PluginFactoryArgs) algorithm.FitPredicate {
// TODO: allow for generically parameterized scheduler predicates, because this is a bit ugly
maxVols := getMaxVols(DefaultMaxEBSVolumes)
return predicates.NewMaxPDVolumeCountPredicate(predicates.EBSVolumeFilter, maxVols, args.PVInfo, args.PVCInfo)
},
),
// Fit is determined by whether or not there would be too many GCE PD volumes attached to the node
factory.RegisterFitPredicateFactory(
"MaxGCEPDVolumeCount",
func(args factory.PluginFactoryArgs) algorithm.FitPredicate {
// TODO: allow for generically parameterized scheduler predicates, because this is a bit ugly
maxVols := getMaxVols(DefaultMaxGCEPDVolumes)
return predicates.NewMaxPDVolumeCountPredicate(predicates.GCEPDVolumeFilter, maxVols, args.PVInfo, args.PVCInfo)
},
),
)
}