kubernetes: k8s.io/kubernetes/pkg/scheduler/internal/cache Index | Files | Directories

package cache

import "k8s.io/kubernetes/pkg/scheduler/internal/cache"


Package Files

cache.go interface.go node_tree.go

type Cache Uses

type Cache interface {

    // AssumePod assumes a pod scheduled and aggregates the pod's information into its node.
    // The implementation also decides the policy to expire pod before being confirmed (receiving Add event).
    // After expiration, its information would be subtracted.
    AssumePod(pod *v1.Pod) error

    // FinishBinding signals that cache for assumed pod can be expired
    FinishBinding(pod *v1.Pod) error

    // ForgetPod removes an assumed pod from cache.
    ForgetPod(pod *v1.Pod) error

    // AddPod either confirms a pod if it's assumed, or adds it back if it's expired.
    // If added back, the pod's information would be added again.
    AddPod(pod *v1.Pod) error

    // UpdatePod removes oldPod's information and adds newPod's information.
    UpdatePod(oldPod, newPod *v1.Pod) error

    // RemovePod removes a pod. The pod's information would be subtracted from assigned node.
    RemovePod(pod *v1.Pod) error

    // GetPod returns the pod from the cache with the same namespace and the
    // same name of the specified pod.
    GetPod(pod *v1.Pod) (*v1.Pod, error)

    // IsAssumedPod returns true if the pod is assumed and not expired.
    IsAssumedPod(pod *v1.Pod) (bool, error)

    // AddNode adds overall information about node.
    AddNode(node *v1.Node) error

    // UpdateNode updates overall information about node.
    UpdateNode(oldNode, newNode *v1.Node) error

    // RemoveNode removes overall information about node.
    RemoveNode(node *v1.Node) error

    // UpdateNodeInfoSnapshot updates the passed infoSnapshot to the current contents of Cache.
    // The node info contains aggregated information of pods scheduled (including assumed to be)
    // on this node.
    UpdateNodeInfoSnapshot(nodeSnapshot *nodeinfosnapshot.Snapshot) error

    // Snapshot takes a snapshot on current cache
    Snapshot() *Snapshot

Cache collects pods' information and provides node-level aggregated information. It's intended for generic scheduler to do efficient lookup. Cache's operations are pod centric. It does incremental updates based on pod events. Pod events are sent via network. We don't have guaranteed delivery of all events: We use Reflector to list and watch from remote. Reflector might be slow and do a relist, which would lead to missing events.

State Machine of a pod's events in scheduler's cache:

+-------------------------------------------+  +----+
|                            Add            |  |    |
|                                           |  |    | Update
+      Assume                Add            v  v    |

Initial +--------> Assumed +------------+---> Added <--+

^                +   +               |       +
|                |   |               |       |
|                |   |           Add |       | Remove
|                |   |               |       |
|                |   |               +       |
+----------------+   +-----------> Expired   +----> Deleted
      Forget             Expire

Note that an assumed pod can expire, because if we haven't received Add event notifying us for a while, there might be some problems and we shouldn't keep the pod in cache anymore.

Note that "Initial", "Expired", and "Deleted" pods do not actually exist in cache. Based on existing use cases, we are making the following assumptions: - No pod would be assumed twice - A pod could be added without going through scheduler. In this case, we will see Add but not Assume event. - If a pod wasn't added, it wouldn't be removed or updated. - Both "Expired" and "Deleted" are valid end states. In case of some problems, e.g. network issue,

a pod might have changed its state (e.g. added and deleted) without delivering notification to the cache.

func New Uses

func New(ttl time.Duration, stop <-chan struct{}) Cache

New returns a Cache implementation. It automatically starts a go routine that manages expiration of assumed pods. "ttl" is how long the assumed pod will get expired. "stop" is the channel that would close the background goroutine.

type Snapshot Uses

type Snapshot struct {
    AssumedPods map[string]bool
    Nodes       map[string]*schedulernodeinfo.NodeInfo

Snapshot is a snapshot of cache state



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