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94 lines
4.0 KiB
Go
94 lines
4.0 KiB
Go
/*
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Copyright 2015 The Kubernetes Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package schedulercache
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import (
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"k8s.io/kubernetes/pkg/api"
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"k8s.io/kubernetes/pkg/labels"
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)
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// Cache collects pods' information and provides node-level aggregated information.
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// It's intended for generic scheduler to do efficient lookup.
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// Cache's operations are pod centric. It does incremental updates based on pod events.
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// Pod events are sent via network. We don't have guaranteed delivery of all events:
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// We use Reflector to list and watch from remote.
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// Reflector might be slow and do a relist, which would lead to missing events.
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//
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// State Machine of a pod's events in scheduler's cache:
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//
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//
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// +-------------------------------------------+ +----+
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// | Add | | |
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// | | | | Update
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// + Assume Add v v |
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//Initial +--------> Assumed +------------+---> Added <--+
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// ^ + + | +
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// | | | | |
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// | | | Add | | Remove
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// | | | | |
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// | | | + |
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// +----------------+ +-----------> Expired +----> Deleted
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// Forget Expire
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//
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//
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// Note that an assumed pod can expire, because if we haven't received Add event notifying us
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// for a while, there might be some problems and we shouldn't keep the pod in cache anymore.
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//
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// Note that "Initial", "Expired", and "Deleted" pods do not actually exist in cache.
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// Based on existing use cases, we are making the following assumptions:
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// - No pod would be assumed twice
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// - A pod could be added without going through scheduler. In this case, we will see Add but not Assume event.
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// - If a pod wasn't added, it wouldn't be removed or updated.
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// - Both "Expired" and "Deleted" are valid end states. In case of some problems, e.g. network issue,
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// a pod might have changed its state (e.g. added and deleted) without delivering notification to the cache.
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type Cache interface {
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// AssumePod assumes a pod scheduled and aggregates the pod's information into its node.
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// The implementation also decides the policy to expire pod before being confirmed (receiving Add event).
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// After expiration, its information would be subtracted.
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AssumePod(pod *api.Pod) error
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// ForgetPod removes an assumed pod from cache.
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ForgetPod(pod *api.Pod) error
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// AddPod either confirms a pod if it's assumed, or adds it back if it's expired.
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// If added back, the pod's information would be added again.
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AddPod(pod *api.Pod) error
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// UpdatePod removes oldPod's information and adds newPod's information.
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UpdatePod(oldPod, newPod *api.Pod) error
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// RemovePod removes a pod. The pod's information would be subtracted from assigned node.
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RemovePod(pod *api.Pod) error
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// AddNode adds overall information about node.
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AddNode(node *api.Node) error
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// UpdateNode updates overall information about node.
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UpdateNode(oldNode, newNode *api.Node) error
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// RemoveNode removes overall information about node.
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RemoveNode(node *api.Node) error
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// UpdateNodeNameToInfoMap updates the passed infoMap to the current contents of Cache.
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// The node info contains aggregated information of pods scheduled (including assumed to be)
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// on this node.
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UpdateNodeNameToInfoMap(infoMap map[string]*NodeInfo) error
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// List lists all cached pods (including assumed ones).
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List(labels.Selector) ([]*api.Pod, error)
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}
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