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101 lines
2.6 KiB
Go
101 lines
2.6 KiB
Go
/*
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Copyright 2017 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 configuration
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import (
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"fmt"
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"sync"
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"time"
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"k8s.io/apimachinery/pkg/runtime"
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"k8s.io/apimachinery/pkg/util/wait"
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)
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const (
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defaultInterval = 1 * time.Second
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defaultFailureThreshold = 5
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)
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type getFunc func() (runtime.Object, error)
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// When running, poller calls `get` every `interval`. If `get` is
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// successful, `Ready()` returns ready and `configuration()` returns the
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// `mergedConfiguration`; if `get` has failed more than `failureThreshold ` times,
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// `Ready()` returns not ready and `configuration()` returns nil configuration.
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// In an HA setup, the poller is consistent only if the `get` is
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// doing consistent read.
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type poller struct {
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// a function to consistently read the latest configuration
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get getFunc
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// consistent read interval
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interval time.Duration
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// if the number of consecutive read failure equals or exceeds the failureThreshold , the
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// configuration is regarded as not ready.
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failureThreshold int
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// if the configuration is regarded as ready.
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ready bool
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mergedConfiguration runtime.Object
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// lock much be hold when reading ready or mergedConfiguration
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lock sync.RWMutex
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}
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func newPoller(get getFunc) *poller {
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return &poller{
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get: get,
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interval: defaultInterval,
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failureThreshold: defaultFailureThreshold,
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}
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}
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func (a *poller) notReady() {
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a.lock.Lock()
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defer a.lock.Unlock()
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a.ready = false
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}
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func (a *poller) configuration() (runtime.Object, error) {
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a.lock.RLock()
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defer a.lock.RUnlock()
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if !a.ready {
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return nil, fmt.Errorf("configuration is not ready")
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}
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return a.mergedConfiguration, nil
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}
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func (a *poller) setConfigurationAndReady(value runtime.Object) {
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a.lock.Lock()
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defer a.lock.Unlock()
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a.mergedConfiguration = value
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a.ready = true
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}
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func (a *poller) Run(stopCh <-chan struct{}) {
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var failure int
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go wait.Until(func() {
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configuration, err := a.get()
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if err != nil {
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failure++
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if failure >= a.failureThreshold {
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a.notReady()
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}
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return
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}
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failure = 0
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a.setConfigurationAndReady(configuration)
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}, a.interval, stopCh)
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}
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