772ab8e1b4
Handle failure cases on startup gracefully to avoid causing cascading errors and poor initialization in other components. Initial errors from config load cause the initializer to pause and hold requests. Return typed errors to better communicate failures to clients. Add code to handle two specific cases - admin wants to bypass initialization defaulting, and mirror pods (which want to bypass initialization because the kubelet owns their lifecycle).
121 lines
2.9 KiB
Go
121 lines
2.9 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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var (
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ErrNotReady = fmt.Errorf("configuration is not ready")
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ErrDisabled = fmt.Errorf("disabled")
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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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// number of consecutive failures so far.
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failures 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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lastErr error
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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) lastError(err error) {
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a.lock.Lock()
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defer a.lock.Unlock()
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a.lastErr = err
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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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if a.lastErr != nil {
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return nil, a.lastErr
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}
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return nil, ErrNotReady
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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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a.lastErr = nil
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}
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func (a *poller) Run(stopCh <-chan struct{}) {
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go wait.Until(a.sync, a.interval, stopCh)
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}
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func (a *poller) sync() {
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configuration, err := a.get()
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if err != nil {
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a.failures++
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a.lastError(err)
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if a.failures >= 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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a.failures = 0
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a.setConfigurationAndReady(configuration)
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}
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