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Move to a structured status for dynamic kubelet config #63314

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May 16, 2018
Merged

Move to a structured status for dynamic kubelet config #63314

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25 changes: 25 additions & 0 deletions api/openapi-spec/swagger.json
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26 changes: 26 additions & 0 deletions api/swagger-spec/v1.json
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43 changes: 30 additions & 13 deletions cmd/kubelet/app/server.go
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Original file line number Diff line number Diff line change
Expand Up @@ -198,25 +198,43 @@ HTTP server: The kubelet can also listen for HTTP and respond to a simple API
}
}

// TODO(#63305): always validate the combination of the local config file and flags, this is the fallback
// when the dynamic config controller tells us to use local config (this can be fixed alongside other validation fixes).

// use dynamic kubelet config, if enabled
var kubeletConfigController *dynamickubeletconfig.Controller
if dynamicConfigDir := kubeletFlags.DynamicConfigDir.Value(); len(dynamicConfigDir) > 0 {
kubeletConfig, kubeletConfigController, err = BootstrapKubeletConfigController(kubeletConfig, dynamicConfigDir)
var dynamicKubeletConfig *kubeletconfiginternal.KubeletConfiguration
dynamicKubeletConfig, kubeletConfigController, err = BootstrapKubeletConfigController(dynamicConfigDir)
if err != nil {
glog.Fatal(err)
}
// We must enforce flag precedence by re-parsing the command line into the new object.
// This is necessary to preserve backwards-compatibility across binary upgrades.
// See issue #56171 for more details.
if err := kubeletConfigFlagPrecedence(kubeletConfig, args); err != nil {
glog.Fatal(err)
}
// update feature gates based on new config
if err := utilfeature.DefaultFeatureGate.SetFromMap(kubeletConfig.FeatureGates); err != nil {
glog.Fatal(err)
// If we should just use our existing, local config, the controller will return a nil config
if dynamicKubeletConfig != nil {
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nit: i'm generally not a fan of giving nil an implicit meaning. I would rather have an explicit return value indicating if we should use local or remote.

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@mtaufen mtaufen May 11, 2018 •
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I'm not sure I agree in this case.
The controller bootstrap returns the dynamic config if it exists.
If there's no dynamic config to use it returns nil (nil => Nothing is a common idiom in Go).
In the case that there's no dynamic config to use, we just move on and use the local.

I think adding a fourth return value to tag the result is unnecessary, given the ubiquity of that idiom.

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sgtm

kubeletConfig = dynamicKubeletConfig
// We must enforce flag precedence by re-parsing the command line into the new object.
// This is necessary to preserve backwards-compatibility across binary upgrades.
// See issue #56171 for more details.
if err := kubeletConfigFlagPrecedence(kubeletConfig, args); err != nil {
glog.Fatal(err)
}
// update feature gates based on new config
if err := utilfeature.DefaultFeatureGate.SetFromMap(kubeletConfig.FeatureGates); err != nil {
glog.Fatal(err)
}
}
}

// TODO(#63305): need to reconcile that validation performed inside the dynamic config controller
// will happen against currently set feature gates, rather than future adjustments from combination of files
// and flags. There's a potential scenario where a valid config (because it sets new gates) is considered
// invalid against current gates (at least until --feature-gates flag is removed).
// We should validate against the combination of current feature gates, overrides from feature gates in the file,
// and overrides from feature gates set via flags, rather than currently set feature gates.
// Once the --feature-gates flag is removed, we should strictly validate against the combination of current
// feature gates and feature gates in the file (always need to validate against the combo, because feature-gates
// can layer between the file and dynamic config right now - though maybe we should change this).

// construct a KubeletServer from kubeletFlags and kubeletConfig
kubeletServer := &options.KubeletServer{
KubeletFlags: *kubeletFlags,
Expand Down Expand Up @@ -1089,8 +1107,7 @@ func parseResourceList(m map[string]string) (v1.ResourceList, error) {
}

// BootstrapKubeletConfigController constructs and bootstrap a configuration controller
func BootstrapKubeletConfigController(defaultConfig *kubeletconfiginternal.KubeletConfiguration,
dynamicConfigDir string) (*kubeletconfiginternal.KubeletConfiguration, *dynamickubeletconfig.Controller, error) {
func BootstrapKubeletConfigController(dynamicConfigDir string) (*kubeletconfiginternal.KubeletConfiguration, *dynamickubeletconfig.Controller, error) {
if !utilfeature.DefaultFeatureGate.Enabled(features.DynamicKubeletConfig) {
return nil, nil, fmt.Errorf("failed to bootstrap Kubelet config controller, you must enable the DynamicKubeletConfig feature gate")
}
Expand All @@ -1104,7 +1121,7 @@ func BootstrapKubeletConfigController(defaultConfig *kubeletconfiginternal.Kubel
return nil, nil, fmt.Errorf("failed to get absolute path for --dynamic-config-dir=%s", dynamicConfigDir)
}
// get the latest KubeletConfiguration checkpoint from disk, or return the default config if no valid checkpoints exist
c := dynamickubeletconfig.NewController(defaultConfig, dir)
c := dynamickubeletconfig.NewController(dir)
kc, err := c.Bootstrap()
if err != nil {
return nil, nil, fmt.Errorf("failed to determine a valid configuration, error: %v", err)
Expand Down
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