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Volumes that are provisioned with `VolumeMode: Block` often have a MetrucsProvider interface declared in their type. However, the MetricsProvider should implement a GetMetrics() function. In the cases where the storage drivers do not implement GetMetrics(), a panic can occur. Usual type-assertions are not sufficient in this case. All assertions assume the interface is present. There is no straight forward way to verify that a valid GetMetrics() function is provided. By adding SupportsMetrics(), storage driver implementations require careful reviewing for metrics support.
36 lines
1.1 KiB
Go
36 lines
1.1 KiB
Go
/*
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Copyright 2014 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 volume
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var _ MetricsProvider = &MetricsNil{}
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// MetricsNil represents a MetricsProvider that does not support returning
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// Metrics. It serves as a placeholder for Volumes that do not yet support
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// metrics.
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type MetricsNil struct{}
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// SupportsMetrics returns false for the MetricsNil type.
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func (*MetricsNil) SupportsMetrics() bool {
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return false
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}
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// GetMetrics returns an empty Metrics and an error.
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// See MetricsProvider.GetMetrics
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func (*MetricsNil) GetMetrics() (*Metrics, error) {
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return &Metrics{}, NewNotSupportedError()
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}
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