mirror of
https://github.com/VictoriaMetrics/VictoriaMetrics.git
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101 lines
3.9 KiB
Go
101 lines
3.9 KiB
Go
// Copyright 2023, Google Inc.
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// All rights reserved.
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//
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are
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// met:
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//
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// * Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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// * Redistributions in binary form must reproduce the above
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// copyright notice, this list of conditions and the following disclaimer
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// in the documentation and/or other materials provided with the
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// distribution.
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// * Neither the name of Google Inc. nor the names of its
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// contributors may be used to endorse or promote products derived from
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// this software without specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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// Package callctx provides helpers for storing and retrieving values out of
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// [context.Context]. These values are used by our client libraries in various
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// ways across the stack.
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package callctx
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import (
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"context"
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"fmt"
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)
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const (
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// XGoogFieldMaskHeader is the canonical header key for the [System Parameter]
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// that specifies the response read mask. The value(s) for this header
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// must adhere to format described in [fieldmaskpb].
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//
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// [System Parameter]: https://cloud.google.com/apis/docs/system-parameters
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// [fieldmaskpb]: https://google.golang.org/protobuf/types/known/fieldmaskpb
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XGoogFieldMaskHeader = "x-goog-fieldmask"
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headerKey = contextKey("header")
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)
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// contextKey is a private type used to store/retrieve context values.
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type contextKey string
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// HeadersFromContext retrieves headers set from [SetHeaders]. These headers
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// can then be cast to http.Header or metadata.MD to send along on requests.
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func HeadersFromContext(ctx context.Context) map[string][]string {
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m, ok := ctx.Value(headerKey).(map[string][]string)
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if !ok {
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return nil
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}
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return m
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}
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// SetHeaders stores key value pairs in the returned context that can later
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// be retrieved by [HeadersFromContext]. Values stored in this manner will
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// automatically be retrieved by client libraries and sent as outgoing headers
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// on all requests. keyvals should have a corresponding value for every key
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// provided. If there is an odd number of keyvals this method will panic.
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func SetHeaders(ctx context.Context, keyvals ...string) context.Context {
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if len(keyvals)%2 != 0 {
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panic(fmt.Sprintf("callctx: an even number of key value pairs must be provided, got %d", len(keyvals)))
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}
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h, ok := ctx.Value(headerKey).(map[string][]string)
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if !ok {
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h = make(map[string][]string)
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} else {
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h = cloneHeaders(h)
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}
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for i := 0; i < len(keyvals); i = i + 2 {
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h[keyvals[i]] = append(h[keyvals[i]], keyvals[i+1])
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}
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return context.WithValue(ctx, headerKey, h)
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}
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// cloneHeaders makes a new key-value map while reusing the value slices.
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// As such, new values should be appended to the value slice, and modifying
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// indexed values is not thread safe.
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//
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// TODO: Replace this with maps.Clone when Go 1.21 is the minimum version.
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func cloneHeaders(h map[string][]string) map[string][]string {
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c := make(map[string][]string, len(h))
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for k, v := range h {
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vc := make([]string, len(v))
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copy(vc, v)
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c[k] = vc
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}
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return c
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}
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