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53 lines
1.4 KiB
Go
53 lines
1.4 KiB
Go
// Copyright 2019 Drone.IO Inc. All rights reserved.
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// Use of this source code is governed by the Polyform License
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// that can be found in the LICENSE file.
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package client
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import (
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"context"
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"runtime/debug"
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"sync"
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"git.awesome-for.me/liuzhiguo/drone-go/drone"
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)
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var _ Client = (*SingleFlight)(nil)
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// SingleFlight wraps a Client and limits to a single in-flight
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// request to pull items from the queue.
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type SingleFlight struct {
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Client
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mu sync.Mutex
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}
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// NewSingleFlight returns a Client that is limited to a single in-flight
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// request to pull items from the queue.
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func NewSingleFlight(endpoint, secret string, skipverify bool) *SingleFlight {
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return &SingleFlight{Client: New(endpoint, secret, skipverify)}
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}
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// Request requests the next available build stage for execution.
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func (t *SingleFlight) Request(ctx context.Context, args *Filter) (*drone.Stage, error) {
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// if the context is canceled there is no need to make
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// the request and we can exit early.
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select {
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case <-ctx.Done():
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return nil, ctx.Err()
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default:
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}
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// if is critical to unlock the mutex when the function
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// exits. although a panic is unlikely it is critical that
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// we recover from the panic to avoid deadlock.
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defer func() {
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if r := recover(); r != nil {
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debug.PrintStack()
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}
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t.mu.Unlock()
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}()
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// lock the mutex to ensure only a single in-flight
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// request to request a resource from the server queue.
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t.mu.Lock()
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return t.Client.Request(ctx, args)
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}
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