kacerrandClaude Opus 5.5
0a6c8624f3
kvm2's NoCloud seed builder moves to internal/provider/nocloud (exported, with an ErrEmptyName sentinel instead of permanentf) and its keyed locks to internal/provider/keyedlock, tests moved under their existing names. kvm2 behaviour is unchanged. proxmox gains the per-name lock and the pure seed helpers (seedISOName, seedVolID, buildSeed); unlike kvm2 (review finding S5.1), a seed staging failure there is Transient, not Permanent. Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
61 lines
1.4 KiB
Go
61 lines
1.4 KiB
Go
// Package keyedlock provides one-slot semaphores by key, shared by the
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// providers that serialise work per instance name or per cached image
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// (kvm2, proxmox).
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package keyedlock
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import (
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"context"
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"sync"
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)
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// Locks is a set of one-slot semaphores by key: a semaphore rather than a
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// mutex so a waiter can give up with its ctx. Each entry counts the callers
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// holding or waiting for it and is dropped from the map at zero, so the map
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// does not grow with every key ever seen while two waiters on one key still
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// always share one semaphore. The zero value is not usable; call New.
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type Locks struct {
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mu sync.Mutex
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locks map[string]*lock
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}
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type lock struct {
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sem chan struct{}
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refs int
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}
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func New() *Locks {
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return &Locks{locks: make(map[string]*lock)}
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}
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// Acquire takes the lock for key, or gives up with ctx's error. The
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// returned func releases it and must be called exactly once.
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func (k *Locks) Acquire(ctx context.Context, key string) (release func(), err error) {
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k.mu.Lock()
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l, ok := k.locks[key]
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if !ok {
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l = &lock{sem: make(chan struct{}, 1)}
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k.locks[key] = l
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}
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l.refs++
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k.mu.Unlock()
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select {
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case l.sem <- struct{}{}:
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return func() {
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<-l.sem
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k.unref(key, l)
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}, nil
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case <-ctx.Done():
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k.unref(key, l)
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return nil, ctx.Err()
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}
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}
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func (k *Locks) unref(key string, l *lock) {
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k.mu.Lock()
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defer k.mu.Unlock()
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l.refs--
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if l.refs == 0 {
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delete(k.locks, key)
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}
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}
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