66 lines
1.5 KiB
Markdown
66 lines
1.5 KiB
Markdown
Locker
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=====
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locker provides a mechanism for creating finer-grained locking to help
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free up more global locks to handle other tasks.
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The implementation looks close to a sync.Mutex, however the user must provide a
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reference to use to refer to the underlying lock when locking and unlocking,
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and unlock may generate an error.
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If a lock with a given name does not exist when `Lock` is called, one is
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created.
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Lock references are automatically cleaned up on `Unlock` if nothing else is
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waiting for the lock.
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## Usage
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```go
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package important
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import (
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"sync"
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"time"
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"github.com/docker/docker/pkg/locker"
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)
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type important struct {
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locks *locker.Locker
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data map[string]interface{}
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mu sync.Mutex
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}
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func (i *important) Get(name string) interface{} {
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i.locks.Lock(name)
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defer i.locks.Unlock(name)
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return data[name]
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}
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func (i *important) Create(name string, data interface{}) {
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i.locks.Lock(name)
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defer i.locks.Unlock(name)
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i.createImportant(data)
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s.mu.Lock()
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i.data[name] = data
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s.mu.Unlock()
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}
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func (i *important) createImportant(data interface{}) {
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time.Sleep(10 * time.Second)
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}
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```
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For functions dealing with a given name, always lock at the beginning of the
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function (or before doing anything with the underlying state), this ensures any
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other function that is dealing with the same name will block.
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When needing to modify the underlying data, use the global lock to ensure nothing
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else is modfying it at the same time.
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Since name lock is already in place, no reads will occur while the modification
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is being performed.
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