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Merge pull request #78 from karlseguin/control_stop
Refactor control messages + Stop handling
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,110 @@ | ||
| package ccache | ||
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| type controlGC struct { | ||
| done chan struct{} | ||
| } | ||
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| type controlClear struct { | ||
| done chan struct{} | ||
| } | ||
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| type controlStop struct { | ||
| } | ||
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| type controlGetSize struct { | ||
| res chan int64 | ||
| } | ||
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| type controlGetDropped struct { | ||
| res chan int | ||
| } | ||
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| type controlSetMaxSize struct { | ||
| size int64 | ||
| done chan struct{} | ||
| } | ||
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| type controlSyncUpdates struct { | ||
| done chan struct{} | ||
| } | ||
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| type control chan interface{} | ||
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| func newControl() chan interface{} { | ||
| return make(chan interface{}, 5) | ||
| } | ||
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| // Forces GC. There should be no reason to call this function, except from tests | ||
| // which require synchronous GC. | ||
| // This is a control command. | ||
| func (c control) GC() { | ||
| done := make(chan struct{}) | ||
| c <- controlGC{done: done} | ||
| <-done | ||
| } | ||
|
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| // Sends a stop signal to the worker thread. The worker thread will shut down | ||
| // 5 seconds after the last message is received. The cache should not be used | ||
| // after Stop is called, but concurrently executing requests should properly finish | ||
| // executing. | ||
| // This is a control command. | ||
| func (c control) Stop() { | ||
| c.SyncUpdates() | ||
| c <- controlStop{} | ||
| } | ||
|
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| // Clears the cache | ||
| // This is a control command. | ||
| func (c control) Clear() { | ||
| done := make(chan struct{}) | ||
| c <- controlClear{done: done} | ||
| <-done | ||
| } | ||
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| // Gets the size of the cache. This is an O(1) call to make, but it is handled | ||
| // by the worker goroutine. It's meant to be called periodically for metrics, or | ||
| // from tests. | ||
| // This is a control command. | ||
| func (c control) GetSize() int64 { | ||
| res := make(chan int64) | ||
| c <- controlGetSize{res: res} | ||
| return <-res | ||
| } | ||
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| // Gets the number of items removed from the cache due to memory pressure since | ||
| // the last time GetDropped was called | ||
| // This is a control command. | ||
| func (c control) GetDropped() int { | ||
| res := make(chan int) | ||
| c <- controlGetDropped{res: res} | ||
| return <-res | ||
| } | ||
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| // Sets a new max size. That can result in a GC being run if the new maxium size | ||
| // is smaller than the cached size | ||
| // This is a control command. | ||
| func (c control) SetMaxSize(size int64) { | ||
| done := make(chan struct{}) | ||
| c <- controlSetMaxSize{size: size, done: done} | ||
| <-done | ||
| } | ||
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| // SyncUpdates waits until the cache has finished asynchronous state updates for any operations | ||
| // that were done by the current goroutine up to now. | ||
| // | ||
| // For efficiency, the cache's implementation of LRU behavior is partly managed by a worker | ||
| // goroutine that updates its internal data structures asynchronously. This means that the | ||
| // cache's state in terms of (for instance) eviction of LRU items is only eventually consistent; | ||
| // there is no guarantee that it happens before a Get or Set call has returned. Most of the time | ||
| // application code will not care about this, but especially in a test scenario you may want to | ||
| // be able to know when the worker has caught up. | ||
| // | ||
| // This applies only to cache methods that were previously called by the same goroutine that is | ||
| // now calling SyncUpdates. If other goroutines are using the cache at the same time, there is | ||
| // no way to know whether any of them still have pending state updates when SyncUpdates returns. | ||
| // This is a control command. | ||
| func (c control) SyncUpdates() { | ||
| done := make(chan struct{}) | ||
| c <- controlSyncUpdates{done: done} | ||
| <-done | ||
| } |
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