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experimental: adds close notification hook (#1574)
Signed-off-by: Adrian Cole <adrian@tetrate.io>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,63 @@ | ||
| package experimental | ||
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| import ( | ||
| "context" | ||
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| "github.com/tetratelabs/wazero/internal/close" | ||
| ) | ||
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| // CloseNotifier is a notification hook, invoked when a module is closed. | ||
| // | ||
| // Note: This is experimental progress towards #1197, and likely to change. Do | ||
| // not expose this in shared libraries as it can cause version locks. | ||
| type CloseNotifier interface { | ||
| // CloseNotify is a notification that occurs *before* an api.Module is | ||
| // closed. `exitCode` is zero on success or in the case there was no exit | ||
| // code. | ||
| // | ||
| // Notes: | ||
| // - This does not return an error because the module will be closed | ||
| // unconditionally. | ||
| // - Do not panic from this function as it doing so could cause resource | ||
| // leaks. | ||
| // - While this is only called once per module, if configured for | ||
| // multiple modules, it will be called for each, e.g. on runtime close. | ||
| CloseNotify(ctx context.Context, exitCode uint32) | ||
| } | ||
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| // ^-- Note: This might need to be a part of the listener or become a part of | ||
| // host state implementation. For example, if this is used to implement state | ||
| // cleanup for host modules, possibly something like below would be better, as | ||
| // it could be implemented in a way that allows concurrent module use. | ||
| // | ||
| // // key is like a context key, stateFactory is invoked per instantiate and | ||
| // // is associated with the key (exposed as `Module.State` similar to go | ||
| // // context). Using a key is better than the module name because we can | ||
| // // de-dupe it for host modules that can be instantiated into different | ||
| // // names. Also, you can make the key package private. | ||
| // HostModuleBuilder.WithState(key any, stateFactory func() Cleanup)` | ||
| // | ||
| // Such a design could work to isolate state only needed for wasip1, for | ||
| // example the dirent cache. However, if end users use this for different | ||
| // things, we may need separate designs. | ||
| // | ||
| // In summary, the purpose of this iteration is to identify projects that | ||
| // would use something like this, and then we can figure out which way it | ||
| // should go. | ||
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| // CloseNotifyFunc is a convenience for defining inlining a CloseNotifier. | ||
| type CloseNotifyFunc func(ctx context.Context, exitCode uint32) | ||
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| // CloseNotify implements CloseNotifier.CloseNotify. | ||
| func (f CloseNotifyFunc) CloseNotify(ctx context.Context, exitCode uint32) { | ||
| f(ctx, exitCode) | ||
| } | ||
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| // WithCloseNotifier registers the given CloseNotifier into the given | ||
| // context.Context. | ||
| func WithCloseNotifier(ctx context.Context, notifier CloseNotifier) context.Context { | ||
| if notifier != nil { | ||
| return context.WithValue(ctx, close.NotifierKey{}, notifier) | ||
| } | ||
| return ctx | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,27 @@ | ||
| package experimental_test | ||
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| import ( | ||
| "context" | ||
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| "github.com/tetratelabs/wazero/experimental" | ||
| ) | ||
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| var ctx context.Context | ||
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| // This shows how to implement a custom cleanup task on close. | ||
| func Example_closeNotifier() { | ||
| closeCh := make(chan struct{}) | ||
| ctx = experimental.WithCloseNotifier( | ||
| ctx, | ||
| experimental.CloseNotifyFunc(func(context.Context, uint32) { close(closeCh) }), | ||
| ) | ||
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| // ... create module, do some work. Sometime later in another goroutine: | ||
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| select { | ||
| case <-closeCh: | ||
| // do some cleanup | ||
| default: | ||
| // do some more work with the module | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,42 @@ | ||
| package experimental_test | ||
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| import ( | ||
| "context" | ||
| "testing" | ||
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| "github.com/tetratelabs/wazero/experimental" | ||
| "github.com/tetratelabs/wazero/internal/close" | ||
| "github.com/tetratelabs/wazero/internal/testing/require" | ||
| ) | ||
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| // testCtx is an arbitrary, non-default context. Non-nil also prevents linter errors. | ||
| var testCtx = context.WithValue(context.Background(), struct{}{}, "arbitrary") | ||
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| func TestWithCloseNotifier(t *testing.T) { | ||
| tests := []struct { | ||
| name string | ||
| notification experimental.CloseNotifier | ||
| expected bool | ||
| }{ | ||
| { | ||
| name: "returns input when notification nil", | ||
| expected: false, | ||
| }, | ||
| { | ||
| name: "decorates with notification", | ||
| notification: experimental.CloseNotifyFunc(func(context.Context, uint32) {}), | ||
| expected: true, | ||
| }, | ||
| } | ||
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| for _, tt := range tests { | ||
| tc := tt | ||
| t.Run(tc.name, func(t *testing.T) { | ||
| if decorated := experimental.WithCloseNotifier(testCtx, tc.notification); tc.expected { | ||
| require.NotNil(t, decorated.Value(close.NotifierKey{})) | ||
| } else { | ||
| require.Same(t, testCtx, decorated) | ||
| } | ||
| }) | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,13 @@ | ||
| // Package close allows experimental.CloseNotifier without introducing a | ||
| // package cycle. | ||
| package close | ||
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| import "context" | ||
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| // NotifierKey is a context.Context Value key. Its associated value should be a | ||
| // Notifier. | ||
| type NotifierKey struct{} | ||
|
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| type Notifier interface { | ||
| CloseNotify(ctx context.Context, exitCode uint32) | ||
| } |
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