98 lines
2.5 KiB
Go
98 lines
2.5 KiB
Go
// Package mrun extends mctx to include runtime event hooks and tracking of the
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// liveness of spawned go-routines.
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package mrun
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import (
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"errors"
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"github.com/mediocregopher/mediocre-go-lib/mctx"
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)
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type futureErr struct {
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doneCh chan struct{}
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err error
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}
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func newFutureErr() *futureErr {
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return &futureErr{
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doneCh: make(chan struct{}),
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}
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}
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func (fe *futureErr) get(cancelCh <-chan struct{}) (error, bool) {
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select {
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case <-fe.doneCh:
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return fe.err, true
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case <-cancelCh:
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return nil, false
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}
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}
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func (fe *futureErr) set(err error) {
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fe.err = err
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close(fe.doneCh)
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}
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type ctxKey int
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// Thread spawns a go-routine which executes the given function. When the passed
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// in Context is canceled the Context within all threads spawned from it will
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// be canceled as well.
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//
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// See Wait for accompanying functionality.
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func Thread(ctx mctx.Context, fn func() error) {
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futErr := newFutureErr()
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mctx.GetSetMutableValue(ctx, false, ctxKey(0), func(i interface{}) interface{} {
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futErrs, ok := i.([]*futureErr)
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if !ok {
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futErrs = make([]*futureErr, 0, 1)
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}
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return append(futErrs, futErr)
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})
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go func() {
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futErr.set(fn())
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}()
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}
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// ErrDone is returned from Wait if cancelCh is closed before all threads have
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// returned.
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var ErrDone = errors.New("Wait is done waiting")
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// Wait blocks until all go-routines spawned using Thread on the passed in
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// Context, and all of its children, have returned. Any number of the threads
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// may have returned already when Wait is called.
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//
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// If any of the thread functions returned an error during its runtime Wait will
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// return that error. If multiple returned an error only one of those will be
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// returned. TODO: Handle multi-errors better.
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//
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// If cancelCh is not nil and is closed before all threads have returned then
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// this function stops waiting and returns ErrDone.
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//
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// Wait is safe to call in parallel, and will return the same result if called
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// multiple times in sequence. If new Thread calls have been made since the last
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// Wait call, the results of those calls will be waited upon during subsequent
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// Wait calls.
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func Wait(ctx mctx.Context, cancelCh <-chan struct{}) error {
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// First wait for all the children, and see if any of them return an error
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children := mctx.Children(ctx)
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for _, childCtx := range children {
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if err := Wait(childCtx, cancelCh); err != nil {
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return err
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}
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}
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futErrs, _ := mctx.MutableValue(ctx, ctxKey(0)).([]*futureErr)
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for _, futErr := range futErrs {
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err, ok := futErr.get(cancelCh)
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if !ok {
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return ErrDone
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} else if err != nil {
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return err
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}
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}
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return nil
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}
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