103 lines
2.4 KiB
Go
103 lines
2.4 KiB
Go
package batch
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import (
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"errors"
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"sync"
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"github.com/lightningnetwork/lnd/kvdb"
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)
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// errSolo is a sentinel error indicating that the requester should re-run the
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// operation in isolation.
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var errSolo = errors.New(
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"batch function returned an error and should be re-run solo",
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)
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type request struct {
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*Request
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errChan chan error
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}
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type batch struct {
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db kvdb.Backend
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start sync.Once
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reqs []*request
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clear func(b *batch)
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locker sync.Locker
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}
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// trigger is the entry point for the batch and ensures that run is started at
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// most once.
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func (b *batch) trigger() {
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b.start.Do(b.run)
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}
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// run executes the current batch of requests. If any individual requests fail
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// alongside others they will be retried by the caller.
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func (b *batch) run() {
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// Clear the batch from its scheduler, ensuring that no new requests are
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// added to this batch.
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b.clear(b)
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// If a cache lock was provided, hold it until the this method returns.
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// This is critical for ensuring external consistency of the operation,
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// so that caches don't get out of sync with the on disk state.
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if b.locker != nil {
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b.locker.Lock()
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defer b.locker.Unlock()
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}
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// Apply the batch until a subset succeeds or all of them fail. Requests
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// that fail will be retried individually.
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for len(b.reqs) > 0 {
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var failIdx = -1
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err := kvdb.Update(b.db, func(tx kvdb.RwTx) error {
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for i, req := range b.reqs {
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err := req.Update(tx)
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if err != nil {
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failIdx = i
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return err
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}
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}
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return nil
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}, func() {
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for _, req := range b.reqs {
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if req.Reset != nil {
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req.Reset()
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}
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}
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})
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// If a request's Update failed, extract it and re-run the
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// batch. The removed request will be retried individually by
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// the caller.
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if failIdx >= 0 {
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req := b.reqs[failIdx]
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// It's safe to shorten b.reqs here because the
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// scheduler's batch no longer points to us.
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b.reqs[failIdx] = b.reqs[len(b.reqs)-1]
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b.reqs = b.reqs[:len(b.reqs)-1]
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// Tell the submitter re-run it solo, continue with the
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// rest of the batch.
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req.errChan <- errSolo
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continue
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}
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// None of the remaining requests failed, process the errors
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// using each request's OnCommit closure and return the error
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// to the requester. If no OnCommit closure is provided, simply
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// return the error directly.
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for _, req := range b.reqs {
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if req.OnCommit != nil {
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req.errChan <- req.OnCommit(err)
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} else {
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req.errChan <- err
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}
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}
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return
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}
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}
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